study of a process chain for additive manufactured aisi 316 l … · 2019-05-17 · thesis report....
TRANSCRIPT
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SCUOLA DI INGEGNERIA INDUSTRIALE E DELL’INFORMAZIONE
Laurea Magistrale In Ingegneria Meccanica
Study of A Process Chain for Additive Manufactured AISI 316 L
stainless steel tubes
Academic Year 18/19
supervisor: prof. Massimilano Pietro Giovanni ANNONI
co-supervisor: dr. Valentina FURLAN
Ali HAIDER 883074
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ACKNOWLEDGEMENT
All praises to Almighty Allah for the strengths and HIS blessings in completion of this
thesis report.
I express my gratitude to my thesis supervisor Professor Massimiliano Pietro Giovanni
Annoni, of the Mechanical Engineering Department for the technical support provided
during the development of this master thesis.
I offer my appreciation to Dr. Valentina Furlan and Stefano Petro for supporting me
with their advice during the experimental tests. I take this opportunity to express
gratitude to all the laboratory members of mechanical department at Politecnico di
Milano, especially Ing. Pasquale Aquilino who was always ready to offer me his
support.
I would also like to thank TENOVA for helping me in heat treatment process and Marco
Camagni of GF for helping us in substrate removal using Wire EDM.
I would like to thank my colleague Mr. Abdul Haseeb for being with me during the last
two years at Politecnico di Milano.
Finally, I take this opportunity to express my profound gratitude to my honorable father,
Mr. Khalid Javed, my mother, Mrs. Fakhra Khalid, my wife, Hajra Fatima Khalid and
my younger brother and sister for providing me with unfailing support and continuous
encouragement throughout my degree. This accomplishment would not have been
possible without them.
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TABLE OF CONTENTS
Abstract…………………………………………………………………………………...............6
Introduction…………………………………………………………………………………….….8
1 STATE OF THE ART
1. 1 Manufacturing…………………………………………………………………………….…10
1.1.1 Classification of Manufacturing
1.1.2 Selection of Manufacturing Process
1. 2 Additive Manufacturing……………………………………………………………….…….11
1.2.1 Classification of Additive Manufacturing
Powder Bed Fusion ……………………………………………………………………….….….12
Direct Energy Deposition……………………………………………………………………..….13
Processing Parameters
Merit and Demerit of Additive Manufacturing ……………………………………………..…..14
1. 3 Microstructure of Additive Manufacturing component……………………………….…..15
Microstructure of 316 L fabricated by Additive manufacturing technology
Impact of build direction on the microstructure
Impact of Laser Power on the microstructure
1.4 Mechanical Properties……………………………………………………………….……….17
Impact of build direction on the tensile properties of 316 L
Impact of Laser Power on the tensile properties of 316 L
Impact of Porosity on the mechanical properties
1.5 Machinability of Additive Manufactured Products…………………………………………20
1.5.1 Effect of cutting speed and feed rate on the cutting force…………………….………..21
1.5.2 Effect of cutting speed, feed rate and depth of cut on the surface
roughness………………………………………………………………………………….……….23
1.5.3 Residual stresses in Additive Manufactured components and effect of processing
parameters on tool wear…………………………………………………………………………..31
2 AIM OF THE WORK…………………………………………………………………………….34
3 MATERIAL AND METHODOLOGY…………………………………………………….….....36
3.1 Process Chain…………………………………………………………………………..….…..36
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3.2 Material used…………………………………………………………………………………..38
3.3 Methodology/ Setup employed………………………………………………………………38
3.3.1 Manufacturing of 316 L stainless steel cylindrical tube using ADDITUBE Cells.........38
3.3.2 Heat Treatment Methodology………………………………………………………….......40
3.3.3 Wire EDM for substrate Removal………………………………………………………….40
3.3.4 Turning operation…………………………………………………………………………….41
3.4 Instruments for evaluation of parts quality…………………………………………………..43
3.4.1 Measurement of the Parts…………………………………………………………………..44
3.4.2 Roughness Measurement…………………………………………………………………..44
3.4.3 Measurement of Hardness………………………………………………………………….47
4 PRELIMINARY TESTS………………………………………………………………………….50
4.1 Results of Preliminary Tests…………………………………………………………………..50
4.2 Selected Parameters…………………………………………………………………………..52
5 RESULTS…………………………………………………………………………………………54
5.1 Results of Coordinate Measuring Machine System (CMMS)……………………………..54
5.1.1 Effect of Cylinder Height and Heat Treatment on External Roundness of DED 316 L
cylindrical tubes…………………………………………………………………………………….54
5.1.2 Effect of Cylinder Height and Heat Treatment on Internal Roundness of DED 316 L
cylindrical tubes.…………………………………………………………………………………….61
5.1.3 Effect of cylinder height and heat treatment on the internal diameter of DED 316 L
stainless steel cylindrical tubes.…………………………………………………………………..67
5.1.4 Effect of cylinder height and heat treatment on the external diameter of DED 316 L
Cylindrical tubes.……………………………………………………………………………………75
5.1.5 Effect of cylinder height and heat treatment on the internal cylindricity of DED 316 L
Cylindrical tubes.……………………………………………………………………………………83
5.1.6 Effect of cylinder height and heat treatment on the external cylindricity of DED 316 L
Cylindrical tubes…………………………………………………………………………………….87
REDUCED MODEL:………………………………………………………………………………..90
5.1.7 Effect of Cylinder height, Heat Treatment, substrate removal, turning on the external
roundness of DED 316 L cylindrical tubes………………………………………………………90
5.1.8 Effect of Cylinder height, Heat Treatment, substrate removal, turning on the internal
roundness of DED 316 L cylindrical tubes………………………………………………………98
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5.1.9 Effect of Cylinder height, Heat Treatment, substrate removal, turning on the external
cylindricity of DED 316 L stainless steel cylindrical tubes…………………………………….103
5.1.10 Effect of Cylinder height, Heat Treatment, substrate removal, turning on the internal
cylindricity of DED 316 L stainless steel cylindrical tubes……………………………………..108
5.2 ROUGHNESS…….…………………………………………………....................................113
5.2.1Effect of Position, orientation, internal and external surface on the roughness of DED 316
L cylindrical tube before Heat Treatment………………………………………………………..113
5.2.2Effect of Position, orientation, internal and external surface on the roughness of DED 316
L cylindrical tube after Heat Treatment…………………………………………………………..115
5.2.3Effect of position, internal / external part and heat treatment on the mean roughness:.117
5.2.4 Effect of Heat Treatment and External/ internal factors on the mean roughness of each
specimen in terms of position and orientation…………………………………………………..119
5.2.5 Effect of Heat Treatment on the External Roughness of DED 316 L tubes………......124
5.2.6 Effect of Heat Treatment on the Internal Roughness of DED 316 L tubes……………125
5.2.7Effect of cutting speed and feed rate on the External Roughness……………………….126
5.2.8 Effect of cutting speed and feed rate on the Internal Roughness……………………….131
5.3 MICRO HARDNESS…………………………………………………………………............135
5.3.1Effect of position and Heat Treatment on the Micro Hardness of Specimen…………....135
5.3.2 Effect of cutting speed and feed rate on the micro hardness of DED 316 L cylindrical
tubes………………………………………………………………………………………………...139
6 CONCLUSIONS & FINAL RECOMMENDATIONS…………………...…...………………..143
BIBLIOGRAPHY…………..…………….………………………………………………………...145
APPENDIX 1 HARDNESS RESULTS…………………………………………………………..148
APPENDIX 2 ROUGHNESS RESULTS…………………………………………………..........149
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ABSTRACT
Among the additive manufacturing techniques, Direct Energy Deposition (DED), is
widely used to fabricate complex three-dimensional metallic components using a layer
by layer approach. The major drawback of components manufactured using this
technique is the surface quality, which is generally beyond the acceptable range.
Therefore, there is a need for hybrid manufacturing, including additive manufacturing
and finish machining processes to be developed and implemented in the industry.
In my study a complete process chain from fabrication, heat treatment to finish
machining operation of additive manufactured DED 316 L stainless steel tubes has
been studied. A qualitative analysis which involves the measurement of dimensional
characteristics of the tubes in terms of diameter, roundness, cylindricity; the roughness
measurement of the tubes and the determination of micro hardness of additive
manufactured DED 316 L tubes has been carried out at each of the following step: as
built, heat treated and after machining. The experimental study reveals that the DED
316 L tubes produced were not perfect cylinders and there was some conicity in the
tubes. Moreover, heat treatment had a positive impact on the dimensional and surface
characteristics of the DED 316 L tubes since both the roundness and surface
roughness of DED 316 L tubes reduced. The surface roughness and micro hardness
at position close to the substrate was found to be significantly different from the
roughness and to the micro hardness values at the middle and close to the edge of
additive manufactured DED 316 L stainless steel tubes. The experimental study
reveals that finish machining resulted in a lower surface roughness and increased
micro hardness of additive manufactured DED 316 L stainless steel cylindrical tubes.
A design of analysis experiment was conducted to determine the effect of machining
parameters such as cutting speed and feed rate on the surface roughness and micro
hardness of additive manufactured DED 316 L stainless steel cylindrical tube. It was
found out that feed rate had a major influence on the surface roughness and micro
hardness of DED 316 L stainless steel tubes.
The experimental results suggested that high cutting speed and feed rate results in
poor surface finish and increased micro hardness of additive manufactured DED 316
L stainless steel tubes.
Keywords: Process Chain, additive manufactured, DED 316 L, heat treatment,
finish machining, dimensional characteristics, roughness measurement, hardness
measurement
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ABSRTACT (ITALIAN VERSION):
Tra le tecniche di produzione additiva, Direct Energy Deposition (DED), è ampiamente utilizzato per fabbricare complessi componenti metallici tridimensionali usando un approccio strato per strato. Il principale inconveniente dei componenti fabbricati usando questa tecnica è la qualità della superficie, che è generalmente oltre l'intervallo accettabile. Pertanto, vi è la necessità di una produzione ibrida, compresi i processi di produzione additiva e di finitura, da sviluppare e implementare nel settore. Nel mio studio è stata studiata una catena di processo completa dalla fabbricazione,
trattamento termico per finire la lavorazione di tubi in acciaio inossidabile DED 316 L
additivi prodotti. Un'analisi qualitativa che prevede la misurazione delle caratteristiche
dimensionali dei tubi in termini di diametro, rotondità, cilindricità; la misurazione della
rugosità dei tubi e la determinazione della microdurezza delle provette DED 316 L
additive sono state eseguite in ciascuna delle seguenti fasi: come costruito, sottoposto
a trattamento termico e dopo la lavorazione. Lo studio sperimentale rivela che i tubi
DED 316 L prodotti non erano cilindri perfetti e c'era una certa conicità nei tubi. Inoltre,
il trattamento termico ha avuto un impatto positivo sulle caratteristiche dimensionali e
superficiali dei tubi DED 316 L poiché sia la rotondità che la rugosità superficiale dei
tubi DED 316 L sono stati ridotti. La rugosità superficiale e la microdurezza in
posizione vicino al substrato sono risultate significativamente diverse dalla rugosità e
ai valori di micro durezza al centro e vicino al bordo dei tubi di acciaio inossidabile
DED 316 L additivi fabbricati. Lo studio sperimentale rivela che la lavorazione delle
finiture ha prodotto una minore rugosità superficiale e una maggiore durezza micro
dei tubi cilindrici in acciaio inossidabile DED 316 L additivi prodotti. È stato condotto
un progetto di esperimento di analisi per determinare l'effetto di parametri di
lavorazione quali velocità di taglio e velocità di avanzamento sulla rugosità superficiale
e micro durezza del tubo cilindrico in acciaio inossidabile DED 316 L additivo
fabbricato. È stato scoperto che la velocità di alimentazione ha avuto un'influenza
maggiore sulla rugosità superficiale e sulla microdurezza dei tubi in acciaio
inossidabile DED 316 L
I risultati sperimentali hanno suggerito che un'elevata velocità di taglio e velocità di avanzamento si traducono in una scarsa finitura superficiale e una maggiore durezza micro dei tubi in acciaio inossidabile DED 316 L additivi prodotti.
Parole chiave: catena di processo, prodotto additivo, DED 316 L, trattamento
termico, lavorazione delle finiture, caratteristiche dimensionali, misurazione della
rugosità, misurazione della durezza
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INTRODUCTION
Austenitic stainless steel (AISI 316 L) material provides excellent corrosion resistance
and is widely used in various applications of petrochemical (oil and gas), chemical,
and bio medical industries. Usually, Stainless steel components are fabricated using
traditional manufacturing processes of casting, forging, extrusion etc. These
technologies are time consuming and they do not allow the production of complex
components. Therefore, in order to improve the situation, additive manufacturing
technologies are becoming more and more popular. Direct Energy Deposition (DED),
is a type of additive manufacturing process that is used to fabricate complex three-
dimensional (3D) metallic and functional objects, by the layer-wise addition of material
based on predefined computer aided design (CAD) data. In DED process, a relatively
high-powered laser source is used to create a molten pool atop of the substrate
surface in the presence of an inert gas, while the wire or powder particles are injected
simultaneously into the melt pool. The final parts are then built with a layer by layer
approach using CAD model. DED technology possesses the advantages of design
flexibility and the capability to produce complex metallic geometries.
Although additive manufacturing processes provides many advantages as compared
to conventional manufacturing techniques, one of the major drawbacks of this
technology is the poor surface quality. The surface quality of additive manufactured
components is influenced by many factors such as built orientation, laser parameters
including the laser power, scanning speed, hatch distance and the size of powder
particles. Since the functionality of additive manufactured parts highly depends on the
geometric and dimensional accuracy, therefore the surface characteristics or
approaches to enhance the surface characteristics of parts fabricated by additive
manufacturing needs to be considered. Therefore, in order to improve the surface
characteristics, hybrid manufacturing is adopted in which components fabricated by
additive manufacturing are subjected to finish machining operation. Finish machining
processes includes either turning or milling operations, which are selected based on
the geometry of the additive manufactured parts.
The effect of finish turning operation on the surface characteristics of additive
manufactured DED 316 L stainless steel components yet remains to be investigated.
In my study, a complete process chain has been developed starting from the
fabrication of additive manufactured DED 316 L stainless steel tubes to heat treatment
and afterwards finish turning operation, both external and internal turning operation,
was carried out. A qualitative analysis was carried out at each step: right after
deposition, after heat treatment and after finish machining on each of the DED 316L
tube. For each step the qualitative analysis involves the measurement of the
dimensional characteristics of the tubes in terms of the external and internal diameter,
external and internal roundness, external and internal cylindricity; the measurement of
roughness of DED 316 L tubes and the determination of the mechanical properties in
terms of microhardness of additive manufactured DED 316 L stainless steel cylindrical
tubes.
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The tubes were fabricated using Direct Energy Deposition technology. The tubes were
then subjected to heat treatment using a vertical furnace under vacuum at TENOVA.
Wire EDM process was used to remove the substrate from additive manufactured DED
316 L stainless steel tubes. In order to improve the surface characteristic and the
mechanical properties of additive manufactured 316 L tubes, finish machining
operation including external and internal turning operation was carried out on the
tubes. The dimensional characteristics including (diameter, roundness and cylindricity)
of the DED 316 L stainless steel tubes were measured at each step: right after
deposition, after heat treatment, after substrate removal and after machining using
Zeiss Prismo VAST HTG Coordinate Measurement Machine System (CMMS). A
mechanical profilometer was used to measure the external and internal roughness of
additive manufactured DED 316 L stainless steel tubes at 3 different positions (1: close
to the substrate, 2: at the middle, 3: close to the edge) and along the 4 orientations of
the tube for each step: i.e. as built, after heat treatment and after machining. The
microhardness measurements for additive manufactured DED 316 L stainless steel
tubes were acquired at each of the 3 steps i.e. as built, after heat treatment and after
machining by using Vickers hardness machine at 3 different positions (1: close to the
substrate, 2: at the middle and 3 at the edge).
A design of analysis experiment was then conducted to analyze the impact of heat
treatment, batch order, cylinder height and blocking factor day on the dimensional
characteristics of additive manufactured DED 316 L stainless steel cylindrical tubes.
A Multiway ANOVA analysis was conducted to determine the impact of heat treatment,
position and orientation on the surface roughness of additive manufactured DED 316
L stainless steel cylindrical tubes. A 2k factorial design of analysis experiment was
carried out in order to determine the impact of machining parameters i.e. cutting speed
and feed rate on the surface roughness and microhardness of machined DED 316 L
stainless steel tubes.
The experimental results suggested that the surface roughness and microhardness at
position close to the substrate was found to be significantly different from the surface
roughness and the microhardness value at the middle and close to the edge of additive
manufactured DED 316 L stainless steel tubes. The result of my study reveals that
heat treatment and finish turning process had significantly improved the surface
characteristics and microhardness of additive manufactured DED 316 L stainless steel
tubes. Moreover, feed rate had a major impact on the surface roughness and on the
microhardness of additive manufactured DED 316 L stainless steel tubes. It was found
out that high cutting speed and high feed rate results in poor surface finish and
increased microhardness of additive manufactured DED 316 L stainless steel tubes.
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1 STATE OF THE ART
1.1 MANUFACTURING
The term manufacturing originates from the latin word “manufactus”, which means
“made by hand”. Manufacturing involves the conversion of raw material into useful
products by using resources including manpower, material, machinery, energy etc. In
the recent years, manufacturing has undergone a major shift in technology. The
transformation phase of manufacturing includes mechanization, automation and then
computerization.
1.1.1 Classification of manufacturing process
Manufacturing process can be classified into
• Traditional Manufacturing process
• Nontraditional Manufacturing process
Figure 1-1. Classification of Manufacturing Process [1]
1.1.2 Selection of manufacturing process
The selection of manufacturing process depends on many factors. Kalpakjian et al.
(2006) [1] detailed that the selection of manufacturing process depends on many
factors which include the desired shape of the part and its material properties for
performance expectations.
In the article by Badiru et al. (2017) [2], the author described that the selection process
depends on mechanical properties which includes strength, toughness, ductility,
hardness, elasticity, fatigue, creep; physical properties of density , specific heat,
thermal conductivity and expansion , melting point; electrical properties and chemical
properties of corrosion, oxidation, degradation, toxicity and flammability. The author
emphasized that manufacturing properties of materials are also vital, because it is the
manufacturing properties that determines whether the material can be cast, deformed,
machined or heat treated into the desired shape.
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1.2 ADDITIVE MANUFACTURING
Additive Manufacturing processes are used to build complex parts progressively
through layer by layer deposition of the material using a three-dimensional (3D) CAD
model.
In the ASTM, “ASTM F2792-12a, Standard Terminology for Additive Manufacturing
Technologies” [3] , the ASTM F42 committee defined additive manufacturing as “The
process of joining materials to make objects from 3D model data, usually layer upon
layer, as opposed to the subtractive manufacturing methodologies, such as
traditional machining “.
1.2.1 Additive manufacturing technologies can be classified as
Figure 1-2. Classification of Additive Manufacturing technologies [4]
In the article by Udoriu (2014) [4], the author detailed the various additive
manufacturing technologies that are used for manufacturing super alloys. Udoriu in
article [4] and Levy et al. (2003) in article [5], the author explained the classification of
additive manufacturing technologies. Indirect additive manufacturing technologies
involve no, or partial melting of the material and they are followed by post processing
and infiltration operation in order to increase the density of the final part. While the
Direct additive manufacturing technologies usually involve complete melting of the
material and they obtain final properties from the machine. Hybrid technologies are
the combination of direct AM and traditional manufacturing technologies.
Steps in Additive Manufacturing
Additive manufacturing technologies involves 3 steps:
• Preprocessing:
• Processing:
• Post processing
In the Preprocessing stage, an STL file is imported into the software, afterwards
orientation of the part and the simulation of the manufacturing process layer by layer
is carried out.
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The Processing stage involves printing of the parts layer by layer from bottom to the
top. Once the printing is completed, the part is given specific time so that the part is
consolidated.
Post processing involves the removal of the part from the platform, heat treatment,
sandblasting etc.
Figure 1-3. Metal Additive Manufacturing Process [4]
Additive Manufacturing process uses energy sources such as laser, electron beam
electric arc etc. to consolidate the feed stock material which could be wire, powder or
sheet into dense metallic part by melting and solidification. For the Additive
manufacturing of metallic parts, Direct Energy Deposition (DED) and Powder bed
fusion (PBF) technologies are widely used. In the article by Thompson et al. (2015)
[6], and the article by Debroy et al.(2018) [7] “ Additive Manufacturing of Metallic
components- Process , structure and Properties” , the authors described Powder bed
fusion and Direct Energy Deposition process.
Powder Bed Fusion
Powder Bed fusion produces metallic parts through the height wise movement of table,
which consists of a uniformly distributed layer of metallic powder that is selectively
melted by using a laser beam. In the powder bed fusion (PBF) technology, a uniform
bed of powder is deposited onto the table, and then using laser beam, specific regions
of the bed are melted in order to generate single layer of the part. Once a single layer
is completed, the height of powder bed is lowered in correspondence to the height of
the deposited layer and a new bed of powder is deposited. The process is repeated
until we obtain the final part. In order to reduce the oxidation rate of the part during the
build, an inert gas, usually argon, is used. The part is usually fabricated on the
substrate and the finished part needs to be sheared off from the substrate after the
AM process.
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Figure 1-4. Powder Bed Fusion [6]
Direct Energy Deposition
Direct Energy deposition (DED) using different nozzles involves the feeding of the
wire stock or powder material that is directly deposited at the work site along with
simultaneous irradiation of a laser beam. The deposited powder particles are then
melted by the thermal energy provided by the laser beam. As a result, a molten pool
of liquid metal is created. DED process involves two different gases. A shielding gas
is used to prevent the oxidation of the molten metal and a carrier gas is used to carry
the powder stream into the molten pool. After the completion of the deposition of single
layer, the substrate or build plate is moved relative to the deposition head and the
process is repeated as shown in figure 1.5. Thermal monitoring can be done by
infrared cameras. Thompson et al. (2015) [6], and the article by Debroy et al.(2018)
[7]
Figure 1-5. Blown Powder Direct Laser Deposition [6]
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The quality of final part depends on several operating factors. In the article by
Thompson et al. (2015) [6] the author detailed that the final product of the part depends
on following factors.
• Laser traverse speed
• Laser scanning pattern
• Laser Power
• Laser beam diameter
• Powder feed rate
• Hatch spacing.
The laser power is the total power emitted from the laser source. The laser power is
typically of the order of 100-5000 W and the beam diameter is of the order of 1 mm or
more. In DED process, a fraction of the total heat is spent to heat the powder particles
as they emerge from nozzle and travel through the beam. The remaining energy then
impinges on the deposit surface and creates molten metal pool. The laser traverse
speed represents the time taken by DLD process to produce the geometry of the part
and is typically of the order of 1-20 mm/s and also bigger than it. The laser scanning
pattern is used for the laser position and height wise positioning of the substrate.
Thompson et al. (2015) [6]
Debroy et al. (2018) [7] detailed the type and properties of feedstock material used in
Direct Energy Deposition (DED) process. Alloy powders having range between 45µm-
120µm are commonly used as feed stock material in additive manufacturing
technologies because they are easy to feed, provide controlled melting, can reduce
the entrapment of inert gas within the melt pool so that a final part with less porosity is
produced. The quality of additive manufactured parts depends on the characteristics
of the powder which include shape, size distribution, surface morphology, composition
and flowability of the powders. The author explained that the quality of feed stock
material depends on their manufacturing process. Usually GAS atomization process,
Rotary atomization process, Plasma rotating electrode process and Water Atomization
process are used to produce feed stock material for DED process.
Additive manufacturing process has several advantages over conventional
manufacturing processes (Debroy et al. [7] ).They include:
• Additive manufacturing processes allow the production of complex and
customized parts directly from their design without the need of expensive
tooling or forms, such as punches, dies or molds etc.
• Complex parts can be made in one step eliminating the limitation of
conventional processing methods (straight cuts, rounds, holes)
• There is a significant reduction in the part count, because additive
manufacturing processes reduces the need to assemble multiple components.
• The additive nature of the process allows components to be manufactured with
much less raw material wastage that would ultimately reduce the material costs.
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• Since, additive manufacturing processes offers wide range of flexibility,
therefore the parts can be produced on demand and it reduces the inventory of
spare parts and decreases the lead time for critical components.
There are some demerits associated to the additive manufacturing technology. Debroy
et al. (2018) [7] , the author explained some of the disadvantage of additive
manufacturing technology. They include:
• Loss of alloying element
• Porosity and lack of fusion defects
• Surface Roughness
• Cracking and delamination
• Cost
1.3 MICROSTRUCTURE
The materials that are manufactured using Laser additive technique have specific
macro and micro structure and due to which the properties of materials are significantly
different from the part manufactured using conventional technologies.
In the study by Zietala et al. [8] the author explained the microstructure, mechanical
properties and corrosion resistance of 316 L fabricated by LENS technique. The
macroscopic structure of additive manufactured 316 L stainless steel observed,
indicates that there was no evidence of macrocracks, pores and un melted powder
material. The overlapping path formed coherent connection between the sample and
the substrate. No heat affected zone (HAZ) was observed in the substrate.
Figure 1-6. Block sample (a) and optical macrostructure (b) of 316 L using LENS [8]
The microscopic structure reveals the presence of elongated fine grains of austenite.
The grains appear to be oriented along the direction of thermocapillary convection in
the melted pool and heat dissipation. The sub grain boundaries were found to be
enriched with Cr and Mo and the Ni content was reduced. This results in the formation
of intercellular delta ferrite at the sub grain boundaries which is unusual in the wrought
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part. The microscopic observation indicates the presence of austenite and delta ferrite
phase.
Figure 1-7. Microstructure of 316 L using LENS: fine grain structure (a) the island of elongated grain (b and c) formed with fine grains (d) [8]
The building direction, which is the acute angle between the longer axis of the
fabricated sample and the horizontal plane had significant impact on the
microstructure of parts produced by Direct Energy Deposition (DED) process.
Guo et al. (2017) [9] the author described the impact of build direction, 0 degree and
90 degree, on the microstructure of the 316 L stainless steel produced by direct laser
deposition. The microstructure of the additive manufactured 316 L stainless steel part
at build direction of 0 degree was homogeneous and no pores were present. Rapid
solidification because of high temperature gradient and rapid cooling results in refined
microstructure. There was no specific orientation of grain growth. During solidification,
the microstructure in build direction of 90 degree represents an epitaxial dendrite grain
growth. This was due to the high temperature gradient between the molten pool and
the previous deposited zone.
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Figure 1. 8: Micrographs of AM stainless steel at build direction (a), (b), build direction of 0 degree,(c) and (d) at build direction of 90. (e) enlarged view of the microstructure corresponding to (b) [9]
Laser power impacts the microstructure of the part produced by direct energy
deposition. In the article by Wang et al. (2016) [10], the author detailed the impact of
heat input on the microstructure and the mechanical properties of 304 L produced by
Direct Energy Deposition (DED). The author observed that, laser power and grain size
had a direct relationship. The grains observed from low power were smaller and fine.
With the increase of laser power, the grain size becomes coarser. This is due to the
fact that by increasing the laser power, the melt pool gets larger, and it results in low
thermal gradient and slow cooling as compared with low power
1.4 MECHANICAL PROPERTIES
The materials fabricated using Laser additive technology showed anisotropy in the
mechanical properties. This was confirmed by Zietala et al [8], in which the LENS
fabricated stainless steel 316 L was characterized by anisotropy in the mechanical
properties. It was found that the Yield strength and Ultimate tensile strength was higher
when measured parallel to the layers than those measured perpendicular to the layer,
while an inverse relationship for the total elongation was observed.
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Figure 1-9. Stress-strain curves and fracture morphology of 316 L after the Lens process at room
temp [8]
The building direction, which is the acute angle between the longer axis of the
fabricated sample and the horizontal plane had a significant impact on the mechanical
properties of the parts produced by Direct Energy Deposition (DED) process. Guo et
al. (2017) in article [9] detailed the impact of build direction, 0 degree and 90 degree,
on the mechanical properties of the parts produced using direct energy deposition
(DED) process. It was observed that the tensile properties, including the ultimate
tensile strength, the yield strength and the elongation was significantly higher at the
build direction of 0 degree as compared to the build direction of 90 degree. This was
attributed to the fact that at build direction of 0 degree, the loading direction was
parallel to the direction of sliced layer and there was at least one layer in which the
scanning direction was parallel to the direction of tensile loading, as a result the
scanning tracks acted as fibers that reinforced the bulk material.
Figure 1-10. Tensile properties of AISI 316 L stainless steel, fabricated by HP DLD [9]
19
Laser power had a significant impact on the mechanical properties, including the yield
strength and the ultimate tensile strength of additive manufactured products. Zhuqing
Wang et al. (2016) [10], detailed the impact of heat input on the mechanical properties
of 304 L produced by Direct Energy Deposition (DED). An inverse relation was found
between laser power and mechanical properties of parts produced by DED. It has
been observed that, with the increase of laser power, the yield strength and the
ultimate tensile strength decreases. This is because if the laser power is less, then the
grains will be smaller in size and there will be grain boundary strengthening.
In the study by Zietala et. al (2016) [8] ,the author explained the corrosion resistance
of 316 L fabricated by LENS technique. It was found out that the corrosion potential of
additive manufactured 316 L stainless steel was similar to the wrought steel. Corrosion
rate of AM 316 L SS was smaller due to the low current density. The value of
breakdown potential and the re-passivation potential of LENS fabricated 316 L
stainless steel was smaller than the wrought steel but the difference between
breakdown potential and re-passivation potential was greater than that of wrought part.
As a result, the chances of pitting corrosion were quite higher in the parts
manufactured using LENS technology.
Porosity is one of the major defects found in parts made by additive manufacturing
technology. Yusuf, et. al (2017) [11] investigated the porosity of 316 L stainless steel
fabricated by Selective Laser Melting (SLM). Pores effect the mechanical properties
of the manufactured part, in particular the presence of pores tends to reduce the yield
strength and the ultimate tensile strength of the fabricated part. The pores are not
uniformly distributed in the specimen and they exhibit the phenomena of anisotropy.
In study [11], the phenomenon of anisotropy in porosity was confirmed. It was
observed that the pores were mainly concentrated at the boundaries for the samples
along the scan direction. On the other hand, aligned pores were observed along the
build direction as shown in figure.
Figure 1. 11: Porosity distribution along the scan direction [11]
20
Figure 1-12. Porosity distribution along the build direction [11]
Laser power had direct impact on the porosity of additive manufactured components.
Bonaiti et al. (2017) [12] ,the authors detailed that by increasing the laser power, the
effect of porosity was reduced.
In study by Kaynak and Kitay (2018) [13] the author described the impact of cutting
speed on the porosity of additive manufactured 316 L stainless steel. It was found out
that the turning process reduces the problem of porosity which was built in the AM 316
L part. This is because turning process eliminated the partially melted powders on the
surface and subsurface. With the increase in cutting speed, the porosity problem is
reduced. This is because with the increase in cutting speed, the work piece is
subjected to an increase in temperature and stress. This will eventually increase the
fatigue strength of the material.
Figure 1. 13: Porosity observed on the surface and subsurface as built sample (a), (b) Machined sample (Vc=50 m/min); (c) Machined sample (Vc=200 m/min) [13]
1.5 MACHINABILITY OF ADDITIVE MANUFACTURED PRODUCTS
Additive manufacturing has gained importance in manufacturing industry because it
provides high degree of design freedom, reduction in the material wastage and
increased productivity. Poor surface quality of the components, because of the rippling
effect on the molten material, stair case effect due to layer by layer fabrication and
sticking of nonmelted powder particles to the surface is a major issue that remains to
be addressed. Since surface finish had a major impact on the functional performance
of the product, usually the objects manufactured with Additive Manufacturing are
21
subjected to post machining operation in order to obtain the desired surface finish. For
obtaining the desired surface finish of parts fabricated using Additive Manufacturing
technology, proper selection of machining parameters like cutting speed and feed rate
is required.
1.5.1 Effect of cutting speed and feed rate on the cutting force
During machining, cutting speed and feed rate had an impact on the cutting force. With
the increase of cutting speed, cutting force increases for additive manufactured parts.
This could be because as the cutting speed increases, the heat generated at the
deformation zone increases because of adiabatic heating due to high strain rate
deformation and friction between the tool and the workpiece.
Polishetty et al. (2017) [14] detailed the impact of cutting speed and feed rate on cutting
force of wrought and Additive Manufactured Ti-6Al-4V. It was determined that the
cutting force increases with the increase in cutting speed for additive manufactured Ti-
6Al-4V part and it decreases with the increase in cutting speed for the wrought part.
This was attributed to the fact that the wrought parts exhibit the phenomenon of
thermal softening and as a result, the cutting force decreases with the increase in
cutting speed. Porosity and tool wear dominate thermal softening effect, during
machining of additive manufactured Ti-6Al-4V as compared to wrought titanium alloys
and it causes an increase in the cutting force with cutting speed.
During machining, cutting forces are influenced by the feed rate. The cutting forces
usually increases with the increase in feed rate. In study by Polishetty et al. (2017)
[14], It was observed that an increase in the feed rate results in the increase in the
cutting forces for both wrought and Additive manufactured Ti-6Al-4V alloy. This is
because, by increasing the feed rate, the section area of the sheared chip increases,
and as a result large effort is required for the chip removal. Moreover, it was observed
that cutting forces during machining of AM Ti-6Al-4V was observed to be higher than
the wrought part irrespective of the feed rate.
22
Figure 1-14. Cutting forces during machining of wrought and SLM Ti-6Al-4V at cutting speed of 45m/min, 90 m/min and 180 m/min and at feed rate of (a) 0.05 mm/rev, (b) 0.1 mm/rev (c) 0.2mm/rev
and depth of cut 0.5mm [14]
During machining, cutting forces are influenced by the depth of cut. Bonaiti et al. (2017) [12] , the author described the impact of depth of cut on the cutting forces produced during micro milling machining of titanium (Ti-6Al-4V) alloys. It was observed that the cutting forces increases with the increase in the depth of cut.
The building direction, which is the acute angle between the longer axis of the fabricated sample and the horizontal plane had a significant impact on the machineability of additive manufactured alloys. Guo et al. (2017) [9] , detailed the impact of build direction 0 degree and 90 degree on the machinability of additive manufactured 316 L stainless steel alloy. It was observed that, with the increase in cutting speed, the cutting force increases for the both the build direction of 0 degree and 90 degree. Moreover, it was determined that the cutting force was higher for the build direction of 0 degree as compared to 90 degree because of the higher hardness in the build direction of 0 degree as compared to build direction of 90 degree
23
Figure 1-15. Effect of cutting speed on the cutting force of Additive Manufactured 316 L stainless steel
[9]
1.5.2 Effect of cutting speed, feed rate and depth of cut on the surface
roughness
During machining, cutting speed and feed rate had a significant impact on the surface
roughness of the products. It is usually observed that with the increase in cutting speed
the surface roughness decreases. However, an increase in the feed rate results in an
increase in the surface roughness.
Polishetty et al. (2017) [14] detailed the impact of cutting speed and feed rate on the
surface roughness during machining of wrought and Additive Manufactured titanium
Ti-6Al-4V alloys. The surface roughness decreases with the increase in cutting speed
for both Additive Manufactured and wrought titanium alloys. This is due to the fact that
as the cutting speed increases, the material gets softer because of adiabatic and
friction heating at the tool chip interface which reduces the adhered materials on the
tool rake interface. Due to the brittle nature, and high hardness of additive
manufactured Ti-6Al-4V, the surface roughness after machining was found to be less
for additive manufactured titanium Ti-6Al-4V alloy as compared to the wrought part. It
was found out that with the increase in feed rate, the surface roughness increases
during machining of wrought and additive manufactured Ti-6Al-4V alloy. The increase
in surface roughness with the increase in feed rate was due to the tool vibrations and
thermal softening.
24
Figure 1-16. Surface roughness after machining of wrought and SLM Ti-6Al-4V at various cutting
speeds of 45m/min, 90 m/min, 180 m/min at a feed rate of (a) 0.05 mm/rev; (b) 0.1 mm/rev and (c) 0.2 mm/rev and depth of cut 0.5 mm [14]
In study by Kaynak and Kitay (2018) [13] the author described the impact of cutting speed and feed rate on the surface roughness of additive manufactured 316 L stainless steel. It was observed that surface roughness increases with the increase in the feed rate. Surface topography of machined additive manufactured 316 L stainless steel as shown in figure 1.17, indicated the presence of feed marks at all the feed rates. But it was observed that the lower the feed rate, the better is the surface quality.
Figure 1. 17: Surface topography of finish machined SLMed 316 stainless steel (Vc=150 m/min), (a) f=0.08 mm/rev; (b) f= 0.16 mm/rev; (c)= 0.24 mm/rev [13]
25
It was observed that an inverse relation exists between cutting speed and surface
roughness of additive manufactured 316 L stainless steel. It was found out that the
surface roughness was higher at low cutting speed because of the debris reattachment
to the surface. With the increase in cutting speed, sharp reduction in the surface
roughness was observed. This is attributed to the tool wear, which increased at the
nose region of the tool due to increased cutting temperature, and as a result the
increased nose wear will generate a smoother surface. [ Kaynak and Kitay (2018)] [13]
Figure 1. 18: Surface roughness of finished machined SLM 316 L as a function of cutting speed [13]
Mahdavinejad and Saeedy (2011) [15] studied the influence of processing parameters
on the surface quality and tool wear during turning of AISI 304 stainless steel. The
author obtained similar results to account the impact of cutting speed and feed rate on
the surface roughness of the parts. It is observed that as the cutting speed increases,
the surface roughness decreases, while the surface roughness increases with the
increase of feed rate.
Figure 1. 19: Effect of cutting speed and feed rate on the surface roughness of AISI 304 L stainless
steel [15]
Surface roughness is usually effected by many factors including the cutting tool
geometry, feed rate, cutting speed, depth of cut etc. Gokkaya, and Nalbant (2007) in
study [16] investigated the effects of different insert radii of cutting tools, different
depths of cut and different feed rates on the surface quality of the work piece. It was
observed that the surface roughness decreases with the increase in insert radius. The
reason for better surface roughness is attributed to the better roundness of the insert.
26
Figure 1. 20: The average surface roughness values (Ra) obtained by processing of AISI 1030 steel
using three different tools insert radii [16]
The impact of feed rate on the surface roughness was explained by another study by
Gokkaya and Nalbant [16]. It showed similar results as of the other studies and it was
found out that the surface roughness of AISI 1030 steel increases with the increase in
the feed rate.
Figure 1. 21: Average surface roughness obtained by processing of AISI 1030 steel at different feed
rate [16]
Bonaiti et al. (2017) in study [12] detailed the impact of feed rate and depth of cut on
the surface roughness during micro milling machining of additive manufactured Ti-6Al-
4V alloys. It was found out that the surface roughness increases with the increase in
the cutting parameters including the depth of cut and the feed rate. Moreover, it was
found out that machining of the wrought part produces much rougher surface than the
additive manufactured part.
The depth of cut influences the surface roughness of the material. In study by Gokkaya
and Nalbant (2007) [16], it was found that, surface roughness increases with the
27
increase in depth of cut. It is recommended to use low value of depth of cut in order to
obtain better surface finish.
Figure 1. 22: Average surface roughness values obtained by processing AISI 1030 steel at different
depth of cut [16]
1.5.3 Residual Stresses in Additive Manufactured components and effect of
processing parameters on tool wear
Oyelola et al. (2016) in study [17] investigated the machining behavior of additive
manufactured titanium alloy using two different inserts, coated and uncoated inserts.
It was observed that the surface roughness value for coated insert was lower as
compared to the uncoated insert. Surface roughness depends on the processing
parameters and on the tool work combination. Since the resistance of surface layer of
the workpiece to deformation determines the actual contact area between the chip and
tool face, the surface layer resistance was higher for the uncoated tool as compared
to the coated tool because the uncoated tool is made of less abrasive material than
the coated tool.
Figure 1. 23 (a) Regions machined with uncoated insert, (b) Regions machined with coated inserts [17]
28
Capello et al. (1999) in study [18] investigated the influence of turning parameters on
the surface roughness and residual stresses. It was observed that surface roughness
decreases with the increase in nose radius of the inserts.
Özel and Karpat (2005) in study [19] observed that decrease in the feed rate resulted
in better surface roughness but slightly faster tool wear development, and increasing
cutting speed resulted in significant increase in tool wear development but resulted in
better surface roughness. Increase in the work piece hardness resulted in better
surface roughness but higher tool wear.
Nur et al. (2017) [20] the author detailed the impact of processing parameters on the
tool life. Analysis of variance (ANOVA) was carried out in order to analyze the impact
of processing parameters on the tool life. The results of ANOVA analysis reveal that
both cutting speed and feed rate effects tool life. By increasing the cutting speed and
feed rate, the tool life decreases.
The cutting edge of the tool separates chip from the workpiece. With the increase in
tool damage due to wear or fracture the surface roughness and accuracy of the part
decreases. Tool life is usually determined by monitoring the flank wear. In study by
Mahdavinejad and Saeedy (2011) [15], the effect of cutting speed and feed rate on
the flank wear was studied. It was observed that the flank wear decreases with the
increase in cutting speed. This is because at low cutting speed there is lack of efficient
heat removal due to low thermal conductivity of the material and the small area of the
thick chips.
On the other hand, the flank wear increases with the increase in feed rate.
Figure 1. 24: Effect of cutting speed and feed rate on the flank wear [15]
The burr is the accumulation of material along the edges of the workpiece. The
formation of burr depends on the process and the mechanical properties of work
material. Bonaiti et al. [12] , the author analyzed the formation of burr during micro
milling machining of standard and additive manufactured Ti-6Al-4V. It was observed
that little or no burrs were formed during machining of standard titanium. However
29
significant burrs were found when machining additive manufactured titanium alloy. The
burr formation increases with the increase in laser power for AM materials.
The impact of cutting speed and feed rate on chip curl radius was studied in article
[15]. It was determined that by increasing the cutting speed and decreasing the feed
rate, the chip curl radius increases.
Figure 1. 25: chip curl radius at different cutting speeds [15]
Cutting fluid had an impact on the surface quality of the product and the tool life. The
application of cutting fluid during turning of AISI 304 L stainless steel was studied by
Mahdavinejad and Saeedy (2011) [15]. It was observed that the application of cutting
fluid results in longer tool life as compared to the dry machining.
Maruda et al. (2017) [21] studied the tool wear in finish turning of AISI 1045 carbon steel for different cooling conditions: dry cutting, minimum quantity cooling-lubrication (MQCL) and MQCL with phosphate ester-based EP/AW additive and suggested that the tool wear using MQCL + EP/AW method is reduced by about 40% compared to dry cutting and about 25% compared with MQCL.
Tekıner and Yeşılyurt (2004) in study [22] analyzed turning with three different feed rates (0.2, 0.25, 0.3 mm/rev) at each cutting speed, 120, 135, 150, 165, 180 m/min and concluded that with increasing cutting speed, the flank wear decreases. They also studied the effect of the feed rate on flank wear value, flank wear is decreasing while feed rate is rising from 0.2 to 0.25 mm/rev; and then it is starting to increase when it is rising 0.3 mm/rev.
Figure 1. 26: Effect of cutting speed and feed rate on the flank wear [22]
30
Choudhury and Srinivas (2004) [23] studied that the flank wear increases with an increase in speed. However, within the range of 90–110 rpm, the flank wear increases rapidly, which is probably because of the built-up-edge formation.
Guo et al. (2017) [9], the author described the impact of build direction 0 degree and 90 degree on the tool life. By increasing the cutting speed, there is high strain rate in the primary deformation zone and higher degree of strain hardening during chip formation. The higher heat generation rate reduced the wear resistance of the tool which results in increased tool wear. The tool wear was higher in build direction of 0 degree as compared to 90 degree.
Figure 1. 27: Effect of cutting speed on the tool wear of AM 316 L stainless steel [9]
Analysis of variance (ANOVA) was carried out by Nur et al. [20] to analyze the impact
of processing parameters on the tool life. The results of ANOVA analysis reveal that
both cutting speed and feed rate effects tool life. By increasing the cutting speed and
feed rate, the tool life decreases.
Figure 1. 28: Response surface graphs of (a) contours and (b) 3D surface for tool life [20] In order to obtain sustainable production during turning operation, the impact of
processing parameter on the power consumption is studied by Nur et al. in [20]. It was
determined that the power consumption increases with the increase in cutting speed
and feed rate. This is because with the increase in spindle speed, high power is
31
needed by the motor to rotate the spindle, and when the cutting action takes place,
the motor consumes even more power to maintain the spindle speed
Figure 1. 29: Response surface graphs of (a) contours and (b) 3D surface for Power consumption [20]
1.5.4 Microhardness of Additive Manufactured 316 L stainless steel
The micro hardness of additive manufactured parts is significantly different from the
wrought part made of same material. Zietala et al (2016) in study [8] and Yusuf et al.
(2017) in their study [11] described the micro hardness of additive manufactured 316
L stainless steel fabricated using LENS technology. It was observed that the micro
hardness of additive manufactured 316 l stainless steel was higher than wrought steel.
This is because of the fine grain microstructure, localized melting of the powder layer
and rapid heating /cooling. Moreover, the higher concentration of dislocation density
of austenitic cells causes the slip motion along the grain boundaries much difficult, and
as a result it increases the strength and resistance to deformation.
Guo et al. (2017) [9] detailed the impact of build direction, 0 degree and 90 degree on
the micro hardness of additive manufactured DED 316 L stainless steel. The
microhardness at build direction of 0 degree was higher as compared to that at build
direction of 90 degree. The higher hardness was because of the layer wise build
approach and the localized melting of the powder which results in non-homogeneous
and anisotropic dendrite grain microstructure
Surface hardness of metallic materials influences the response capability of
components when it is subjected to different environmental and contact conditions.
For the wrought materials, with the increase in cutting speed, the microhardness
reduces. This is because with the increase in cutting speed, the temperature increases
which leads to thermal softening and as a result reduction in microhardness.
Kaynak and Kitay (2018) in study [13] detailed the variation in the microhardness of
additive manufactured 316 L stainless steel with the variation in the cutting speed and
feed rate.
It was observed that with the increase in cutting speed, the microhardness increases
for the additive manufactured 316 L stainless steel. The increase in hardness is
because the machining process induces stress and as a result it increases dislocation
32
density on the surface and subsurface of machined SLM 316 stainless steel part.
Moreover, at high cutting speed, deformation occurs with high strain rate which leads
to larger strain hardening and consequently increases the microhardness.
Figure 1. 30: Micro hardness of finished machined and as built SLMed 316 L SS as a function of
cutting speed (feed= 0.08 mm/rev) [13]
It was observed that, a direct relation exists between feed rate and micro hardness of
additive manufactured 316 L stainless steel. The micro hardness value of 316 L
stainless steel increases with the increase in feed rate.
Figure 1. 31: Micro hardness of finished machined and as built SLMed 316 L SS as a function of feed
rate (Vc= 150 m/min) [13]
Oyelola et al. (2016) in study [17] investigated the hardness of additive manufactured
titanium alloy using two different inserts, coated and uncoated inserts. It was observed
that the hardness value of additive manufactured titanium alloy after machining
increase for both coated and uncoated inserts. The hardness value for both inserts,
coated and uncoated, were like each other.
Kamariah et al. (2017) in their study [24] detailed the impact of heat treatment on the
micro hardness of additive manufactured 316 L stainless steel. The study revealed
that heat treatment of additive manufactured 316 L stainless steel results in the
decrease of its microhardness as compared to the microhardness of the built in 316 L
stainless steel. It was observed that the micro hardness decreases with the increase
33
in the heat treatment temperature. Moreover, he variation of micro hardness value for
different building orientation reveals anisotropy in the microhardness of additive
manufactured 316 L stainless steel.
Additive manufacturing processes induces residual stresses due to rapid cooling and
solidification of the material. Capello et al. (1999) [18] proposed that during machining,
tensile residual stresses are caused by thermal effects, while compressive residual
stresses are caused by the action of the cutting tool. It was observed that the region
in front of the tool experiences a rise in compressive plastic deformation while tensile
plastic deformation is observed for the regions just after the tool.
Oyelola et al. (2016) in study [17] investigated the residual stresses induced during
machining of additive manufactured titanium alloy using two different inserts, coated
and uncoated inserts. It was observed that the compressive residual stresses
produced by coated tools were higher as compared to the uncoated tools.
Capello et al. (1999) in study [18] investigated the influence of turning parameters on
the surface roughness and residual stresses. It was observed that the residual
stresses were mainly influenced by feed rate and nose radius. The residual stresses
increase, with the increase in feed rate and the nose radius.
Figure 1-32. Effect of feed rate and nose radius on the residual stresses [18]
34
2 AIM OF THE WORK
Direct Energy Deposition (DED), is a type of additive manufacturing process that is
used to fabricate complex three-dimensional (3D) metallic and functional objects, by
the layer-wise addition of material based on a predefined computer aided design
(CAD) data. Additive manufacturing processes provides many advantages as
compared to conventional manufacturing techniques; one of the major drawbacks of
this technology is the poor surface quality. Therefore, in order to improve the surface
characteristics, hybrid manufacturing is adopted in which components fabricated by
additive manufacturing are subjected to finish machining operation. Finish machining
processes includes either turning or milling operations, which is selected based on the
geometry of the additive manufactured parts.
Poor surface quality of the components fabricated by additive manufacturing
technology because of the rippling effect on the molten material and the sticking of
non-melted powder particles to the surface is a major issue that remains to be
addressed. Since the functionality of additive manufactured parts highly depend on
the geometric and dimensional accuracy, therefore the surface characteristics or
approaches to enhance the surface characteristics of the additive manufactured
components must be considered. Although a lot of work had been done in the field of
additive manufacturing of AISI 316 L stainless steel components, but the study of
complete process chain from fabrication, heat treatment to finish machining operation
yet remain to be investigated. Therefore, the main goal of this study is to develop a
complete process chain, in which the components fabricated by additive
manufacturing process are subjected to post processing operations of heat treatment
and finish turning, that helps in improving the surface characteristics of components
fabricated by additive manufacturing.In my study, a complete process chain has been
developed starting from the printing of additive manufactured DED 316 L stainless
steel tubes to heat treatment and afterwards finish turning operation, both external and
internal turning operation, was carried out. The process chain is detailed in figure 2.1:
Figure 2-1. Process Chain on DED 316 L stainless steel tube
In order to determine the effect of post processing operations i.e. heat treatment and
finish turning on the dimensional and surface characteristics of additive manufactured
DED 316 L stainless steel tubes, a qualitative analysis was carried out at each step:
Fabrication
of DED 316
L stainless
steel tubes
Heat
Treatment
of DED 316
L tubes
Substrate
removal by wire
EDM of DED 316
L tubes
Machining
(external/internal)
turning operation
35
right after deposition, then heat treatment and after that finish machining on each of
the DED 316L tube. For each step the qualitative analysis involves the measurement
of the dimensional characteristics of the tubes in terms of the external and internal
diameter, external and internal roundness, external and internal cylindricity; the
measurement of roughness of DED 316 L tubes and the determination of the
mechanical properties in terms of microhardness of additive manufactured DED 316
L stainless steel cylindrical tubes.
Figure 2-2. Operations carried out at Each step
A design of analysis experiment was then conducted to analyze the impact of heat
treatment, batch order, cylinder height and blocking factor day on the dimensional
characteristics of additive manufactured DED 316 L stainless steel cylindrical tubes.
A Multiway ANOVA analysis was conducted to determine the impact of heat treatment,
position and external/internal surface on the surface roughness and microhardness of
additive manufactured DED 316 L stainless steel cylindrical tubes. A 2k factorial
design of analysis experiment was carried out in order to determine the impact of
machining parameters i.e. cutting speed and feed rate on the surface roughness and
microhardness of machined DED 316 L stainless steel tubes.
Fabrication:
- Determination
of dimensional
characteristics
- Roughness
measurement
- Hardness
measurement
Heat Treatment:
- Determination
of dimensional
characteristics
- Roughness
measurement
- Hardness
measurement
Substrate
removal:
- Determination
of dimensional
characteristics
Machining:
- Determination
of dimensional
characteristics
- Roughness
measurement
- Hardness
measurement
36
3 MATERIAL AND METHODOLOGY
3.1 PROCESS CHAIN
15 additives manufactured DED 316 L stainless steel cylindrical tubes were produced
using Direct Metal Deposition technology. The dimensional characteristics of the
tubes including external/internal diameter, external/ internal Cylindricity and external/
internal roughness were measured using Coordinate Measuring Machine System
(CMMS). In order to analyze the impact of position, orientation, external/ internal
surface of the tube on the surface roughness of additive manufactured DED 316 L
stainless steel tubes, the surface roughness, both external and internal roughness,
were measured at 3 different positions (close to the substrate, at the middle and close
to the edge) and along the 4 orientations of the tubes by using a mechanical
profilometer. 3 samples of DED 316 L tubes were used to measure the microhardness
of the as built DED 316 L stainless steel.
Figure 3-1. Representing the different positions of specimen
12 DED 316 L stainless steel tubes and 3 half samples were then subjected to Heat
Treatment process by using a vertical furnace under vacuum at TENOVA. After
thermal treatment, the dimensional characteristics and the surface roughness of the
12 samples were again measured using Coordinate Measuring Machine system
(CMMS) and mechanical profilometer respectively in order to determine the impact of
heat treatment on the dimensional characteristic and the surface roughness of additive
manufactured DED 316 L stainless steel tubes. To analyze the impact of heat
treatment on the microhardness, 3 half samples of additive manufactured DED 316 L
stainless steel tubes after heat treatment, were then used to measure the
microhardness of DED 316 L tubes using Vickers hardness machine.
After Heat Treatment, Wire EDM process was used to remove the substrate from 12
samples of additive manufactured DED 316 L stainless steel tubes. After the substrate
removal, the dimensional characteristics of the tubes were measured again using
Coordinate Measuring Machine System (CMMS) to analyze whether wire EDM
process influences the Cylindricity and roundness profile of the DED 316 L stainless
steel tubes due to the generation of residual stresses.
37
Since the surface quality of additive manufactured DED 316 L stainless steel
cylindrical tubes is usually less than the wrought part, therefore in order to improve the
surface quality of the tubes, the DED 316 L stainless steel tubes were then subjected
to external and internal turning operations. The machining parameters, including the
cutting speed and feed rate was varied while the depth of cut was kept constant. 2
levels of cutting speed and 2 levels of feed rate were chosen. Each experimental
condition was replicated 3 times. After machining, the geometric analysis of the 12
machined DED 316 L stainless steel tubes was carried out with the help of Coordinate
Measuring Machine System (CMMS). In order to analyze the impact of machining
parameters i.e. cutting speed and feed rate on the surface roughness and
microhardness of additive manufactured DED 316 L stainless steel tubes, the surface
roughness and microhardness measurements of 12 machined DED 316 L stainless
steel tubes was carried out by using a mechanical profilometer and Vickers hardness
machine. The Process chain is explained in figure.
Figure 3-2. Flow Chart of Study
Fabrication of 15 316 L stainless steel cylindrical tubes using DED
Dimensional Measurement of 15 as-built tubes using CMMS treatment
Measurement of the External/Internal roughness of 15 DED 316 L tubes using Mechanical Profilometer
Hardness measurement of the 3 as-built 316 L tubes
Heat treatment of 3 half samples and 12 DED 316 L cylindrical tubes
Dimensional Measurement of the 12 parts using CMMS after heat treatment
External & Internal roughness of 12 DED 316 L tubes using mechanical profilometer after heat treatment
Hardness measurement of 3 half samples of DED 316 L after heat treatment
Substrate removal of 12 316 L tubes using wire EDM
Dimensional Measurement of 12 tubes using CMMS after substrate removal
Machining (External/Internal Turning) operation on the 12 tubes
Dimensional Measurement of 12 tubes using CMMS after turning
External/Internal Roughness measurement of 12 316 L tubes after turning
Hardness measurement of 12 316 L tubes after machining
38
The powder material used for printing the DED 316 L stainless steel tubes, the Direct
Metal Deposition (DMD) parameters employed for the fabrication of the 316 L stainless
steel tubes, the parameters for heat treatment and substrate removal using Wire EDM
and the turning operation carried out on additive manufactured 316 L stainless steel
tubes are detailed below.
The instruments used for quality evaluation of additive manufactured DED 316 L
stainless steel tubes, including the measurement of dimensional characteristics of the
tubes using Coordinate Measuring Machine System (CMMS), the roughness
measurement by using mechanical profilometer and the measurement of hardness
using Vickers hardness machine are also detailed below:
MATERIAL USED
3.2 EMPLOYED POWDER
15 316 L stainless steel cylindrical tubes having a diameter of 35 mm and a length of
50 mm were built on an unheated substrate plate of the same material using Direct
metal deposition technology.
The 316 L stainless steel powder size distribution was between 45 µm and 90 µm. The
chemical composition of material is detailed in table [1].
Component Fe Cr Ni Mo Mn Si P C S
Weight % Bal. 16.5-18.5
10.0-13.0
2.0-2.5
<2.0 <1.0 <0.045 <0.030 <0.030
Table 3-1. Chemical Analysis
METHODOLOGY
3.3 EMPLOYED SET-UP
The additive manufactured 316 L stainless steel cylindrical tubes were fabricated using
Direct Energy Deposition technology. The tubes were then subjected to heat treatment
at TENOVA. In order to remove substrate from the DED 316 L stainless steel tubes, a
wire EDM process was carried out. In order to improve the surface characteristics of
additive manufactured DED 316 L stainless steel cylindrical tubes, finish machining,
both external and internal turning operations were conducted. The processes are
detailed as:
3.3.1 Manufacturing of 316 L stainless steel cylindrical tube using ADDITUBE
CELLS
15 316 L stainless steel cylindrical tubes were built in 3 different days, with 5 tubes per
batch, using Direct Metal Deposition technology. The used Direct energy deposition
system is characterized by 3 kW Ytterbium continuous wave (CW) fiber optic laser
source with a Gaussian beam diameter, Kuka laser Deposition head with a variable
39
collimation. The collimation lens is characterized by a length of 129 mm and the focal
lens by a length of 200 mm. The process uses argon both as shielding and carrier gas.
Figure 3-3. Direct Metal Deposition to fabricate 316 L stainless steel cylindrical tubes
The 316 L stainless steel powder size distribution was between 45 µm and 90 µm. The
316 L stainless steel cylindrical tubes had a diameter of 35 mm, length of 50 mm and
were built on an unheated substrate plate of the same material within the DMD system.
The laser parameters used for producing DED 316 L stainless steel cylindrical tubes
are detailed in table 3.2.
Laser Source Ytterbium 3000 (YLR 3000)
Mode Continuous Wave
Wave length 1070 nm
Laser Power 3000 W
Focal spot diameter 0.774 mm
𝑴𝟐 47.2
Table 3-2. Laser Processing Parameters
In the Direct Metal deposition process, 316 L stainless steel powders with a dimension
ranging from 45-90 µm were used. A 5 mm thick stainless-steel plate was used as a
substrate. The substrate was attached to the rotary table of cell. The table is made to
rotate around its axis. The position of the laser head is fixed and is made to move only
in the vertical direction using a robot in order to adjust the height. The powder is fed
using a 3-way nozzle from “Fraunhofer ILT” into the laser head. The powder was
delivered by Argon as carrier gas and the melt pool was locally shielded by Argon to
prevent oxidation of the resulting deposits. The tubes produced were allowed to cool
under this condition. The layer thickness was assumed equal to the layer of a single
track (0.2mm) and the robot was moved along the z axis of 0.2 mm for each layer. The
standoff distance were set at 12 mm respectively. The processing parameters used
for Direct Metal deposition are detailed in table 3.3:
40
Laser power 370 W
Traverse speed 22 mm/sec
Spot diameter on substrate 1.2 mm
Layer thickness 0.2 mm
Stand off distance 12 mm
Powder mass flow rate 9.2 g/min
Shielding gas (Argon) 25 l/min
Carrier gas for powder 7.2 l/min Table 3-3. Direct Metal Deposition Process Parameters
3.3.2 Heat Treatment Methodology
Heat Treatment was performed using a vertical furnace under vacuum. The DED 316
L stainless steel cylindrical tubes were first subjected to a temperature rise that goes
from 0℃ to 550℃ in 3 hours. This temperature of 550℃ was then maintained for 6
hours. The tubes were then allowed to cool down slowly to room temperature with air
cooling.
Steps Heat Treatment cycle
1: Heating 0℃ to 550 ℃ in 3 hours
2: Temperature Maintained 550℃ for 6 hours
3: Cooling Air Cooling
Table 3. 4: Heat Treatment applied to the DED 316 L stainless steel cylindrical tubes
3.3.3 Wire EDM for Substrate Removal
In order to remove substrate from DED 316 L stainless steel cylindrical tubes, wire
EDM is used. The process uses Brass wire having a diameter of 0.20 mm. The wire
used and processing parameters of EDM process are detailed in table 3.5.
Wire Used Diameter
(mm) Height Roughness
Ra, (µm)
Speed Offset (µm)
AC Brass 900
0.20 5 2.70 16.50 121.0
Table 3-5. Wire EDM Parameters
41
3.3.4 Turning operation
The finish machining operation on additive manufactured DED 316 L stainless steel
cylindrical tubes was conducted on a manual turning machine, which has a maximum
spindle speed of 1100 rpm as shown in figure 3.4.
Figure 3-4. Lathe Machine
The tools used for external and internal turning operations are detailed in table 3.6:
Process Tool Code Tool used Recommended Parameters by sandwich
External Turning
VCET 11 03 02-UM 1115
Cutting speed vc:245 m/min (245-245) Feed rate fn:0.03mm/r (0.02-0.08) Depth of cut ap: 0.5 mm (0.2-4)
Internal Turning
DCGT 07 02 02-UM 1115
Cutting speed vc:240 m/min (240-220) Feed rate fn:0.03mm/r (0.02-0.16) Depth of cut ap: 0.5 mm (0.1-1.5)
Table 3-6. Tools used for External and internal turning
During turning operation, the parts is clamped into a three bites chuck, which creates
clamping pressure and as a result, induces deformation in the part. A mandrel covered
with an adhesive was inserted at the bottom surface of the cylindrical tubes in order to
avoid the deflection of the tubes.
During machining, the problem of run out arises, since the roundness of additive
manufactured DED 316 L stainless steel cylindrical tubes vary from the bottom layer
to the top layer. The run out was measured with the help of a simple height gauge as
shown in figure 3.5. The cylindrical tube, clamped in spindle, is then rotated around
the datum axis and the variation was measured using the height gauge which was
42
held perpendicular to the cylindrical tube. The cylindrical tube was then adjusted
around the axis, so that the height gauge does not vary by more than the run-out
tolerance.
Figure 3-5. Height gauge to avoid run out
The tool is then clamped tightly into the tool holder. The angle of the tool holder is
adjusted so that the tool is approximately perpendicular to the DED 316 L stainless
steel cylindrical tubes. A live center is installed into the tail stock to align the tool as
shown in Figure 3.6.
Figure 3-6. Tool Alignment
Power is then turned on and the spindle is made to rotate in the clockwise direction.
An initial contact was made between the tool and workpiece in order to set the
reference position for the depth of cut. The machining parameters were then set and
the lead screw lever is rotated in clockwise direction so that the lead screw gets
engaged with the gear train and the carriage moves. The tool moves parallel to the
axis of DED 316 L stainless steel cylindrical tube.
The machining parameters were selected based on the results of preliminary test and
considering the recommendations from Sandvik. Cutting speeds were selected as
250 rpm (27m/min) and 500 rpm (54m/min). In machining tests, the depth of cut (ap)
was kept constant to be 0.25mm and feed rate (fn) of 0.07 mm/rev and 0.14 mm/rev
respectively. Each experimental condition was replicated three times.
43
Process Cutting speed (vc) (m/min)
Feed Rate (fn) (mm/rev)
Depth of cut (ap) (mm)
External Turning 27 m/min; 54 m/min 0.07 mm/rev;0.14 mm/rev 0.25 mm
Internal Turning 27 m/min; 54 m/min 0.07 mm/rev;0.14 mm/rev 0.25 mm
Table 3-7. Parameters used for turning operation
The finish machining operations were performed under dry machining conditions
without any lubricant and coolant liquid as depicted in the figure 3.7. In order to have
homogenous condition, new insert was used for each specimen. External and internal
turning operation was replicated for all the 12 DED 316 L stainless steel cylindrical
tubes.
(a) (b)
Figure 3-7. (a) External Turning (b) Internal Turning
3.4 Instruments for evaluation of parts quality
A qualitative analysis was carried out at each step: right after deposition, after heat
treatment and after finish machining on each of the DED 316L tube. For each step the
qualitative analysis involves the measurement of the dimensional characteristics of the
tubes in terms of the external and internal diameter, external and internal roundness,
external and internal cylindricity; the measurement of roughness of DED 316 L tubes
and the determination of the mechanical properties in terms of microhardness of
additive manufactured DED 316 L stainless steel cylindrical tubes. The dimensional
characteristics and surface roughness of DED 316 L tubes were acquired using
Coordinate Measuring Machine System (CMMS) and mechanical profilometer
respectively while the hardness measurements were obtained using Vickers hardness
testing machine.
3.4.1 Measurement of the parts
The parts were measured on a Zeiss Prismo VAST HTG Coordinate Measurement
Machine (CMM). The machine is characterized by a 𝐸0,𝑀𝑃𝐸 = 2 +𝐿
3⋅105 μm, where 𝐿 is
the length of the reference standard, according to ISO 10360-2. The parts were fixed
to the CMM table by means of a chuck. Thermocouples were connected to the part,
allowing the compensation of the thermal expansion. The part was measured by
means of an 8mm ruby probe. The diameter was chosen in order to reduce the
44
influence of the serious asperities of the surface. The part was aligned by setting the
z axis perpendicular to the base plate, and the origin was on the base plate (z
coordinate), and at the center of the circumference measured at 5 mm from the base
plate (x and y coordinates). As the part is cylindrical, the y axis was simply set
approximately parallel to the CMM y axis. 15 evenly spaced circumferences were
measured by scanning probing both inside and outside the tube. The bottom
circumference was located at 5 mm from the base plate, and the top circumference at
1 mm from the free end of the tube. The scanning speed was equal to 8 mm/s. The
sampling spacing was equal to 0.1 mm. For each circumference, the following
characteristics were measured:
• Least squares diameter
• X coordinate of the center
• Y coordinate of the center
• Roundness deviation
Then, the internal and external circumferences were collected to form an inner and an
outer cylinder. For each cylinder, the following characteristics were measured:
• Least squares diameter
• Cylindricity
All measurements were repeated four time for each sample: right after deposition, after
thermal treatment, after removal from the base plate, and after turning
Figure 3-8. CMMS Measurement
3.4.2 Roughness Measurement
Additive manufacturing techniques are widely used to manufacture metallic
components. One of the major drawbacks of this technique is the surface quality,
which is usually beyond the acceptable range. Therefore, hybrid manufacturing,
including additive manufacturing and finish machining is becoming more and more
popular in the industry.
From the literature, we come to know that surface roughness of additive manufactured
parts usually varies from the bottom layer to the top layer. In order to analyze the effect
45
of position on the surface roughness (Ra) of additive manufactured DED 316 L
cylindrical tubes, 3 positions namely (M1: close to the substrate, M2: at the middle,
M3: at the top layer) were marked on the DED 316 L cylindrical tubes as shown in
figure 3.9. These 3 positions were marked along 4 orientations of all the 15 DED 316
L cylindrical tubes.
Figure 3-9. Figure representing the different position of the specimen
The specimens were then clamped in the metallic vise. A leveler was used in order to
maintain the horizontal position of the specimen as shown in figure 3.10.
(a) (b)
Figure 3-10. (a): Leveler for balancing position; (b): Ra internal
The surface roughness values (Ra), both external and internal, were measured at
three different positions (M1: close to the substrate, M2: at the middle, M3: close to
the top layer) by using a mechanical profilometer, with a cut off length equal to 5.6 µm
as shown in figure 3.11. The stylus is usually attached to a piezoelectric crystal or with
a small magnet which moves inside a coil and induces a voltage in the coil which is
proportional to the magnitude of substrate variation. When the stylus changes its
position on the specimen, it causes a change in the mutual inductance in the coils,
modulating a high frequency carrier signal in proportional to the displacement of the
stylus. The carrier signal is then amplified and demodulated to generate a signal which
represents the surface profile that is used to evaluate the surface roughness.
46
Figure 3-11. Mechanical profilometer
The specimen was then rotated and is clamped in the 2nd, 3rd and 4th orientation and
the roughness values were obtained at the 3 positions (M1, M2, M3).The average
value of surface roughness (Ra) was then computed for each position (M1, M2, M3)
by using the observations obtained from all the 4 orientations of a specimen at
respective positions (M1, M2, M3). The measurement of surface roughness (RA) was
repeated three times for each specimen:
• Surface Roughness (RA) of DED 316 L after deposition
• Surface Roughness (RA) of DED 316 L after heat treatment
• Surface Roughness (RA) of DED 316 L after machining
(a) (b) (c)
Figure 3-12. (a) Ra as built (b) Ra after HT (C) Ra after machining The results for surface roughness (Ra) values before and after heat treatment for both
external and internal surfaces were reported in the appendix table.
In order to analyze the effect of position, orientation, batch order, day, External/Internal
part and heat treatment on the surface roughness (Ra), a Design of Analysis
Experiment was conducted for both external and internal roughness. In the Design of
Experiments (DOE), three levels of the factor position (M1: close to the substrate, M2:
at the middle, M3: close to the top surface), four levels for batch order (1, 2, 3, 4), three
47
levels for day (1, 2, 3),four levels for orientation (1,2,3,4), two levels of factor
External/internal (0:External; 1:Internal) and two levels for the factor heat treatment (0:
before Heat treatment, 1: After Heat treatment) were used. Batch order and day were
considered as blocking factor in the analysis. Surface roughness (Ra), for both
external and internal surfaces were used as response variable.
After machining, the surface roughness (Ra) was measured at two different positions
(M2: in the middle, M3: close to the top layer), for both external and internal surfaces,
by using a mechanical profilometer with a cut off length equal to 5.6 µm. The
roughness values were obtained along all the four orientations of the specimen. The
mean value of surface roughness was then computed.
A 2k factorial Design of Experiments (DOE) methodology was used to analyze the
impact of cutting speed and feed rate on the surface roughness of additive
manufactured DED 316 L stainless steel cylindrical tubes. 2 levels of cutting speed
(spindle speed: 250 rpm, 500 rpm), 2 levels of feed rate (0.07 mm/rev and 0.14
mm/rev) were employed. The depth of cut was kept constant to be 0.25 mm. Each
experimental condition was replicated 3 times. The experiments were performed in a
completely randomized manner. In order to avoid the effect of tool wear on machining,
a new tool was used for each specimen.
3.4.3 Measurement of Hardness
Keeping in view the literature, we come to know that the hardness of additive
manufacturing parts tends to vary from top to the bottom and middle layer of the part
because the cooling rate of the melt pool and velocity of solidification is slower in the
middle region as compared to the bottom layer. To analyze the impact of heat
treatment, variation of micro hardness along the layers of additive manufactured DED
316 L stainless steel tubes and to determine the effect of machining parameter on the
micro hardness of DED 316 L stainless steel cylindrical tubes, the hardness test is
performed on Vickers Hardness machine by following the international standards.
• In order to measure the micro hardness of DED 316 L stainless steel cylindrical
tubes, the tubes were first cut into 2 halves.
• Since when doing Vickers hardness test, it is usually necessary to prepare the
surface of specimen that is to be tested, the additive manufactured DED 316 L
cylindrical tubes were first polished using silicon carbide (SIC) grinding paper
with a grit size of 120 µm ,180 µm ,320 µm ,600µm,800 µm, 1200 µm and 2400
µm respectively in both horizontal and vertical directions. The details are
reported in Table 3.8:
48
Step Medium Lubricant Speed (rpm)
Direction sample holder
Time (min)
Polishing SiC, P120 Water 150 Clockwise 1.0
Polishing SiC, P180 Water 150 Clockwise 1.0
Polishing SiC, P320 Water 150 Clockwise 1.0
Polishing SiC, P600 Water 150 Clockwise 1.0
Polishing SiC, P800 Water 150 Clockwise 1.0
Polishing SiC, P1200 Water 150 Clockwise 1.0
Polishing SiC, P2400 water 150 clockwise 1.0
Table 3-8. Parameters for Polishing of DED 316 L cylindrical tubes
The polished specimens were then clamped on the working platform of Vickers
hardness machine in order to avoid the movement of the specimen and to keep the
samples horizontally on a parallel plane.
Figure 3-13. Sample Adjustment
• The instrument was first calibrated by rotating the lever, used for changing the
optical path, until the two lines overlap each other.
• A highly polished, pointed, square based pyramidal diamond shape indenter
with a face angle of 136° was used for indentation.
• A load of 500 grams and a dwell time of 15 seconds was selected for
indentation.
• First, the focal position was set in order to obtain the surface image of the DED
316 L cylindrical tubes.
• After adjusting the focal position, the indentation load of 500 grams using
diamond indenter was applied on the specimen for 15 sec.
• After the dwell time of 15 sec, a diamond shape indenter can be seen on the
surface by using an eyepiece. Both diameters of the indenter were measured,
and their mean value was used for calculation of Vickers Hardness.
• 3 observations each at the top, middle and the bottom layers of DED 316 L
stainless steel cylindrical tubes were acquired with an indentation spacing,
equal to 3 times the length of diagonal of the impression.
• The process was repeated for all the specimens before and after heat
treatment.
• The mean value of hardness was then calculated at the top, middle and the
bottom layers of each specimen and afterwards, a Design of Analysis
49
experiment was performed in order to determine the influence of position and
heat treatment on the micro hardness of additive manufactured DED 316 L
cylindrical tubes. Three levels of position (1: close to the substrate, 2: at the
middle, 3: top layer) and two levels of the factor Heat Treatment (0: Before Heat
Treatment, 1: After Heat Treatment) were used in the analysis.
• In order to determine the impact of cutting speed and feed rate on the micro
hardness of DED 316 L cylindrical tubes, three observations of hardness were
obtained for each machined specimen by applying an indentation load of 500
grams and a dwell time of 15 seconds. The average value for hardness was
calculated and Design of analysis experiment was performed in order to
determine the impact of machining parameters on the micro hardness of
additive manufactured DED 316 L stainless steel cylindrical tubes. Two levels
of cutting speed (27m/min and 54 m/min) and two levels of feed rate (0.07
mm/rev and 0.14 mm/rev) were used. Each experimental condition was
replicated three times.
Figure 3-14. Vickers Hardness Measurement
50
4 PRELIMINARY TESTS
In order to select the parameters for machining operation, some preliminary tests were
performed on the additive manufactured DED 316 L cylindrical tubes. The focus was
on the surface quality of DED 316 L stainless steel cylindrical tubes, subjected to
different machining conditions.
The working parameters were selected by carefully analyzing the state of the art,
considering the recommendations from Sandvik experts and by consulting laboratory
technician of Politecnico di Milano to better understand how the machining
parameters will influence the surface characteristics of additive manufactured DED
316 L stainless steel cylindrical tubes. Six samples of additive manufactured DED 316
L cylindrical tubes were subjected to both, external turning and internal turning, by
applying different machining conditions. The working parameters tested for different
specimens are reported in table 4.1:
Specimen Cutting speed (rpm)
Feed rate (mm/rev)
Depth of cut (mm)
1 250 0.07 0.25
2 250 0.14 0.25
3 350 0.07 0.5
4 350 0.14 0.5
5 500 0.07 0.25
6 500 0.14 0.5
Table 4-1. Machining parameters used for testing
4.1 RESULTS OF PRELIMINARY TESTS
The roughness values (Ra), for both external surface and internal surface, was
measured for all the specimens by using a profilometer with a cut off length of 5.6 µm.
The roughness values (Ra), external and internal, before and after machining
operation are reported in table 4.2, 4.2 and figures 4.1 and 4.2 respectively.
Specimen Cutting speed (rpm)
Feed rate (mm/rev)
External Roughness (Ra)before
turning (µm)
External roughness (Ra) after turning
(µm)
1 250 0.07 10.5 1.10
2 250 0.14 10.8 3.61
3 350 0.07 12.1 1.40
4 350 0.14 11.3 3.73
5 500 0.07 10.2 1.50
6 500 0.14 9.8 3.94
Table 4-2. External Roughness (Ra) before and after machining
51
Graphical Representation
Figure 4-1. External roughness after machining of DED 316 L at various spindle speed (250 rpm, 350 rpm, 500 rpm) and feed rate (0.07 mm/rev; 0.14 mm/rev)
Based on the results of table 4.2, it was found out that machining process had a
significant impact on the surface roughness of additive manufactured DED 316 L
stainless steel cylindrical tubes. Moreover, it was found out that with the increase in
cutting speed and feed rate, internal roughness (Ra) was increasing for additive
manufactured DED 316 L cylindrical tubes.
Specimen Cutting speed (rpm)
Feed rate (mm/rev)
Internal Roughness (Ra)before
turning (µm)
Internal roughness (Ra) after turning
(µm)
1 250 0.07 12.1 1.42
2 250 0.14 13.4 3.0
3 350 0.07 11.8 1.7
4 350 0.14 12.5 3.2
5 500 0.07 11.6 2.6
6 500 0.14 11.9 3.9
Table 4-3. Internal Roughness (Ra) before and after machining
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
250 350 500
Surf
ace
Ro
ugh
nes
s (µ
m)
Cutting speed (rpm)
Effect of cutting speed and feed rate on external roughness (Ra)
feed rate (0.07 mm/rev) feed rate (0.14 mm/rev)
52
Graphical Representation
Figure 4-2. Internal Roughness after machining of DED 316 L at various spindle speed (250 rpm, 350
rpm, 500 rpm) and feed rate (0.07mm/rev, 0.14 mm/rev)
Based on the results of table 4.3, it was found out that machining process had
significantly improved the internal roughness of additive manufactured DED 316 L
stainless steel cylindrical tubes. Moreover, it was found out that with the increase in
cutting speed and feed rate, internal roughness (Ra) was increasing for additive
manufactured DED 316 L cylindrical tubes.
4.2 SELECTED PARAMETERS
Sandvik experts have recommended to use depth of cut (ap) of 0.5 mm. Since the
thickness of specimens is around 1 mm, therefore we decided to use depth of cut (ap)
of 0.25 mm rather than 0.5 mm. The cutting speed (vc) recommended from Sandvik
for external and internal turning were (245 m/min and 240 m/min) respectively. The
feed rate (fn) recommendations from Sandvik for external and internal turning were
(0.02-0.08 mm/rev) and (0.02-0.16 mm/rev) respectively.
Since, in my study I have to analyze the influence of machining parameters on the
surface roughness (Ra) and micro hardness of additive manufactured DED 316 L
cylindrical tubes, with the help of “Design and Analysis of Experiments”. I decided
to use 2 levels of cutting speed and 2 levels of feed rate for both external and internal
turning operations. Therefore, by analyzing the results of surface roughness (Ra) for
the preliminary tests and by considering the recommendations from Sandvik experts,
the machining parameters which I selected for my case study are reported in table 4.4.
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
250 350 500
Inte
rnal
Ro
ugh
nes
s (µ
m)
Cutting Speed (rpm)
Effect of cutting speed and feed rate on Internal Roughness (Ra)
feed rate (0.07 mm/rev) feed rate (0.14 mm/rev)
53
Cutting speed (rpm)
Feed rate (mm/rev)
Depth of cut (mm)
250 0.07 0.25
250 0.14 0.25
500 0.07 0.25
500 0.14 0.25
Table 4-4. Machining parameters selected
54
5 RESULTS
5.1 RESULTS OF COORDINATE MEAUSRING MACHINE SYSTEM (CMMS)
5.1.1 Effect of Cylinder Height and Heat Treatment on External Roundness of
DED 316 L cylindrical tubes
In order to analyze the effect of heat treatment, cylinder height, batch of specimen and
day on the external roundness of DED 316 L cylindrical tubes, a Design of Analysis
experiment was conducted. The factors of interest were:
• Heat Treatment (0: before HT; 1: After HT )
• Circle height (1:close to substrate up to 15: top position of cylinder)
• Order in Batch (1,2,3,4) and Day (1,2,3).
The results obtained were:
Data Snooping
Main Effect Plot
From the main effect plot, it seems that circle height has significant impact on the
external roundness of DED 316 L stainless steel tubes.
Figure 5-1. Main Effect Plot for External Roundness
55
Box Plot
From the box plot it seems that the external roundness was decreasing along the
length of cylinder. It indicates that specimens produced are not perfect cylinders.
Moreover, Heat treatment seems to have positive impact on the external roundness
of specimens as both the mean value and variance of external roundness after heat
treatment reduced.
Figure 5-2. Box Plot of External Roundness before and after Heat treatment along the length of cylinder
Interaction Plot
From Figure 5.3, interaction seems to be present between order in batch-day and day-
circle height, since the lines of interaction plot are not parallel. But interaction cannot
be evaluated because order in batch and day are considered as blocking factor.
Figure 5-3. Interaction plot for External Roundness
Circle Height
Heat Treatment
151413121110987654321
101010101010101010101010101010
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
Exte
rnal
Ro
un
dn
ess
Boxplot of External Roundness
56
ANALYSIS
Analysis of Variance
Source DF Adj SS Adj MS F-Value P-Value
order in Batch 3 0.1395 0.04650 3.58 0.014
Day 2 0.3374 0.16870 12.97 0.000
Circle Height 14 1.9051 0.13608 10.47 0.000
Heat Treatment 1 0.1583 0.15831 12.17 0.001
Error 339 4.4080 0.01300
Total 359 6.9483
Model Summary
S R-sq R-sq(adj) R-sq(pred)
0.114030 36.56% 32.82% 28.46%
Table 5-1. ANOVA Table for External Roundness
From the ANOVA table, since the p value of factor order in Batch, Day, Circle height,
Heat Treatment are less than significance level (5 %) it seems that circle height, Heat
Treatment , and the blocking factor order in batch and day are significant factors.
Residual Analysis
Normality
The normality test for standardized residuals is not verified.
Figure 5-4. Normality plot of Standardized Residuals
57
Scatter Plot
The scatter plot of SRES vs fits shows particular pattern. Moreover, the standardized
residuals are not inside the interval (-3,3). The variance among levels does not appear
to be homogeneous.
Figure 5-5. Scatter Plot of SRES VS FITS
BOX COX Transformation
In order to improve the analysis, BOX COX transformation was applied.
Box Cox transformation
Rounded λ -2
Estimated λ -1.91169
95% CI for λ (-2.20319, -1.63319)
Table 5-2. Box Cox Transformation Analysis of Variance for Transformed Response
Source DF Adj SS Adj MS F-Value P-Value
order in Batch 3 6429 2143.1 6.56 0.000
Day 2 875 437.5 1.34 0.264
Circle Height 14 26683 1905.9 5.83 0.000
Heat Treatment 1 2094 2094.2 6.41 0.012
Error 339 110804 326.9
Total 359 146886
Model Summary for Transformed Response
S R-sq R-sq(adj) R-sq(pred)
18.0792 24.56% 20.11% 14.93%
Table 5-3. ANOVA TABLE for Transformed External Roundness
From the ANOVA table, it seems that the factor circle height, Heat Treatment and the
blocking factor order in Batch have p value less than the significance level (5 %) and
appears to be significant.
0.40.20.0 3.52.51.5 321
4
2
0
-2
15105
4
2
0
-2
1.00.50.0
FITS1
SR
ES1
order in Batch Day
Circle Height Heat Treatment
Scatterplot of SRES1 vs FITS1, order in Bat, Day, Circle Heigh, ...
58
Residual Analysis
Normality Plot
The p value for normality test is 0.107 which is higher than significance level (5 %).
Therefore, Normality assumption is satisfied
Figure 5-6. Normality Plot of Standardized Residuals
Scatter Plot
The scatter plot of standardized residuals vs fits indicates no particular pattern. The
standardized residuals are inside the interval (-3,3) and the homogeneity of variance
seems to be ok.
Figure 5-7. Scatter plot of SRES Vs FITS
Since the normality and homogeneous variance is satisfied, we conclude that external
roundness of DED 316 L stainless steel tubes depend on the circle height, order in
Batch and the Heat Treatment.
-20-40-60 3.52.51.5 321
2
0
-2
-4
15105
2
0
-2
-4
1.00.50.0
FITS2
SRES
2
order in Batch Day
Circle Height Heat Treatment
Scatterplot of SRES2 vs FITS2, order in Bat, Day, Circle Heigh, ...
59
Multiple Comparison
Tukey Pairwise Comparisons: Response = external roundness Term = Circle Height
Tukey pairwise comparison with confidence level of (97.5 %) was carried out on the
circle height and Heat Treatment.
Grouping Information Using the Tukey Method and 97.5% Confidence
Circle
Height N Mean Grouping
1 24 0.218033 A
2 24 0.174826 A B
3 24 0.167802 A B C
15 24 0.161602 A B C D
14 24 0.160471 A B C D
4 24 0.158118 B C D
12 24 0.151719 B C D
13 24 0.151017 B C D
11 24 0.147392 B C D
5 24 0.147090 B C D
10 24 0.143690 B C D
6 24 0.139871 B C D
8 24 0.139151 C D
7 24 0.138018 C D
9 24 0.135134 D
Means that do not share a letter are significantly different.
Table 5-4. Post ANOVA Analysis of External Roundness with circle height
From the Tukey comparison, it appears that circles 1, 2, 3 which were close to the
substrate were significantly different from the rest. Moreover, as we move along the
height of cylindrical tubes, the external roundness was decreasing.
Tukey Pairwise Comparisons: Response = external roundness Term = Heat Treatment
Grouping Information Using the Tukey Method and 97.5% Confidence
Heat
Treatment N Mean Grouping
0 180 0.157044 A
1 180 0.148461 B
Means that do not share a letter are significantly different.
Table 5-5. Post ANOVA Analysis of External Roundness with Heat Treatment
From the Tukey comparison, we can conclude that Heat Treatment had a positive
impact on the external roundness of DED 316 L cylindrical tubes since heat treatment
had significantly reduced the external roundness.
60
Conclusion
Since the factor order in Batch is significant, we found out that external roundness was
different for different specimens. Moreover, external roundness was changing along
the length of cylinder. Since the roundness was decreasing along the cylinder height,
it indicates that specimens produced were not perfect cylinders. This is because of the
uncontrolled growing of the layer at the beginning of the process which causes the
deposition layers close to the substrate to be different from the others. Afterwards, a
uniform layer thickness of 0.2 mm was maintained.
Moreover, since Heat Treatment is significant, it means that heat treatment had an
impact on the external roundness. After heat treatment, external roundness has
decreased, and the variance appears more homogeneous. This is attributed to the
stress relief effect that can cause detachment of the excess sinterized particles.
61
5.1.2 Effect of Cylinder Height and Heat Treatment on Internal Roundness of
DED 316 L cylindrical tubes
In order to analyze the effect of heat treatment, cylinder height, order in batch of
specimen and day on the internal roundness of DED 316 L stainless steel cylindrical
tubes, a Design of Analysis experiment was conducted. The factor of interest were
Heat Treatment (0: before HT; 1: After HT), circle height ( 1:close to substrate, up to
15: top position of cylinder) , order in Batch (1,2,3,4) and Day (1,2,3). The results
obtained were:
Box Plot
From the box plot it seems that the internal roundness was decreasing along the length
of cylinder. It indicates that specimens produced are not perfect cylinders. Moreover,
Heat treatment seems to have little impact on the internal roundness of specimens.
Figure 5-8. Box plot of Internal Roundness before and after Heat Treatment along the length of
cylinder
Circle Height
Heat Treatment
151413121110987654321
101010101010101010101010101010
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Inte
rnal
Ro
un
dn
ess
Boxplot of Internal Roundness
62
Main Effect plot
From the main effect plot, it seems that circle height has significant impact on the
internal roundness of DED 316 L stainless steel cylindrical tubes.
Figure 5-9. Main Effect plot of Internal Roundness
Interaction Plot
From the interaction plot, it seems that there is interaction between order in batch
batch-day, day and Heat Treatment. But since order in batch and day are blocking
factors, the interaction cannot be evaluated.
Figure 5-10. Interaction plot of Internal Roundness
ANALYSIS
63
Analysis of Variance
Source DF Adj SS Adj MS F-Value P-Value
order in Batch 3 0.2041 0.06803 3.29 0.021
Day 2 0.8912 0.44559 21.55 0.000
Circle Height 14 5.2391 0.37422 18.10 0.000
Heat Treatment 1 0.0788 0.07880 3.81 0.052
Error 339 7.0096 0.02068
Total 359 13.4228
Model Summary
S R-sq R-sq(adj) R-sq(pred)
0.143796 47.78% 44.70% 41.11%
Table 5-6. ANOVA Analysis of Internal Roundness
From the ANOVA Table, it seems that factor circle height, Heat Treatment and
blocking factor order in Batch and day are significant.
Residual Analysis
Normality
The normality assumption of standardized residuals is not satisfied.
Figure 5-11. Normality plot of Standardized Residuals
Scatter Plot
64
The scatter plot of SRES vs fits shows particular pattern. Moreover, the standardized
residuals are not inside the interval (-3,3). The variance among levels does not appear
to be homogeneous.
Figure 5-12. Scatter plot of Standardized Residuals VS Fits
Box COX Transformation
In order to improve the analysis, box cox transformation was applied
Box Cox transformation
Rounded λ -1.37191
Estimated λ -1.37191
95% CI for λ (-1.62341, -1.12941)
Table 5-7. Box Cox Transformation for Internal Roundness Analysis of Variance for Transformed Response
Source DF Adj SS Adj MS F-Value P-Value
order in Batch 3 237.90 79.300 5.96 0.001
Day 2 292.82 146.412 11.00 0.000
Circle Height 14 2116.52 151.180 11.36 0.000
Heat Treatment 1 0.00 0.000 0.00 0.996
Error 339 4512.51 13.311
Total 359 7159.75
Model Summary for Transformed Response
S R-sq R-sq(adj) R-sq(pred)
3.64846 36.97% 33.26% 28.92%
Table 5-8. ANOVA Table for Internal Roundness
From the ANOVA table, it seems that circle height, and blocking factor order in batch
and day appears to be significant. Since the p value of Heat Treatment is 0.996, it
seems that heat treatment had no impact on the internal roundness of DED 316 L SS
cylindrical tubes.
0.500.250.00 3.52.51.5 321
4
2
0
-2
15105
4
2
0
-2
1.00.50.0
FITS1
SRES
1
order in Batch Day
Circle Height Heat Treatment
Scatterplot of SRES1 vs FITS1, order in Bat, Day, Circle Heigh, ...
65
Residual Analysis
Normality plot
Even after box cox transformation, the assumption for normality of standardized
residuals is not satisfied.
Figure 5. 13: Normality plot of Standardized Residuals
Scatter plot
The scatter plot of standardized residuals vs fits indicates no particular pattern. The
standardized residuals are inside the interval (-3,3) and the homogeneity of variance
seems to be ok.
Figure 5. 14: Scatter plot of Standardized Residuals Vs Fits
Since the assumption of homogenous variance is satisfied. The assumption of
normality can be improved if we consider the interaction factor. Because of blocking
factor, interaction cannot be evaluated. We know that, Minitab analysis is quite robust
towards normality assumption, hence we can conclude that circle height, order in
batch and day are significant factors while Heat Treatment has no impact.
-5-10-15 3.52.51.5 321
2
0
-2
15105
2
0
-2
1.00.50.0
FITS2
SRES
2
order in Batch Day
Circle Height Heat Treatment
Scatterplot of SRES2 vs FITS2, order in Bat, Day, Circle Heigh, ...
66
Multiple Comparison
Tukey Pairwise Comparisons: Response = Internal Roundness, Term = Circle Height Tukey pair wise comparison with confidence level of (95 %) was carried out on the
circle height.
Grouping Information Using the Tukey Method and 95% Confidence
Circle
Height N Mean Grouping
1 24 0.291869 A
2 24 0.287341 A
3 24 0.254795 A B
4 24 0.228417 A B C
5 24 0.211636 A B C D
6 24 0.205530 A B C D E
7 24 0.189077 B C D E F
14 24 0.176407 C D E F
8 24 0.173959 C D E F
15 24 0.170500 D E F
13 24 0.165605 D E F
12 24 0.164603 D E F
11 24 0.161192 E F
10 24 0.160139 F
9 24 0.159575 F
Means that do not share a letter are significantly different.
Table 5-9. Post ANOVA Analysis of Internal Roundness with circle height
CONCLUSION
Since we have circle height significant, we can conclude that internal roundness is
changing along the length of cylinder. In particular from the results of Multiple
comparison, we come to know that internal roundness was decreasing along the
length of cylinder. Therefore, the 316 L tubes produced by Direct Energy Deposition
are not perfect cylinders. The internal roundness was higher for the layers close to the
substrate due to uncontrolled deposition of the layer at the beginning of the process.
Moreover, the blocking factor order in batch and day are significant. We can conclude
that internal roundness was different for different specimens. Even the fact that
specimens produced in different days had an impact on the internal roundness of the
DED 316 L stainless steel cylindrical tubes.
67
5.1.3 Effect of cylinder height and heat treatment on the internal diameter of
DED 316 L stainless steel cylindrical tubes
In order to analyze the effect of heat treatment, cylinder height, order in batch of
specimen and day on the internal diameter of DED 316 L stainless steel cylindrical
tubes, a Design of Analysis Experiment was conducted. The factors of interest were
Heat Treatment (0: before HT; 1: After HT), circle height (1: close to substrate up to
15: top position of cylinder), order in Batch (1, 2, 3, 4) and Day (1, 2, 3). The results
obtained were:
Data Snooping
Box Plot
From the box plot it seems that the internal diameter was decreasing along the length
of cylinder. It indicates that specimens produced are not perfect cylinders. Moreover,
Heat treatment seems to have an impact on the internal diameter of specimens as the
mean value seems to increase and the variance appears more uniform.
Figure 5. 15: Box Cox Plot of Internal Diameter of DED 316 L cylindrical tubes along the length of cylinder
Main Effect Plot
From the main effect plot, it seems that circle height has major impact on the internal
diameter of DED 316 L stainless steel cylindrical tubes.
Circle Height
Categorical Var
151413121110987654321
101010101010101010101010101010
32.50
32.25
32.00
31.75
31.50
inte
rnal
dia
mete
r (m
m)
Boxplot of internal diameter
68
Figure 5. 16: Main Effect plot of internal diameter
Interaction Plot
Interaction seems to be present between order in Batch-Day and Day-Heat Treatment
as the lines are not parallel. But interaction cannot be evaluated because order in
Batch and Day are considered as blocking factor.
Figure 5. 17: Interaction plot of Internal Diameter
ANALYSIS
Analysis of Variance
Source DF Adj SS Adj MS F-Value P-Value
order in Batch 3 0.0716 0.02386 1.32 0.268
Day 2 0.1526 0.07632 4.21 0.016
Circle Height 14 5.2264 0.37331 20.62 0.000
Heat Treatment 1 0.1211 0.12110 6.69 0.010
Error 339 6.1388 0.01811
Total 359 11.7106
Model Summary
69
S R-sq R-sq(adj) R-sq(pred)
0.134569 47.58% 44.49% 40.88%
Table 5-10. ANOVA Analysis of Internal Diameter From the ANOVA table, it seems that circle height, Heat Treatment and blocking factor
day are significant. Since the circle height is significant, it indicates that the internal
diameter of the tube is varying along the length of the tube. Moreover since the
blocking factor DAY is significant, therefore, batch of tubes produced under similar
condition, but on different days were not perfectly identical. Heat treatment had an
impact on the internal diameter of the tubes
Residual Analysis
Normality
From the graph, we see that the normality assumption of standardized residuals is not
satisfied. Since the residual assumptions are not satisfied, we have to make a data
transformation so that the residual assumptions are satisfied before concluding from
the ANOVA results
Figure 5. 18: Normality plot of Standardized Residuals
Scatter Plot
The scatter plot of SRES vs fits shows particular pattern. Moreover, the standardized
residuals are not inside the interval (-3,3). The variance among levels does not appear
to be homogeneous.
70
Figure 5. 19: Scatter Plot of SRES vs FITS
Box Cox Transformation
In order to improve the analysis, Box cox transformation was applied.
Box Cox transformation
Rounded λ -2.88137
Estimated λ -2.88137
95% CI for λ (-2.88387, -2.87787)
Table 5-11. Box Cox transformation of Internal diameter Analysis of Variance for Transformed Response
Source DF Adj SS Adj MS F-Value P-Value
order in Batch 3 0.0702 0.02339 1.31 0.271
Day 2 0.1488 0.07440 4.17 0.016
Circle Height 14 5.2181 0.37272 20.87 0.000
Heat Treatment 1 0.1241 0.12415 6.95 0.009
Error 339 6.0536 0.01786
Total 359 11.6148
Model Summary for Transformed Response
S R-sq R-sq(adj) R-sq(pred)
0.133631 47.88% 44.81% 41.22%
Table 5-12. ANOVA Table for Internal Diameter (Transformed Response)
From the ANOVA table, it seems that circle height, Heat Treatment and blocking factor
day are significant factors.
Residual Analysis
Normality
32.031.831.6 3.52.51.5 321
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2
0
-2
-4
15105
4
2
0
-2
-4
1.00.50.0
FITS1
SRES
1
order in Batch Day
Circle Height Heat Treatment
Scatterplot of SRES1 vs FITS1, order in Bat, Day, Circle Heigh, ...
71
From the graph, we see that even after applying box cox transformation, the normality
assumption is not satisfied.
Figure 5. 20: Normality plot of Standardized Residuals
Scatter Plot
Even after box cox transformation, the scatter plot indicates no improvement. There
seems to be pattern among SRES and fits. Moreover, the variance among levels does
not appears homogeneous.
Figure 5. 21: Scatter plot of Standardized residuals Vs fits
Removing outliers
In order to improve the analysis, some outliers were removed, and the analysis was
reperformed by applying box cox transformation.
Box-Cox transformation
Rounded λ -3
Estimated λ -2.6352
95% CI for λ (*, *)
Table 5-13. Box Cox Transformation for Internal diameter (removing outliers)
240092.2240092.0240091.8 3.52.51.5 321
4
2
0
-2
-4
15105
4
2
0
-2
-4
1.00.50.0
FITS2
SR
ES2
order in Batch Day
Circle Height Heat Treatment
Scatterplot of SRES2 vs FITS2, order in Bat, Day, Circle Heigh, ...
72
Analysis of Variance for Transformed Response
Source DF Adj SS Adj MS F-Value P-Value
order in Batch 3 0.0839 0.02796 1.70 0.167
Day 2 0.1930 0.09649 5.86 0.003
Circle Height 14 4.9741 0.35529 21.58 0.000
Heat Treatment 1 0.1047 0.10474 6.36 0.012
Error 336 5.5308 0.01646
Total 356 10.8921
Model Summary for Transformed Response
S R-sq R-sq(adj) R-sq(pred)
0.128300 49.22% 46.20% 42.55%
Table 5-14. ANOVA Table for internal diameter (Removing outliers)
From ANOVA Table, it seems that circle height, Heat Treatment and blocking factor
Day are significant factors.
Residual Analysis
Normality Normality assumption was not satisfied.
Figure 5. 22: Normality plot of Standardized Residuals
Scatter Plot
By removing outliers and applying box cox transformation, the scatter plot of
standardized residuals vs fits indicates no trend. The standardized residuals are inside
the interval (-3,3) and the homogeneity of variance seems to be ok.
73
Figure 5. 23: Scatter Plot of Standardized Residuals Vs Fits
Multiple Comparison
Tukey Pairwise Comparisons: Response = internal diameter_1, Term = Circle Height Tukey pairwise comparison with confidence level of (97.5 %) was carried out on circle
height and Heat Treatment. From the post ANOVA analysis, we can conclude that
internal diameter was decreasing along the length of DED 316 L stainless steel
cylindrical tubes. The tubes produced were not perfect cylinders.
Grouping Information Using the Tukey Method and 97.5% Confidence
Circle
Height N Mean Grouping
5 24 32.0665 A
6 24 32.0651 A
4 24 32.0602 A
2 24 32.0554 A
3 24 32.0486 A
7 24 32.0480 A
8 24 32.0209 A B
1 21 32.0156 A B
9 24 31.9864 A B C
10 24 31.9462 A B C D
11 24 31.9009 B C D
12 24 31.8590 C D E
13 24 31.8156 D E F
14 24 31.7555 E F
15 24 31.7071 F
Means that do not share a letter are significantly different
Table 5-15. Post ANOVA Analysis of Internal Diameter vs circle height Tukey Pairwise Comparisons: Response = internal diameter_1Term = Categorical Var
347638.4347638.2347638.0 3.52.51.5 321
2
0
-2
-4
15105
2
0
-2
-4
1.00.50.0
FITS3
SRES
3
order in Batch Day
Circle Height Heat Treatment
Scatterplot of SRES3 vs FITS3, order in Bat, Day, Circle Heigh, ...
74
From the Post ANOVA Analysis, we conclude that heat treatment had an impact on
the internal diameter of the DED 316 L cylindrical tubes. And that internal diameter of
additive tubes is increased by heat treatment.
Grouping Information Using the Tukey Method and 97.5% Confidence
Heat
Treatment N Mean Grouping
1 178 31.9730 A
0 179 31.9388 B
Means that do not share a letter are significantly different.
Table 5-16. Post ANOVA Analysis of Internal Diameter vs Categorical variable
Conclusion
Since circle height is significant, and from the Analysis, we can conclude that internal
diameter was decreasing along the height of DED 316 L stainless steel cylindrical
tubes. As a result, we conclude that DED 316 L specimens were not perfect cylinders
and there was conicity in the tubes. Moreover, the blocking factor DAY is significant,
therefore, batch of tubes produced under similar condition, but on different days were
not perfectly identical.
75
5.1.4 Effect of cylinder height and heat treatment on the external diameter of
DED 316 L Cylindrical tubes
In order to analyze the effect of heat treatment, cylinder height, order in batch of
specimen and day on the external diameter of DED 316 L stainless steel cylindrical
tubes, a Design of Analysis experiment was conducted. The factors of interest were
Heat Treatment (0: before HT; 1: After HT), circle height (1: close to substrate; up to
15: top position of cylinder), order in Batch (1, 2, 3, 4) and Day (1, 2, 3). The results
obtained were:
Data Snooping
Box Plot
From the box plot it seems that the external diameter was decreasing along the length
of cylinder. It indicates that specimens produced are not perfect cylinders. Moreover,
Heat treatment seems to have an impact on the external diameter of specimens as
mean value of external diameter seems to have decreased and the variance appears
to be more homogeneous.
Figure 5. 24: Box plot of external diameter with circle height
Circle Height
Categorical Var
151413121110987654321
101010101010101010101010101010
35.4
35.2
35.0
34.8
34.6
34.4
34.2
exte
rnal
dia
mete
r (m
m)
Boxplot of external diameter
76
Main Effect plot
From the main effect plot, it seems that circle height has major impact on the external
diameter of DED 316 L stainless steel cylindrical tubes.
Figure 5. 25: Main Effect Plot of External Diameter Interaction Plot
From the interaction plot, there seems to be an interaction present between order in
Batch-day, but it cannot be evaluated since they are blocking factors
Figure 5. 26: Interaction Plot of external diameter
77
ANALYSIS
Analysis of Variance
Source DF Adj SS Adj MS F-Value P-Value
order in Batch 3 0.0858 0.02860 8.71 0.000
Day 2 1.1570 0.57852 176.11 0.000
Circle Height 14 16.6772 1.19123 362.63 0.000
Heat Treatment 1 0.0948 0.09484 28.87 0.000
Error 339 1.1136 0.00328
Total 359 19.1285
Model Summary
S R-sq R-sq(adj) R-sq(pred)
0.0573145 94.18% 93.83% 93.43%
Table 5-17. ANOVA Table for external diameter
From the ANOVA table, we could say that the factors, Circle height, Heat Treatment,
blocking factors order in Batch and Day seems to be significant since their p values
are less than the significance level (5 %).
Residual Analysis
Normality Plot
The p value for normality test is < 0.005. Hence, the normality test for standardized
residuals is not verified.
Figure 5. 27: Normality plot for Standardized Residuals
78
Scatter Plot
The scatter plot of SRES vs fits shows particular pattern. Moreover, the standardized
residuals are not inside the interval (-3,3). The variance among levels does not appear
to be homogeneous.
Figure 5. 28: Scatter plot of Standardized residuals
Box Cox Transformation
Since the assumptions of normality and homogenous variance for standardized
residuals is not satisfied, we tried to improve the analysis by Box Cox Transformation.
Box Cox transformation
Rounded λ -2.86788
Estimated λ -2.86788
95% CI for λ (-2.86838, -2.86738)
Table 5-18. BOX Cox Transformation
Analysis:
Analysis of Variance for Transformed Response
Source DF Adj SS Adj MS F-Value P-Value
order in Batch 3 0.0831 0.02770 9.28 0.000
Day 2 1.1310 0.56548 189.35 0.000
Circle Height 14 16.5996 1.18568 397.02 0.000
Heat Treatment 1 0.0902 0.09015 30.19 0.000
Error 339 1.0124 0.00299
Total 359 18.9162
Model Summary for Transformed Response
S R-sq R-sq(adj) R-sq(pred)
0.0546485 94.65% 94.33% 93.96%
Table 5-19. ANOVA Table after Box Cox Transformation
35.234.834.4 3.52.51.5 321
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4
2
0
-2
15105
6
4
2
0
-2
1.00.50.0
FITS1
SR
ES1
order in Batch Day
Circle Height Heat Treatment
Scatterplot of SRES1 vs FITS1, order in Bat, Day, Circle Heigh, ...
79
From the transformed ANOVA Table, we could say that the factors Circle Height, Heat
Treatment, and blocking factor order in Batch and Day appears to be significant since
their p value is less than the significance level (5 %)
Residual Analysis
Normality Plot From the normality plot, we see that box cox transformation has no impact on the normality of standardized residuals.
Figure 5. 29: Normality plot of Standardized Residuals
Scatter Plot
Even after applying box cox transformation, the scatter plot of SRES vs fits indicates
the presence of trend. Moreover, the standardized residuals are not inside the interval
(-3,3). The variance among levels does not appear to be homogeneous.
Figure 5. 30 : Scatter plot of Standardized Residuals vs Fits
313684.5313684.0313683.5 3.52.51.5 321
6
4
2
0
-2
15105
6
4
2
0
-2
1.00.50.0
FITS2
SR
ES2
order in Batch Day
Circle Height Heat Treatment
Scatterplot of SRES2 vs FITS2, order in Bat, Day, Circle Heigh, ...
80
Removing outliers
In order to further improve analysis, I removed outliers and applied box cox
transformation. The results were:
Box Cox transformation
Rounded λ -2
Estimated λ -2.10969
95% CI for λ (*, *)
Table 5-20. Box Cox Transformation
Analysis of Variance for Transformed Response
Source DF Adj SS Adj MS F-Value P-Value
order in Batch 3 0.000000 0.000000 33.10 0.000
Day 2 0.000000 0.000000 530.26 0.000
Circle Height 14 0.000000 0.000000 1460.90 0.000
Heat Treatment 1 0.000000 0.000000 24.33 0.000
Error 310 0.000000 0.000000
Total 330 0.000000
Model Summary for Transformed Response
S R-sq R-sq(adj) R-sq(pred)
0.0000011 98.55% 98.46% 98.33%
Table 5-21. ANOVA Table for External Diameter
From ANOVA table, we see that after removing outliers and applying box cox
transformation, the results of ANOVA table showed no difference. It seems that
factors, Circle Height, Heat Treatment, and blocking factors order in Batch and Day
are significant.
Residual Analysis Normality Plot The normality plot of standardized residuals seems to have improved. But still the
assumption for normality of standardized residuals is not verified.
Figure 5. 31: Normality Plot of Standardized Residuals
81
Scatter Plot
By removal of outliers and applying box cox transformation, the scatter plot of SRES
vs fits shows pattern. Moreover, the standardized residuals are not inside the interval
(-3,3). The variance among levels does not appear to be homogeneous.
Figure 5. 32: Scatter Plot of Standardized Residuals vs FITS
From our analysis, we could conclude that the assumption of normality and
homogenous variance for standardized residuals is not satisfied. But we know that,
Minitab analysis is quite robust towards assumptions for standardized residuals, hence
we can conclude that the factors Circle height, Heat Treatment and the blocking
factors order in Batch and day are significant factors.
Multiple Comparison
Tukey pairwise comparison with confidence level of (97.5%) was performed on circle
height and Heat Treatment.
Tukey Pairwise Comparisons: Response = external diameter_1_1, Term = Circle Height
From the Post ANOVA analysis, we can conclude that external diameter was
increasing along the length of DED 316 L stainless steel cylindrical tubes.
-0.000825-0.000840-0.000855 3.52.51.5 321
4
2
0
-2
-4
15105
4
2
0
-2
-4
1.00.50.0
FITS3
SR
ES
3
order in Batch Day
Circle Height Heat Treatment
Scatterplot of SRES3 vs FITS3, order in Bat, Day, Circle Heigh, ...
82
Grouping Information Using the Tukey Method and 97.5% Confidence
Circle
Height N Mean Grouping
1 15 34.8931 A
2 16 34.8632 A
3 19 34.8317 B
4 21 34.7973 C
5 22 34.7574 D
6 23 34.7138 E
7 23 34.6609 F
8 24 34.6129 G
9 24 34.5591 H
10 24 34.5152 I
11 24 34.4740 J
12 24 34.4337 K
13 24 34.3874 L
14 24 34.3308 M
15 24 34.2768 N
Means that do not share a letter are significantly different.
Table 5-22. Post ANOVA Analysis of External Diameter vs circle height
Tukey Pairwise Comparisons: Response = external diameter_1_1, Term = Heat Treatment From the Post ANOVA analysis, we can conclude that Heat Treatment had an impact
on the external diameter. In particular, the external diameter of DED 316 L stainless
steel cylindrical tubes has reduced after Heat treatment.
Grouping Information Using the Tukey Method and 97.5% Confidence
Heat
Treatment N Mean Grouping
0 158 34.6120 A
1 173 34.5990 B
Means that do not share a letter are significantly different.
Table 5-23. Post ANOVA Analysis of External Diameter vs Heat Treatment
CONCLUSION
Since the factor order in Batch is significant, we conclude that the external diameter
was different for different specimens of DED 316 L stainless steel. Moreover, the
external diameter was changing along the length of cylindrical tubes. Since the
external diameter is not homogenous along the length of DED 316 L cylindrical tubes,
we can conclude that the cylindrical tubes produced using Direct Energy Deposition
method were not perfect cylinders and there is some conicity in the tubes. The layers
close to the substrate are different from the others because of uncontrolled growing of
the layers at the beginning of the process. Moreover, since Heat Treatment is
significant, it means that heat treatment had an impact on the external diameter of
DED 316 L stainless steel cylindrical tubes. After heat treatment, external diameter
has decreased, and the variance appears more homogeneous.
83
5.1.5 Effect of cylinder height and heat treatment on the internal cylindricity of
DED 316 L Cylindrical tubes
In order to analyze the effect of heat treatment, batch of specimen and day on the
internal cylindricity of DED 316 L stainless steel cylindrical tubes, a Design of Analysis
experiment was conducted. The factors of interest were Heat Treatment (0: before HT;
1: After HT), Batch (1,2,3,4) and Day (1,2,3). The results obtained were:
Data Snooping
Box Plot
From the box plot, the mean value of internal cylindricity before and after heat
treatment appears to be same, but the variance appears to be more homogeneous.
Figure 5. 33: Box Plot of internal cylindricity before and after heat treatment
internal cylindricity after HTinternal cylindricty before HT
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
Data
Boxplot of internal cylindricty bef, internal cylindricity af
84
Main Effect Plot
From the main effect plot, the blocking factor day seems to be the most significant
factor.
Figure 5. 34: Main Effect plot for internal cylindricity
Interaction Plot
From the interaction plot, an interaction between Batch- Day, Day-Heat Treatment
seems to be present.
Figure 5. 35: Interaction plot for internal cylindricity
85
Analysis
Analysis of Variance
Source DF Adj SS Adj MS F-Value P-Value
Batch 3 0.05764 0.01921 0.58 0.639
Day 2 0.30581 0.15291 4.58 0.026
Heat Treatment 1 0.07149 0.07149 2.14 0.162
Error 17 0.56772 0.03340
Total 23 1.00266
Model Summary
S R-sq R-sq(adj) R-sq(pred)
0.182744 43.38% 23.39% 0.00%
Table 5-24. ANOVA Table for Internal Cylindricity
From the ANOVA table, it seems that only blocking factor day is significant. An
improvement in the model seems to be required by considering the interaction but
interaction cannot be evaluated because of the presence of blocking factor.
Residual Analysis
Normality Plot
The p value for normality test is 0.701 which is much higher than the significance level
(5 %). Therefore, the assumption for normality of standardized residuals is verified.
Figure 5. 36: Normality plot of Standardized Residuals
86
Scatter Plot
The scatter plot of standardized residuals vs fits indicates no particular pattern. The
standardized residuals are inside the interval (-3,3) and the homogeneity of variance
seems to be ok.
Figure 5. 37: Scatter Plot of Standardized Residuals Vs Fits
CONCLUSION
Since, the assumptions of normality and homogenous variance for standardized
residuals is satisfied, we concluded that Heat Treatment had no impact on the internal
cylindricity of DED 316 L stainless steel cylindrical tubes. Only the blocking factor Day
was significant, hence we can conclude that internal cylindricity was different for
batches of tubes produced in different days.
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1
0
-1
-2
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1
0
-1
-2
1.000.750.500.250.00
FITS1
SR
ES
1
Batch
Day Heat Treatment
Scatterplot of SRES1 vs FITS1, Batch, Day, Heat Treatment
87
5.1.6 Effect of cylinder height and heat treatment on the external cylindricity of
DED 316 L Cylindrical tubes
In order to analyze the effect of heat treatment, batch of specimen and day on the
external cylindricity of DED 316 L stainless steel cylindrical tubes, a Design of Analysis
experiment was conducted. The factors of interest were Heat Treatment (0: before HT;
1: After HT, Batch (1, 2, 3, 4) and Day (1, 2, 3). The results obtained were:
Data Snooping
Box Plot From the box plot, the mean value of external cylindricity before and after heat
treatment appears to be same, but the variance appears to be more homogeneous.
Figure 5. 38: Box Plot of External Cylindricity
Main Effect Plot
From the main effect plot, the blocking factor day seems to be the most significant
factor.
Figure 5. 39: Main effect plot for External Cylindricity
External Cylind after HTexternal cylind before HT
1.0
0.9
0.8
0.7
0.6
0.5
0.4
Dat
a
Boxplot of external cylind before HT, External Cylind after HT
88
Interaction Plot
From the interaction plot, an interaction between Batch-Day, Day-Heat Treatment
seems to be present.
Figure 5. 40: Interaction plot for External Cylindricity
Analysis
Analysis of Variance
Source DF Adj SS Adj MS F-Value P-Value
Batch 3 0.04704 0.01568 0.76 0.533
Day 2 0.20163 0.10082 4.87 0.021
Heat Treatment 1 0.04546 0.04546 2.20 0.157
Error 17 0.35164 0.02068
Total 23 0.64578
Model Summary
S R-sq R-sq(adj) R-sq(pred)
0.143822 45.55% 26.33% 0.00%
Table 5-25. ANOVA Table for External Cylindricity
From the ANOVA table, it seems that only blocking factor day is significant since its p
value is less than the significance level of (5%). An improvement in the model seems
to be required by considering the interaction but interaction cannot be evaluated
because of the presence of blocking factor.
Residual Analysis
Normality Plot
The p value for normality test is 0.888 which is much higher than the significance level
(5 %). Therefore, the assumption for normality of standardized residuals is verified.
89
Figure 5. 41: Normality Plot for Standardized Residuals
Scatter Plot
The scatter plot of standardized residuals vs fits indicates no pattern. The standardized
residuals are inside the interval (-3,3) and the homogeneity of variance seems to be
ok.
Figure 5. 42: Scatter Plot of Standardized Residuals Vs Fits
CONCLUSION
Since, the assumptions of normality and homogenous variance for standardized
residuals is satisfied, we concluded that Heat Treatment had no impact on the external
cylindricity of DED 316 L tubes. Only the blocking factor Day was significant, hence
we can conclude that external cylindricity was different for tubes produced in different
days.
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1
0
-1
-2
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SRES
1
Batch
Day Heat Treatment
Scatterplot of SRES1 vs FITS1, Batch, Day, Heat Treatment
90
Reduced Model
5.1.7 Effect of Cylinder height, Heat Treatment, substrate removal, turning on
the external roundness of DED 316 L cylindrical tubes
Roundness is a measure of how closely the shape of an object approaches to that of
a perfect circle.
In order to analyze the effect of heat treatment, substrate removal by wire EDM and
turning, a Design of Analysis Experiments was performed on the cylinder. Since, a
part of the cylinder is machined, so in the combined analysis, I considered only the
portion that has been turned. The factors of interest were batch (1, 2, 3, 4), Day (1, 2,
3), Cate (0: As built, 1: After Heat Treatment, 2: After substrate removal, 3: After
turning), height (10, 11, 12, 13, 14, 15).
The results obtained were:
Box Plot
From the box plot, it seems that external roundness after substrate removal and
turning is significantly different from the as built and after heat treatment. After
machining, the absolute value of external roundness seems to have improved.
Figure 5. 43: External Roundness of DED 316 L after complete process chain
Exte
rnal R
oundne
ss a
fter t
urnin
Exte
rnal R
oudne
ss after
sub R
em
Exte
rnal ro
undnes
s af
ter H
T
Exte
rnal R
oundnes
s bef
ore H
T
0.20
0.15
0.10
0.05
0.00
Data
Boxplot of External Rou, External rou, External Rou, External Rou
91
Main Effect Plot
From the main effect plot, it seems that the variable cate appears to be significant.
Figure 5. 44: Main Effect plot of external roundness of DED 316 L after complete process chain
Interaction Plot
From figure 5.45, interaction between batch-day seems to be present. Since they are
blocking factors, so interaction cannot be evaluated.
Figure 5. 45: Interaction Plot for External Roundness of DED 316 L after complete process chain
92
ANALYSIS
Analysis of Variance
Source DF Adj SS Adj MS F-Value P-Value
batch 3 0.003578 0.001193 4.69 0.003
Day 2 0.015108 0.007554 29.71 0.000
Height 5 0.003111 0.000622 2.45 0.034
Cate 3 0.737260 0.245753 966.55 0.000
Error 274 0.069667 0.000254
Total 287 0.828724
Model Summary
S R-sq R-sq(adj) R-sq(pred)
0.0159455 91.59% 91.19% 90.71%
Table 5-26. ANOVA Table for External Roundness after complete process chain
From the ANOVA table, it seems that the factors Height, Cate and the blocking factors
batch and Day appears to be significant.
Residual Analysis
Normality Plot
The normality assumption of standardized residuals is not satisfied.
Figure 5. 46: Normality plot for Standardized Residuals
93
Scatter Plot
The scatter plot of standardized against fits shows a particular patter. The
standardized residuals are not inside the interval (-3,3). Moreover, the variance among
the levels do not appear to be homogenous.
Figure 5. 47: Scatter Plot of Standardized Residuals vs fits, batch, Day, Cate, Height
Box Cox Transformation
Box-Cox transformation
Rounded λ 1
Estimated λ 0.960853
95% CI for λ (0.853353, 1.07235)
Table 5-27. Box Cox Transformation of standardized residuals
ANALYSIS
Analysis of Variance
Source DF Adj SS Adj MS F-Value P-Value
batch 3 0.003578 0.001193 4.69 0.003
Day 2 0.015108 0.007554 29.71 0.000
Height 5 0.003111 0.000622 2.45 0.034
Cate 3 0.737260 0.245753 966.55 0.000
Error 274 0.069667 0.000254
Total 287 0.828724
Model Summary
S R-sq R-sq(adj) R-sq(pred)
0.0159455 91.59% 91.19% 90.71%
Table 5-28. ANOVA Table for External Roundness after Transformation
From the ANOVA Table, it seems that the factor height, cate and the blocking factor
batch and day appears to be significant.
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FITS1
SR
ES1
batch Day
Cate Height
Scatterplot of SRES1 vs FITS1, batch, Day, Cate, Height
94
Normality Plot
The normality assumption is still not satisfied.
Figure 5. 48: Normality Plot of Standardized Residuals
Scatter Plot
Even after applying box cox transformation, the homogeneity of variance assumption
does not appear to be satisfied. We try to remove outliers so that the homogeneity of
variance assumption for standardized residuals is satisfied.
Figure 5. 49: Scatter Plot of standardized residuals after box cox transformation
Removing Outliers
In order to improve the analysis, some outliers were removed, and the analysis was
reperformed after applying box cox transformation.
Box-Cox transformation
Rounded λ 1
Estimated λ 0.946481
95% CI for λ (0.841981, 1.05498)
Table 5-29. Box Cox Transformation after Removal of outliers
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FITS2
SRES
2
batch Day
Cate Height
Scatterplot of SRES2 vs FITS2, batch, Day, Cate, Height
95
ANOVA Table
From the ANOVA table, it seems that the factor height, cate and the blocking factor
batch and day appears to be significant.
Analysis of Variance
Source DF Adj SS Adj MS F-Value P-Value
batch 3 0.004076 0.001359 5.71 0.001
Day 2 0.015924 0.007962 33.46 0.000
Height 5 0.002901 0.000580 2.44 0.035
Cate 3 0.741859 0.247286 1039.12 0.000
Error 273 0.064967 0.000238
Total 286 0.828439
Model Summary
S R-sq R-sq(adj) R-sq(pred)
0.0154265 92.16% 91.78% 91.33%
Table 5-30. ANOVA Table for External Roundness after Removal of Outliers
Normality Plot
The normality assumption for standardized residuals is still not satisfied.
Figure 5. 50: Normality plot for Standardized Residuals
96
Scatter Plot
By removing outliers and after applying box cox transformation, the scatter plot of
standardized residuals vs fits indicates no trend. The standardized residuals are inside
the interval (-3,3) and the homogeneity of variance seems to be ok.
Figure 5. 51: Scatter Plot of standardized Residuals vs fits
Multiple Comparison
Tukey pairwise comparison with a confidence level of (97.5%) was carried out on
height and cate.
The Post ANOVA table reveals that the cylinder height from circle 10 to 15 are
identical.
Grouping Information Using the Tukey Method and 97.5% Confidence
Height N Mean Grouping
15 48 0.115372 A
14 48 0.111834 A
10 47 0.110755 A
12 48 0.108124 A
11 48 0.107235 A
13 48 0.105927 A
Means that do not share a letter are significantly different.
Table 5-31. POST ANOVA for External Roundness vs Height
From the multiple comparison table, it appears that external roundness has been
significantly improved after turning. While for the built and Heat treatment, the external
roundness appears to be same.
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FITS3
SRES
3
batch Day
Cate Height
Scatterplot of SRES3 vs FITS3, batch, Day, Cate, Height
97
Grouping Information Using the Tukey Method and 97.5% Confidence
Cate N Mean Grouping
1 72 0.157460 A
0 72 0.153852 A
2 72 0.095714 B
3 71 0.032472 C
Means that do not share a letter are significantly different.
Table 5-32. POST ANOVA for External Roundness Vs Cate
CONCLUSION
From Post ANOVA analysis of external roundness vs circle height, we see that the
external roundness was same along the length of the tube away from the substrate.
This validates the hypothesis that during the printing of the DED 316 L stainless steel
tubes, the process was unstable close to the substrate and there was uncontrolled
growing of the layers close to the substrate which then stabilizes and the cylinders
cylinders were deposited with a uniform layer thickness of 0.2 mm.
Heat Treatment had improved the dimensional quality of the tubs. This is associated
to the stress releasing effect due to heat treatment and the removal of excessive
powder materials attached to the DED 316 L stainless steel cylindrical tubes.
From our results, we can conclude that turning process has significantly improved the
external roundness of additive manufactured DED 316 L stainless steel cylindrical
tubes. Moreover, the blocking factor batch and day appears to be significant.
98
5.1.8 Effect of Cylinder height, Heat Treatment, substrate removal, turning on
the internal roundness of DED 316 L cylindrical tubes
In order to analyze the effect of heat treatment, substrate removal by wire EDM and
turning, a Design of Analysis Experiments was performed on the DED 316 L stainless
steel cylinder. Since, a part of the cylinder is machined, so in the combined analysis I
considered only the portion that has been turned. The factors of interest were batch
(1, 2, 3, 4), Day (1, 2, 3), Categorical (0: As built, 1: After Heat Treatment, 2: After
substrate removal, 3: After turning), height (13, 14, 15). The results obtained were:
Box Plot
From the box plot, it seems that internal roundness after substrate removal and turning
is significantly different from the as built and after heat treatment. After machining, the
absolute value of internal roundness seems to have improved.
Figure 5. 52: Internal Roundness of DED 316 L after complete process chain
Main Effect Plot
From the main effect plot, it seems that the variable cate appears to be significant.
Figure 5. 53: Main Effect Plot of Internal Roundness of DED 316 L after Complete Process chain
Inte
rnal
round
ness
after T
urni
n
Inte
rnal
Roun
dness
af s
ub rem
Inte
rnal
Roun
dness
afte
r HT
Inte
rnal
roun
dness b
f Ht
0.25
0.20
0.15
0.10
0.05
0.00
Dat
a
Boxplot of Internal rou, Internal Rou, Internal Rou, Internal rou
99
Interaction Plot
From figure 5.54, interaction between batch-day seems to be present. Since they are
blocking factors, so interaction cannot be evaluated.
Figure 5-54. Interaction Plot of Internal Roundness of DED 316 L after complete process chain
ANALYSIS
Analysis of Variance
Source DF Adj SS Adj MS F-Value P-Value
Batch 3 0.001831 0.000610 1.59 0.194
Day 2 0.001126 0.000563 1.47 0.234
Height 2 0.000672 0.000336 0.88 0.418
Categorical 3 0.405660 0.135220 353.09 0.000
Error 133 0.050933 0.000383
Total 143 0.460222
Model Summary
S R-sq R-sq(adj) R-sq(pred)
0.0195693 88.93% 88.10% 87.03%
Table 5-33. ANOVA Table for Internal Roundness
From the ANOVA Table, it seems that the factor categorical appears to be significant. Residual Analysis Normality Plot The normality assumption for standardized residuals is not satisfied.
Figure 5. 55: Normality Plot of Standardized Residuals
100
Scatter Plot:
The scatter plot of standardized residuals against fits shows a particular patter. The
standardized residuals are not inside the interval (-3,3). Moreover, the variance among
the levels do not appear to be homogenous.
Figure 5. 56: Scatter Plot of Standardized Residuals vs Fits
Box Cox Transformation
Box-Cox transformation
Rounded λ 1
Estimated λ 0.963913
95% CI for λ (0.762413, 1.17441)
Table 5-34. Box Cox Transformation for Standardized Residuals
ANALYSIS
Analysis of Variance
Source DF Adj SS Adj MS F-Value P-Value
Batch 3 0.001831 0.000610 1.59 0.194
Day 2 0.001126 0.000563 1.47 0.234
Height 2 0.000672 0.000336 0.88 0.418
Categorical 3 0.405660 0.135220 353.09 0.000
Error 133 0.050933 0.000383
Total 143 0.460222
Model Summary
S R-sq R-sq(adj) R-sq(pred)
0.0195693 88.93% 88.10% 87.03%
Table 5-35. ANOVA Table for Internal Roundness for Transformed Data
From the ANOVA Table, it seems that only the factor categorical appears to be significant.
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5.0
2.5
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SR
ES
1
Batch Day
Height Categorical
Scatterplot of SRES1 vs FITS1, Batch, Day, Height, Categorical
101
Residual Analysis
Normality
The Normality assumption for standardized residuals is yet not satisfied.
Figure 5. 57: Normality Plot of Standardized Residuals
Scatter Plot
Even after transformation, the assumption for homogeneity variance is not satisfied.
Figure 5. 58: Scatter Plot of Standardized Residuals
The assumptions for normality and homogeneity variance of standardized residuals is
not satisfied. The Analysis of Variance is quite robust towards normality and
homogeneity of variance; hence we can conclude that the factor categorical is
significant.
0.150.100.05 3.52.51.5 321
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2.5
0.0
151413
5.0
2.5
0.0
3.01.50.0
FITS2
SR
ES2
Batch Day
Height Categorical
Scatterplot of SRES2 vs FITS2, Batch, Day, Height, Categorical
102
Multiple Comparison
Tukey pairwise comparison with a confidence level of (95%) was carried out on the
categorical.
Grouping Information Using the Tukey Method and 95% Confidence
Categorical N Mean Grouping
1 36 0.174088 A
0 36 0.172587 A
2 36 0.113845 B
3 36 0.044526 C
Means that do not share a letter are significantly different.
Table 5-36. Post ANOVA of Internal Roundness vs Categorical
From the multiple comparison, we concluded that turning process had significantly
improved the internal roundness of DED 316 L stainless steel cylindrical tubes. Heat
Treatment had no impact on the internal roundness of additive manufactured DED 316
L stainless steel cylindrical tube. Wire EDM process is showing impact on the internal
roundness. This could be because after substrate removal, the origin selection was
disturbed. The internal roundness value dropped remarkably after turning. This is
because of machining process which improves the dimensional quality of the tube and
the tubes were more uniform.
103
5.1.9 Effect of Cylinder height, Heat Treatment, substrate removal, turning on
the external cylindricity of DED 316 L stainless steel cylindrical tubes
Cylindricity is a 3 dimensional tolerance that controls the overall form of a cylindrical
feature to ensure that it is round enough and straight along the its axis.
In order to analyze the effect of heat treatment, substrate removal by wire EDM and
turning, a Design of Analysis Experiments was performed on the DED 316 L stainless
steel cylinder. Since, a part of the cylinder is machined, so in the combined analysis I
considered only the portion that has been turned. The factors of interest were batch
(1,2,3,4), Day (1,2,3), Categorical Var (0: As built, 1: After Heat Treatment, 2: After
substrate removal, 3: After turning). The results obtained were:
Box Plot
From the boxplot it seems that external cylindricity after heat treatment appears to be
uniform. While substrate removal and turning generates outlier.
Figure 5. 59: Box Plot of External Cylindricity of DED 316 L stainless steel after complete process
chain
Main Effect Plot
From the main effect plot, it seems that factor Categorical Var appears to be most
significant.
Figure 5. 60: Main Effect Plot for External Cylindricity of DED 316 L after complete process chain
Exte
rnal
Cyl
indric
ity a
fter T
ur
Exte
rnal
cyl
indric
ity a
fter s
ub
Exte
rna l C
ylin
dri city
Aft
er H
T
Exte
rnal
cyl
indric
ity b
efore
HT
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
Dat
a
Boxplot of External cyl, External Cyl, External cyl, External Cyl
104
Interaction Plot
From figure 5.61, an interaction between Batch-Day, Batch and Categorical Var
appears to be significant.
Figure 5. 61: Interaction Plot for External Cylindricity of DED 316 L after complete process chain
Analysis
From the ANOVA table, it seems that none of the factor had significance on the
external cylindricity of DED 316 L stainless steel cylindrical tube.
Analysis of Variance
Source DF Adj SS Adj MS F-Value P-Value
Batch 3 0.12276 0.040919 1.46 0.239
Day 2 0.01850 0.009251 0.33 0.720
Categorical Var 3 0.13099 0.043662 1.56 0.214
Error 39 1.08941 0.027934
Total 47 1.36166
Model Summary
S R-sq R-sq(adj) R-sq(pred)
0.167134 19.99% 3.58% 0.00%
Table 5-37. ANOVA Table for External cylindricity after complete process chain
105
Residual Analysis
Normality Plot
The normality assumption for standardized residuals is not satisfied.
Figure 5. 62: Normality plot of standardized residuals
Scatter Plot
The scatter plot of standardized against fits shows a particular patter. The
standardized residuals are not inside the interval (-3,3). Moreover, the variance among
the levels do not appear to be homogenous.
Figure 5. 63: Scatter Plot of standardized residuals vs fits
Box Cox Transformation
Box Cox transformation
Rounded λ 2
Estimated λ 1.61336
95% CI for λ ( 2.71686, 0.537859)
Table 5-38. Box Cox Transformation
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FITS1
SR
ES1
Batch
Day Categorical Var
Scatterplot of SRES1 vs FITS1, Batch, Day, Categorical Var
106
ANALYSIS
From the ANOVA table, it seems that Categorical Var appears to be significant.
Analysis of Variance for Transformed Response
Source DF Adj SS Adj MS F-Value P-Value
Batch 3 10.723 3.5742 1.51 0.228
Day 2 0.929 0.4647 0.20 0.823
Categorical Var 3 29.809 9.9365 4.19 0.012
Error 39 92.588 2.3741
Total 47 134.049
Model Summary for Transformed Response
S R-sq R-sq(adj) R-sq(pred)
1.54080 30.93% 16.76% 0.00%
Table 5-39. ANOVA Table for Transformed Response
Residual Analysis
Normality
The Normality assumption of standardized residuals is satisfied.
Figure 5. 64: Normality Plot for Standardized Residuals
107
Scatter Plot
The scatter plot of standardized residuals indicates no trend. The standardized
residuals are inside the interval (-3,3). Moreover, the standardized residuals appear to
be homogeneous.
Figure 5. 65: Scatter Plot of Standardized Residuals Vs Fits
Since the assumption of normality and homogeneity variance of standardized
residuals is satisfied, I concluded that only factor Categorical var is significant.
Multiple Comparison
Tukey pairwise comparison with a confidence level of (95%) was carried out on
Categorical Var.
Grouping Information Using the Tukey Method and 95% Confidence
Categorical
Var N Mean Grouping
0 12 0.583480 A
3 12 0.551114 A
1 12 0.538778 A B
2 12 0.447463 B
Means that do not share a letter are significantly different.
Table 5-40. Multiple Comparison
From the multiple comparison, wire EDM process impacts the external cylindricity of
the DED 316 L tubes. This could be because of the stresses generated during the
wire EDM cutting process which influence the cylindricity of the tubes.
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SRES
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Batch
Day Categorical Var
Scatterplot of SRES2 vs FITS2, Batch, Day, Categorical Var
108
5.1.10 Effect of Cylinder height, Heat Treatment, substrate removal, turning on
the internal cylindricity of DED 316 L stainless steel cylindrical tubes
In order to analyze the effect of heat treatment, substrate removal by wire EDM and
turning, a Design of Analysis Experiments was performed on the DED 316 L stainless
steel cylinder. Since, a part of the cylinder is machined, so in the combined analysis I
considered only the portion that has been turned. The factors of interest were batch
(1,2,3,4), Day (1,2,3), Categorical Var (0: As built, 1: After Heat Treatment, 2: After
substrate removal, 3: After turning). The results obtained were:
Box Plot
From the boxplot it seems that internal cylindricity after heat treatment appears to be
uniform. While the turning process has generated outlier.
Figure 5. 66: Box Plot of Internal Cylindricity after completer process chain
Main Effect Plot
From the main effect plot, it seems that factor Categorical Var appears to be most
significant.
Figure 5. 67: Main Effect Plot for Internal Cylindricity after complete process chain of DED 316 L SS
Inte
rnal
Cyl
indric
ity A
fter T
ur
Inte
rnal
Cy lin
dricity
aft
er su
b
Inte
rnal
Cy lin
dricity
Afte
r HT
Inte
rna l C
ylin
dricity
Befo
re H
T
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
Data
Boxplot of Internal Cyl, Internal Cyl, Internal Cyl, Internal Cyl
109
Interaction Plot
From interaction plot, an interaction between Batch-Day, Batch and Categorical Var
appears to be significant. But since Batch and Day are blocking factors, the interaction
cannot be evaluated.
Figure 5. 68: Interaction Plot for Internal Cylindricity after complete process chain of DED 316 L SS
Analysis
From the ANOVA table, it seems that Categorical Var appears to be significant.
Analysis of Variance
Source DF Adj SS Adj MS F-Value P-Value
Batch 3 0.13408 0.04469 1.05 0.382
Day 2 0.02361 0.01180 0.28 0.760
Categorical Var 3 0.39095 0.13032 3.06 0.039
Error 39 1.66214 0.04262
Total 47 2.21078
Model Summary
S R-sq R-sq(adj) R-sq(pred)
0.206444 24.82% 9.39% 0.00%
Table 5-41. ANOVA for Internal Cylindricity
110
Residual Analysis
Normality Plot
The normality assumption for standardized residuals is not satisfied.
Figure 5. 69: Normality Plot of Standardized Residuals
Scatter Plot
The scatter plot of standardized residuals indicates no trend. The standardized
residuals appear to be inside the interval (-3,3). Moreover, the homogeneity of
variance seems to be satisfied.
Figure 5. 70: Scatter Plot of standardized residuals
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-1
3210
FITS1
SR
ES1
Batch
Day Categorical Var
Scatterplot of SRES1 vs FITS1, Batch, Day, Categorical Var
111
Box Cox Transformation
Box-Cox transformation
Rounded λ -1
Estimated λ -1.4039
95% CI for λ (-2.33640, -0.479397)
Table 5-42. Box Cox Transformation
ANALYSIS
From the ANOVA table, it seems that the factor Categorical Var appears to be
significant.
Analysis of Variance for Transformed Response
Source DF Adj SS Adj MS F-Value P-Value
Batch 3 0.7520 0.25067 1.06 0.379
Day 2 0.1014 0.05068 0.21 0.809
Categorical Var 3 3.8723 1.29076 5.43 0.003
Error 39 9.2651 0.23757
Total 47 13.9907
Model Summary for Transformed Response
S R-sq R-sq(adj) R-sq(pred)
0.487407 33.78% 20.19% 0.00%
Table 5-43. ANOVA Table for Internal Cylindricity
Residual Analysis
Normality Plot
Even after box cox transformation, the normality assumption for standardized
residuals is not satisfied.
Figure 5. 71: Normality Plot of Standardized Residuals
112
Scatter Plot
The scatter plot of standardized residuals indicates no trend. The standardized
residuals appear to be inside the interval (-3,3). Moreover, the homogeneity of
variance seems to be satisfied.
Figure 5. 72: Scatter Plot of Standardized Residuals
Since the assumption of homogeneity variance is satisfied, and Minitab is quite robust
towards normality assumption of standardized residuals, we concluded that
Categorical Var is the significant factor.
Multiple Comparison
Tukey pairwise comparison with a confidence level of (95%) was carried out. From the
multiple comparison, I concluded that impact of internal turning is significantly different
on the internal cylindricity of DED 316 L stainless steel cylindrical tubes.
Grouping Information Using the Tukey Method and 95% Confidence
Categorical
Var N Mean Grouping
0 12 0.653597 A
1 12 0.599970 A
2 12 0.533665 A B
3 12 0.438196 B
Means that do not share a letter are significantly different.
Table 5-44. Post ANOVA for Internal Cylindricity
From the multiple comparison, wire EDM process impacts the internal cylindricity of
the DED 316 L tubes. This could be because of the stresses generated during the
wire EDM cutting process which influence the cylindricity of the tubes.
-1.50-1.75-2.00-2.25-2.50 4321
3
2
1
0
-1
3.02.52.01.51.0
3
2
1
0
-1
3210
FITS2
SR
ES
2
Batch
Day Categorical Var
Scatterplot of SRES2 vs FITS2, Batch, Day, Categorical Var
113
ROUGHNESS RESULTS
5.2.1Effect of Position, orientation, internal and external surface on the
roughness of DED 316 L cylindrical tube before Heat Treatment
A multiway ANOVA was performed to determine the effect of position i.e. (1: close to
the substrate, 2: at the middle and 3: at the edge); orientation and external/ internal
surface on the roughness of additive manufactured DED 316 L stainless steel
cylindrical tubes. The factor of interest were position (1: close to the substrate, 2: at
the middle, 3: at the edge), orientation (1,2,3,4), external/internal (0: External surface,
1: internal surface), as shown in figure 119 blocking factors order in batch (1,2,3,4)
and Day (1,2,3). The results obtained were:
Figure 5. 73: Schematic of Position, orientation and External/Internal Data Snooping
Individual Value Plot
From the individual value plot, it seems that External/internal part appears to be
significant. The factor position i.e. position 1 close to the substrate appears significant
before heat treatment for the External and not for the internal.
Figure 5. 74: Individual Value Plot for Roughness before Heat Treatment
External / internal part
orientation
position
10
43214321
321321321321321321321321
22.5
20.0
17.5
15.0
12.5
10.0
7.5
5.0
Ro
ug
hn
ess
befo
re H
T
Individual Value Plot of Roughness before HT
114
Main Effect Plot
From the main effect plot, it seems that the factor external/internal part, position seems
to be significant while, day and order in batch have no effect and we neglect them in
the analysis.
Figure 5. 75: Main Effect pot for Roughness before Heat Treatment
Interaction Plot
Figure 5. 76: Interaction Plot for Roughness before Heat Treatment From the interaction plot, interaction seems to be present between position-
orientation.
115
ANALYSIS
Analysis of Variance
Source DF Adj SS Adj MS F-Value P-Value
position 2 55.86 27.928 5.57 0.004
orientation 3 30.43 10.142 2.02 0.111
External / internal part 1 823.77 823.774 164.26 0.000
position*orientation 6 16.45 2.741 0.55 0.772
position*External / internal part 2 28.87 14.433 2.88 0.058
orientation*External / internal part 3 26.30 8.765 1.75 0.158
position*orientation*External / internal part6 44.95 7.492 1.49 0.180
Error 264 1323.97 5.015
Total 287 2350.59
Model Summary
S R-sq R-sq(adj) R-sq(pred)
2.23943 43.68% 38.77% 32.97%
Table 5-45. ANOVA Table for Roughness before Heat Treatment
The normality and homogeneity of variance assumption for standardized residuals
was satisfied. Therefore, the factor position, and External/ internal part significantly
effect the roughness of DED 316 L stainless steel tube.
5.2.2 Effect of Position, orientation, internal and external surface on the
roughness of DED 316 L cylindrical tube after Heat Treatment
In order to analyze the impact of position, orientation, internal and external part on the
surface roughness of additive manufactured DED 316 L stainless steel cylindrical
tubes after heat treatment, a design of analysis experiment was conducted. The factor
of interest were position (1: close to the substrate, 2: at the middle, 3: at the edge),
orientation (1,2,3,4), external/internal (0: External surface, 1: internal surface),
blocking factors order in batch (1,2,3,4) and Day (1,2,3). The results obtained were:
Data Snooping
Individual Value Plot
From the individual value plot, it seems that the factor External/internal appears to be
significant. The roughness value for internal surface of the DED 316 L tubes seems to
be higher than the external roughness. The higher roughness on internal surface is
related to the presence of sinterized particles in higher amount. The factor position
seems to have impact on the Roughness after heat treatment. The position 1 which is
close to the substrate seems to be different from position 2 and 3 because of the
uncontrolled growing of the layers at the beginning of the process.
116
Figure 5. 77: Individual Value plot for Mean Roughness after Heat Treatment
Main Effect Plot
From the main effect plot, it seems that the factors External/ Internal, position are
significant while Day and order in batch had no effect and can be neglected. This
means that the mean roughness seems to be different for the external/ internal surface
of the tubes and since the factor position seems significant, it indicates that the mean
roughness is varying along the length of the tube. While since the blocking factor Day
is not significant, it means that the tubes produced in different days have similar
roughness.
Figure 5. 78: Main effect Plot for Roughness after Heat Treatment
External/Internal
orientation
position
10
43214321
321321321321321321321321
17.5
15.0
12.5
10.0
7.5
5.0
Ro
ug
hn
ess
afte
r H
TIndividual Value Plot of Roughness after HT
117
5.2.3 Effect of position, internal / external part and heat treatment on the mean
roughness
In order to analyze the impact of position, internal/external part and heat treatment on
the mean roughness of a particular position calculated by considering different
orientations, a design of analysis experiment was conducted. The factor of interest
were position (1: close to the substrate, 2: at the middle, 3 at the edge),
external/internal (0: external surface ; 1 internal surface) and heat treatment (0: before
heat treatment, 1: After Heat treatment) and the response variable is the mean
roughness calculated for various positions considering the different orientations. The
results are:
Data Snooping
Individual Value plot
From the individual value plot, it seems that the factor External/ internal and Position
seems to be significant.
Figure 5. 79: Individual value plot of Mean Roughness
External / internal
Heat Treatment
Position
10
1010
321321321321
16
14
12
10
8
6
Mea
n R
ough
ness
Individual Value Plot of Mean Roughness
118
Main Effect Plot
From the main effect plot, it seems that the factor External/ internal, Heat Treatment
and Position appear to be significant. While Day and order of Batch can be neglected.
The mean roughness for position 1, which is close to the substrate is significantly
different from position 2 and position 3 which is at the middle and at the edge of
additive manufactured DED 316 L stainless steel cylindrical tubes. This is because of
the uncontrolled growing of the layers at the beginning of the tube, which then
stabilizes afterwards to a layer thickness of 0.2 mm
Figure 5. 80: Main Effect Plot for Mean Roughness
119
5.2.4 Effect of Heat Treatment and External/ internal factors on the mean
roughness of each specimen in terms of position and orientation
In order to analyze the effect of heat treatment and External/ internal factor on the
mean roughness of each specimen in terms of position and orientation, a design of
analysis experiment was conducted. The factors of interest were Heat Treatment (0:
Before Heat Treatment, 1: After Heat Treatment), External/internal (0: External
surface, 1: Internal surface) and the result was the mean roughness of each specimen
in terms of position and orientation. The results are detailed as:
Data Snooping
Individual Value Plot
From the individual value plot, External/Internal seems to be really significant and also
heat treatment seems to be significant.
Figure 5. 81: Individual Value Plot of Mean Roughness
External/Internal
Heat Treatment
10
1010
15
14
13
12
11
10
9
8
Mean
Ro
ug
hn
ess
Individual Value Plot of Mean Roughness
120
Main Effect Plot
From the main effect plot, it seems that the factor External/Internal and Heat Treatment
appear significant. While Day and order of batch can be neglected.
Figure 5. 82: Main Effect Plot for Mean Roughness
Interaction Plot
From the interaction plot, there seems to be no interaction between
External/internal*Heat Treatment.
Figure 5. 83: Interaction Plot for Mean Roughness
121
ANALYSIS
From the ANOVA table, it seems that External/Internal and Heat Treatment are
significant factors.
Analysis of Variance
Source DF Adj SS Adj MS F-Value P-Value
External/Internal 1 128.432 128.432 242.31 0.000
Heat Treatment 1 11.657 11.657 21.99 0.000
External/Internal*Heat Treatment 1 0.292 0.292 0.55 0.462
Error 44 23.322 0.530
Total 47 163.703
Model Summary
S R-sq R-sq(adj) R-sq(pred)
0.728038 85.75% 84.78% 83.05%
Table 5-46. ANOVA Table for Mean Roughness
Residual Analysis
Normality Plot
The p value for normality test is 0.663 which is higher than the significance level (5%).
Therefore, the normality assumption for standardized residuals is satisfied.
Figure 5. 84: Normality Plot for Standardized Residuals
122
Scatter Plot
The scatter plot of standardized residuals vs fits indicate no pattern. The standardized
residuals are inside the interval (-3,3). There appear no outlier and the homogeneity
of variance of standardized residuals is satisfied.
Figure 5. 85: Scatter Plot of Standardized Residuals vs fits
Since the assumption for normality and homogeneity variance of standardized
residuals is satisfied, we conclude that the factor Heat Treatment, External/Internal
are significant factors.
Multiple Comparison
Tukey pairwise comparison with a confidence level of (97.5%) was carried out on Heat
Treatment and External/Internal. The results are detailed as:
From the multiple comparison table, it is clear that External/internal is significant. From
the Multiple comparison table, we see that roughness values for internal surface of
DED 316 L stainless steel cylindrical tubes is higher than the external roughness of
additive manufactured DED 316 L stainless steel tubes. The higher roughness for
internal surfaces of the tubes is related to the presence of sinterized particles in higher
amount. On the internal surfaces of the additive manufactured DED 316 L stainless
steel cylindrical tubes, there is high probability of sinterized powders which can be
easily attached to the walls due to the bouncing of non-melted particles
Grouping Information Using the Tukey Method and 97.5% Confidence
External/Internal N Mean Grouping
1 24 13.1533 A
0 24 9.8818 B
Means that do not share a letter are significantly different.
Table 5-47. POST ANOVA for Mean Roughness Vs Position
1413121110 1.000.750.500.250.00
2
1
0
-1
-2
1.000.750.500.250.00
2
1
0
-1
-2
FITS1
SR
ES1
External/Internal
Heat Treatment
Scatterplot of SRES1 vs FITS1, External/Internal, Heat Treatment
123
From the multiple comparison, we conclude that heat treatment had significant impact
on the mean roughness of additive manufactured DED 316 L stainless steel cylindrical
tube. The roughness of additive manufactured DED 316 L stainless steel cylindrical
tube after heat treatment is less than the roughness values before heat treatment. This
can be because of the stress relief effect that can cause detachment of the sinterized
particle and results in the improvement in the roughness of additive manufactured
DED 316 L stainless steel cylindrical tubes.
Grouping Information Using the Tukey Method and 97.5% Confidence
Heat
Treatment N Mean Grouping
0 24 12.0103 A
1 24 11.0247 B
Means that do not share a letter are significantly different.
Table 5-48. POST ANOVA for Mean Roughness Vs Heat Treatment
124
5.2.5 Effect of Heat Treatment on The External Roughness of DED 316 L
stainless Steel tubes
From the graphical analysis, we conclude that Heat Treatment had significantly
improved the external roughness of DED 316 L stainless steel tubes since both the
mean value and the standard deviation of external roughness had reduced after heat
treatment. This is attributed to the stress relief effect that can cause detachment of
the sinterized particles.
Figure 5. 86 : Effect of Heat Treatment on the Mean External Roughness (RA)
Figure 5. 87: Effect of Heat Treatment on the Standard Deviation of External Roughness (RA)
0
2
4
6
8
10
12
14
1 2 3 4 5 6 7 8 9 10 11 12
Me
an E
xte
rnal
Ro
ugh
ne
ss (
µm
)
Specimen
Mean External Roughness before and after Heat Treatment
RA before HT RA After HT
0
0.2
0.4
0.6
0.8
1
1.2
1 2 3 4 5 6 7 8 9 10 11 12
Stan
dar
d D
evi
atio
n o
f R
a
Specimen
Standard Deviation of External Roughness before and after Heat Treatment
STD Ra BF HT STD RA Af HT
125
5.2.6 Effect of Heat Treatment on the Internal Roughness of DED 316 L
stainless steel tubes
From the graphical analysis, we conclude that Heat Treatment had significantly
improved the internal roughness of DED 316 L stainless steel tubes since both the
mean value and the standard deviation of internal roughness had reduced after heat
treatment. This is attributed to the stress relief effect that can cause detachment of
the sinterized particles.
Figure 5. 88: Effect of Heat Treatment on the Mean value of Internal Roughness (RA)
Figure 5. 89 : Effect of Heat Treatment on the Standard Deviation of Internal Roughness (RA)
0
2
4
6
8
10
12
14
16
1 2 3 4 5 6 7 8 9 10 11 12Me
an In
tern
al R
ou
ghn
ess
(µ
m)
Specimen
Mean Internal Roughness before and After Heat Treatment
RA Before HT RA After Ht
0
0.5
1
1.5
2
2.5
3
1 2 3 4 5 6 7 8 9 10 11 12
Stan
dar
d D
evi
atio
n o
f R
a
Specimen
Standard Deviation of Internal Roughness before and after Heat Treatment
STD RA bf HT STD RA AF HT
126
5.2.7: Effect of cutting speed and feed rate on the External Roughness
During machining, cutting speed and feed rate seems to impact surface roughness.
From figure 5.90, we see that the surface roughness decreases with the increase in
the cutting speed for DED 316 L tubes. This is because by increasing the cutting
speed, the material gets softer because of adiabatic heating and friction at the tool
chip interface and it reduces the adhered material on the tool rake interface.
Figure 5. 90: External Roughness after machining of DED 316 L at various cutting speed of (27 m/min) and (54 m/min) and feed rate (0.07mm/rev) and (0.14 mm/rev)
From the results of our analysis as shown in figure 5.90, it is found out that external
roughness of DED 316 L tubes increases with the increase in the feed rate. The
increase in surface roughness with the increase in tool wear could be attributed to tool
vibration and thermal softening.
ANALYSIS OF VARIANCE
In order to find out the impact of cutting speed and feed rate on the surface roughness,
a Design of Analysis experiment was carried out with 2 levels of cutting speed (27
m/min and 54 m/min), 2 levels of feed rate (0.07 mm/rev and 0.14 mm/rev). The
experiment was replicated three times and considering the day as blocking factor. The
results were as:
0
0.5
1
1.5
2
2.5
3
3.5
4
27 54
Surf
ace
Ro
ugh
nes
s (µ
m)
Cutting speed (m/min)
Effect of Cutting speed and feed Rate on External Roughness
feed rate(0.07mm/rev)
127
Data Snooping
Main Effect Plot
From the main effect plot, it seems that feed rate has major impact on the external
roughness of DED 316 L tubes subjected to machining operation.
Figure 5. 91: Main effect plot of External roughness Vs cutting speed and feed rate
Interaction Plot
From the interaction plot, there seems to be no interaction between cutting speed and
feed rate.
Figure 5. 92: Interaction plot of External Roughness vs cutting speed and feed rate
128
ANALYSIS
Analysis of Variance
Source DF Adj SS Adj MS F-Value P-Value
Model 5 19.4658 3.8932 162.72 0.000
Blocks 2 0.0813 0.0407 1.70 0.260
Linear 2 19.3291 9.6646 403.94 0.000
cutting speed 1 0.0441 0.0441 1.84 0.223
feed rate 1 19.2850 19.2850 806.03 0.000
2-Way Interactions 1 0.0554 0.0554 2.31 0.179
cutting speed*feed rate 1 0.0554 0.0554 2.31 0.179
Error 6 0.1436 0.0239
Total 11 19.6093
Model Summary
S R-sq R-sq(adj) R-sq(pred)
0.154680 99.27% 98.66% 97.07%
Table 5-49. ANOVA Table of External Roughness From the ANOVA table, we found out that the feed rate is the only significant factor as
its p value was less than the significance level (5 %), while cutting speed and blocking
factors appears to have no impact on the external roughness of DED 316 L tubes.
Residual Analysis
Normality
The p value for normality test was 0.948 which was much higher than significance
level of (5 %). Therefore, the normality assumption was satisfied.
Figure 5. 93: Normality plot for Standardized Residuals
129
Scatter plot
The scatter plot of standardized residuals vs fits indicates no particular pattern. The
standardized residuals are inside the interval (-3,3) and the homogeneity of variance
seems to be ok
Figure 5. 94: Scatter plot of Standardized Residuals vs Fits
Test for Equal Variance
Method
Null hypothesis All variances are equal
Alternative hypothesis At least one variance is different
Significance level α = 0.05
95% Bonferroni Confidence Intervals for Standard Deviations
cutting feed
speed rate N StDev CI
-1 -1 3 0.73775 (0.0028225, 1151.74)
-1 1 3 0.74439 (0.0028478, 1162.09)
1 -1 3 1.49914 (0.0057354, 2340.38)
1 1 3 1.62917 (0.0062328, 2543.37)
Individual confidence level = 98.75%
Tests
Test
Method Statistic P-Value
Multiple comparisons — 0.666
Levene 0.51 0.686
Table 5-50. Test for Equal Variance
Multiple comparison
4321 1.00.50.0-0.5-1.0
2
1
0
-1
-2
1.00.50.0-0.5-1.0
2
1
0
-1
-2
FITS1
SR
ES1
cutting speed
feed rate
Scatterplot of SRES1 vs FITS1, cutting speed, feed rate
130
Tukey Pairwise Comparisons: Response = External Roughness, Term = feed rate
Tukey pairwise comparison with confidence level of (95 %) was carried out on the
feed rate.
Grouping Information Using the Tukey Method and 95% Confidence
Feed
rate N Mean Grouping
1 6 3.75063 A
-1 6 1.21521 B
Means that do not share a letter are significantly different
Table 5-51. POST ANOVA of External Roughness vs feed rate
CONCLUSION
Since the residual assumption of homogeneity variance is satisfied. The p value for
levene’s test is 0.686, which is higher than significance level (5 %) , therefore
assumption for equal variance is satisfied. Moreover, the normality assumption was
also satisfied. We conclude that only feed rate is the significant factor which impacts
the external roughness of additive manufactured 316 L stainless steel tube.
The multiple comparison results confirmed our previous results, that by increasing the
feed rate surface roughness increases for additive manufactured DED 316 L tubes.
The results found were in accordance with the study carried out on the machinability
of additive manufactured components as discussed in the state of the art.
131
5.2.8 Effect of cutting speed and feed rate on the Internal Roughness
During machining, cutting speed and feed rate seems to affect internal roughness.
From figure 5.95, we see that the internal roughness decreases with the increase in
the cutting speed for additive manufactured DED 316 L tubes. This is because by
increasing the cutting speed, the material gets softer because of adiabatic heating and
friction at the tool chip interface and it reduces the adhered material on the tool rake
interface.
Figure 5. 95: Internal Roughness after machining of DED 316 L at various cutting speed of (27 m/min) and (54 m/min) and feed rate (0.07mm/rev) and (0.14 mm/rev)
ANALYSIS OF VARIANCE
In order to find out the impact of cutting speed and feed rate on the surface roughness,
a Design of Analysis experiment was carried out with 2 levels of cutting speed (27
m/min and 54 m/min), 2 levels of feed rate (0.07 mm/rev and 0.14 mm/rev). The
experiment was replicated three times and considering the day as blocking factor. The
results were as:
Data Snooping
Main Effect plot
From the main effect plot, it seems that feed rate has major influence on the internal
roughness of DED 316 L stainless steel tubes subjected to machining operation.
Figure 5. 96: Main effect plot of internal roughness
0
1
2
3
4
27 54
Surf
ace
Ro
ugh
nes
s (µ
m)
cutting speed (m/min)
Effect of cutting speed and feed rate on internal Roughness
feed rate(0.07mm/rev)
132
Interaction Plot
From the interaction plot, there seems to be no interaction between cutting speed and
feed rate.
Figure 5. 97: Interaction plot of Internal Roughness
Analysis
Analysis of Variance
Source DF Adj SS Adj MS F-Value P-Value
Model 5 11.1227 2.2245 7.10 0.017
Blocks 2 1.0522 0.5261 1.68 0.264
Linear 2 9.8548 4.9274 15.73 0.004
cutting speed 1 1.3308 1.3308 4.25 0.085
feed rate 1 8.5240 8.5240 27.21 0.002
2-Way Interactions 1 0.2157 0.2157 0.69 0.438
cutting speed*feed rate 1 0.2157 0.2157 0.69 0.438
Error 6 1.8798 0.3133
Total 11 13.0025
Model Summary
S R-sq R-sq(adj) R-sq(pred)
0.559733 85.54% 73.50% 42.17%
Table 5-52. ANOVA Table for Internal Roughness
From the ANOVA table, we found out that it is the feed rate that has p value which
was significantly less than significance level of (5 %). Cutting speed and blocking
factor appears to be non-significant.
133
Residual Analysis
Normality
The p value of normality test is 0.712, which is significantly higher than significance
level of (5 %). Therefore, the normality assumption for standardized residuals was ok.
Figure 5. 98: Normality plot of Standardized Residuals
Scatter Plot
The scatter plot of standardized residuals vs fits indicates no particular pattern. The
standardized residuals are inside the interval (-3,3) and the homogeneity of variance
seems to be ok
Figure 5. 99: Scatter plot of Standardized residuals vs fits
4321 1.00.50.0-0.5-1.0
2
1
0
-1
-2
1.00.50.0-0.5-1.0
2
1
0
-1
-2
FITS1
SR
ES1
cutting speed
feed rate
Scatterplot of SRES1 vs FITS1, cutting speed, feed rate
134
Test for Equal Variance
Method
Null hypothesis All variances are equal
Alternative hypothesis At least one variance is different
Significance level α = 0.05
95% Bonferroni Confidence Intervals for Standard Deviations
Cutting feed
speed rate N StDev CI
-1 -1 3 1.03173 (0.0039472, 1610.69)
-1 1 3 0.51234 (0.0019601, 799.84)
1 -1 3 1.94294 (0.0074333, 3033.22)
1 1 3 0.94763 (0.0036254, 1479.40)
Individual confidence level = 98.75%
Tests
Test
Method Statistic P-Value
Multiple comparisons — 0.352
Levene 0.51 0.688
Table 5-53. Test for Equal Variance
Multiple Comparison
Tukey pairwise comparison with confidence level of (95 %) was carried out on the
feed rate.
Tukey Pairwise Comparisons: Response = Internal Roughness, Term = feed rate
Grouping Information Using the Tukey Method and 95% Confidence
Feed
rate N Mean Grouping
1 6 3.43979 A
-1 6 1.75417 B
Means that do not share a letter are significantly different.
Table 5-54. Post ANOVA Analysis of Internal Roughness vs feed rate
Since the residual assumption of homogeneity variance is satisfied. The p value for
levene’s test is 0.688, which is higher than significance level (5 %), therefore
assumption for equal variance is satisfied. Moreover, the normality assumption was
also satisfied. We conclude that only feed rate is the significant factor which impacts
the internal roughness of additive manufactured 316 L stainless steel tube.
The multiple comparison results confirmed our previous results, that by increasing the
feed rate surface roughness increases for additive manufactured DED 316 L tubes.
135
RESULTS
5.3 MICRO HARDNESS
5.3.1 Effect of position and Heat Treatment on the Micro Hardness of Specimen
A Multiway Design of Analysis Experiment was performed to determine the effect of
position and heat treatment on the micro hardness of additive manufactured DED 316
L stainless steel cylindrical tubes. The factors chosen include specimen (1,2,3),
Position (1: close to substrate; 2 in the middle; 3 at the top of cylindrical tube) and Heat
Treatment (0: before Heat Treatment; 1 After Heat Treatment). The results obtained
were:
Data Snooping
Individual Value Plot
The individual value plot indicates that microhardness at position 1 which is close to the substrate is significantly different from microhardness at the middle and at the edge of DED 316 L stainless steel tube . This is because of the uncontrolled growing of the layers at the beginning of the DED process and the thermal phenomenon i.e. rapid cooling that occurs close to the first deposition layer which alters the microstructure close to the substrate to be different from the middle and close to the edge of additive manufactured DED 316 L stainless steel cylindrical tubes.
Figure 5. 100: Individual Value Plot of Mean Hardness vs Position and Heat Treatment
Heat Treatment
Position
10
321321
205
200
195
190
185
180
175
170
Mean
Hard
ness
Individual Value Plot of Mean Hardness
136
Main Effect Plot
From the main effect plot, it seems that the factor “Position” seems to be significant.
Figure 5. 101: Main Effect Plot for Mean Hardness vs Specimen, Position, Heat Treatment
Interaction Plot
From the interaction plot, interaction seems to be present between specimen-heat
treatment and Position-Heat Treatment.
Figure 5. 102: Interaction Plot for Mean Hardness vs specimen, Position, Heat Treatment
137
ANALYSIS
From ANOVA table, the p value for the factor “Position” is less than the significance
level of (5%). Therefore, it seems that the factor position appears to be significant.
Analysis of Variance
Source DF Adj SS Adj MS F-Value P-Value
Specimen 2 3.80 1.900 0.07 0.932
Position 2 1311.21 655.603 24.60 0.000
Heat Treatment 1 6.25 6.246 0.23 0.637
Error 12 319.84 26.653
Total 17 1641.09
Model Summary
S R-sq R-sq(adj) R-sq(pred)
5.16269 80.51% 72.39% 56.15%
Table 5-55. ANOVA Table for Mean Hardness
Residual Analysis
Normality Plot
The p value for normality plot is 0.802 which is higher than significance level of (5%).
Therefore, the normality assumption for standardized residuals is satisfied.
Figure 5. 103: Normality Plot for Standardized Residuals
138
Scatter Plot
The scatter plot of standardized residuals vs fits indicates no trend. The standardized
residuals are inside the interval (-3,3). There appear no outliers and the homogeneity
of variance seems to be satisfied.
Figure 5. 104: Scatter Plot of Standardized Residuals vs Fits
Since the assumption for normality and homogeneity variance of standardized
residuals is satisfied, we concluded that the factor position is significant factor.
Multiple Comparison
Tukey pairwise comparison with a confidence level of (95%) was carried out on
Position. The results are detailed as:
Grouping Information Using the Tukey Method and 95% Confidence
Position N Mean Grouping
1 6 190.738 A
3 6 175.083 B
2 6 170.911 B
Means that do not share a letter are significantly different.
Table 5-56. Post ANOVA table for Mean Hardness
CONCLUSION
From the multiple comparison, we conclude that the microhardness at Position 1 which
is close to the substrate is significantly different from the microhardness at position 2
and 3 which are at the middle and close to the edge of additive manufactured DED
316 L stainless steel cylindrical tubes. This is because of the uncontrolled growing of
the layers at the beginning of the process and the thermal phenomena i.e. rapid
cooling that occurs close to the first deposition layer which alters the microstructure
close to the substrate to be different from the middle and close to the edge of additive
manufactured DED 316 L stainless steel cylindrical tube.
190185180175170 3.02.52.01.51.0
2
1
0
-1
-2
3.02.52.01.51.0
2
1
0
-1
-2
1.000.750.500.250.00
FITS1
SR
ES1
Specimen
Position Heat Treatment
Scatterplot of SRES1 vs FITS1, Specimen, Position, Heat Treatment
139
5.3.2 Effect of cutting speed and feed rate on the micro hardness of DED 316 L
cylindrical tubes
In order to analyze the impact of cutting speed and feed rate on the micro hardness of
DED 316 L, a Design of Analysis experiment was conducted, with 2 levels of cutting
speed (27m/min; 54 m/min) and two levels of feed rate (0.07 mm/rev; 0.14 mm/rev).
Each experimental condition was replicated 3 times. The results obtained were:
Data Snooping
Individual Value Plot
From the individual value plot, it seems that feed rate has major impact on the
hardness of DED 316 L. There seems to be an interaction between cutting speed and
feed rate.
Figure 5. 105: Individual value plot of Hardness
cutting speed
feed rate
1-1
1-11-1
185
180
175
170
165
160
155
Hard
ness
Individual Value Plot of Hardness
140
Main Effect plot
From the main effect plot, it seems that feed rate has major impact on the micro
hardness of DED 316 L cylindrical tubes.
Figure 5. 106: Main Effect Plot for Hardness
Interaction Plot
From the interaction plot, since the lines between cutting speed and feed rate are non-
parallel, it indicates that there might be an interaction between cutting speed and feed
rate
Figure 5. 107: Interaction Plot for Hardness
141
ANALYSIS
Analysis of Variance
Source DF Adj SS Adj MS F-Value P-Value
Model 5 894.47 178.894 27.34 0.000
Blocks 2 41.48 20.739 3.17 0.115
Linear 2 668.91 334.454 51.12 0.000
cutting speed 1 40.09 40.089 6.13 0.048
feed rate 1 628.82 628.818 96.12 0.000
2-Way Interactions 1 184.08 184.083 28.14 0.002
cutting speed*feed rate 1 184.08 184.083 28.14 0.002
Error 6 39.25 6.542
Total 11 933.72
Model Summary
S R-sq R-sq(adj) R-sq(pred)
2.55777 95.80% 92.29% 83.18%
Table 5-57. ANOVA Table for Hardness
By applying Bonferroni approach, the p value of feed rate and interaction between
cutting speed and feed rate is less than the significance level and they seems to be
significant.
Residual Analysis
Normality Plot
The p value of Normality test is 0.567 which is higher than the significance level of
(5%). Therefore, the assumption for normality of standardized residuals is satisfied.
Figure 5. 108: Normality Plot of Standardized Residuals
142
Scatter Plot
The scatter plot of standardized residuals vs fits indicates no pattern. The standardized
residuals are inside the interval (-3,3) and the homogeneity of variance seems to be
ok.
Figure 5. 109: Scatter Plot of Standardized Residuals Vs Fits
Since the assumption for normality and homogenous variance of standardized residuals is satisfied, we concluded that feed rate and interaction between cutting speed and feed rate had an impact on the micro hardness of DED 316 L stainless steel cylindrical tubes.
POST ANOVA Analysis Tukey Pairwise Comparisons: Response = Hardness, Term = cutting speed*feed rate A Tukey pairwise comparison with confidence level of 95 % was carried out on the
interaction between cutting speed and feed rate. The results were:
Grouping Information Using the Tukey Method and 95% Confidence
Cutting
speed*feed
rate N Mean Grouping
1 1 3 180.756 A
-1 1 3 169.267 B
-1 -1 3 162.622 B C
1 -1 3 158.444 C
Means that do not share a letter are significantly different.
Table 5-58. POST ANOVA Analysis of (Cutting speed * feed rate) on the Micro Hardness of DED 316 L stainless steel tubes
180170160 1.00.50.0-0.5-1.0
2
1
0
-1
-2
1.00.50.0-0.5-1.0
2
1
0
-1
-2
FITS1
SR
ES1
cutting speed
feed rate
Scatterplot of SRES1 vs FITS1, cutting speed, feed rate
143
6 CONCLUSION AND FINAL RECOMMENDATIONS
This work conducted a complete process chain study on the additive manufactured
DED 316 L stainless steel cylindrical tubes. The dimensional characteristics, surface
roughness, and hardness testing was done for the as built, heat treated and machined
DED 316 L stainless steel cylindrical tubes. The following conclusions can be drawn
from this study:
1: The DED 316 L stainless steel tubes fabricated were assumed to be perfect
cylinders and it was assumed that there is no variation in the dimensional
characteristic along the length of the tubes. The results reveal that the external and
internal diameter of DED 316 L cylindrical tubes were varying along the length of
cylindrical tubes. This indicates that the tubes produced were not perfect cylinders and
there is some conicity in the tubes.
2: Heat Treatment had significantly improved the dimensional quality of the additive
manufactured DED 316 L stainless steel cylindrical tubes as the external and internal
roundness values dropped. This is associated to the stress releasing effect due to heat
treatment and the removal of excessive powder materials attached to the DED 316 L
stainless steel cylindrical tubes.
3: The roughness value for the internal surfaces of additive manufactured DED 316 L
stainless steel cylindrical tubes is higher than the external roughness of DED 316 L
stainless steel cylindrical tubes. The higher roughness of the internal surfaces is
related to the presence of sinterized particles in higher amount. On the internal surface
of additive manufactured DED 316 L stainless steel cylindrical tubes, there is high
probability of sinterized powders which can be easily attached to the walls due to the
bouncing of non-melted particles.
4: The surface roughness of additive manufactured DED 316 L stainless steel
cylindrical tubes were different at the position close to the substrate as compared to
the roughness at the middle and at the end of DED 316 L cylindrical tubes. A possible
reason for this is the uncontrolled growing of the layers at the beginning of the process
and afterwards, the process is stable to follow layer thickness of 0.2mm.
5: Heat treatment process improved the surface quality of additive manufactured DED
316 L stainless steel cylindrical tubes. The surface roughness (RA) reduced from an
average value of 11.5 µm to about 9.8 µm. This is attributed to the stress relief effect
that can cause detachment of the sinterized particles and results in the improvement
in the roughness of additive manufactured DED 316 L stainless steel cylindrical tubes.
6: The finish machining process substantially reduces the surface roughness (RA),
and thus enhances the surface quality of additive manufactured DED 316 L stainless
steel cylindrical tubes. The cutting speed had a slight impact on the surface roughness
that is not proved by ANOVA result. The roughness value decreases with the increase
in the cutting speed. The results of surface roughness with the cutting speed were
aligned with the results of previous studies. This is because as the cutting speed
144
increases, the material gets softer because of adiabatic and friction heating at the tool
chip interface which reduces the adhered material on the tool rake interface. In the
past, it was found out that feed rate had major impact on the surface roughness. This
is confirmed by the ANOVA results of my study that the feed rate had a major influence
on the surface roughness of additive manufactured DED 316 L tubes.The surface
roughness of additive manufactured DED 316 L stainless steel cylindrical tubes
increases with the increase in the feed rate. The increase in the roughness with feed
rate is associated to the tool vibration and thermal softening.
7: The microhardness of additive manufactured DED 316 L stainless steel cylindrical
tubes varies with the position. The microhardness at position close to the substrate
was different from the microhardness at the middle and at the edge of cylindrical tubes.
This is because of uncontrolled growing of the layers at the beginning of the DED
process and the thermal phenomena i.e. rapid cooling that occurs close to the first
deposition layer which alters the microstructure close to the substrate to be different
from the middle and close to the edge of additive manufactured DED 316 L stainless
steel cylindrical tubes.
8: Heat treatment had a little impact on the microhardness of additive manufactured
DED 316 L tubes. In particular, the microhardness values reduced from an average
value of 180.12 to 178.32
9: The finish machining process had significant impact on the microhardness of
additive manufactured DED 316 L stainless steel cylindrical tube. The microhardness
of DED 316 L tubes increases with the increase in feed rate. The interaction between
cutting speed and feed rate was found to be significant. The microhardness of DED
316 L stainless steel was higher at high level of feed rate and it was even better with
increase in the cutting speed.
145
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148
APPENDIX 1 HARDNESS RESULTS
Specimen Position
M1 M1 M1 M2 M2 M2 M3 M3 M3
1 192.6 196.7 197.2 172.1 168.5 168.8 170.1 179.7 174
2 201.4 202 203.2 172.8 173.8 173 164.1 174.6 175.3
3 192.9 182.6 180.1 169.8 175.6 157.1 171.6 177.3 179.7
Hardness Before Heat Treatment
Specimen Position
M1 M1 M1 M2 M2 M2 M3 M3 M3
1 186 186.1 186.5 156 189.1 168.8 184.2 176 174.1
2 183.5 178.7 185.7 173.8 162.6 173 178.5 175.4 175
3 197.3 188.3 192.5 169.8 180.6 171.2 181 164.1 177.2
Hardness After Heat Treatment
Specimen Cutting Speed Feed Rate M1 M1 M1
D13 1 1 184.6 182.2 183.4
D11 1 -1 167.9 152.5 156
D12 -1 1 163.3 170 171.9
D14 -1 -1 152.5 167.9 167.5
D31 1 1 179.5 178.3 179.2
D33 -1 1 175.2 173.1 175.7
D32 1 -1 169.8 155.4 156.2
D34 -1 -1 155.4 170 169
D24 1 -1 165.5 148.5 154.2
D23 -1 1 161.2 160 173
D21 1 1 181.1 180.3 178.2
D22 -1 -1 148.5 165.5 167.3
Hardness After Machining
149
APPENDIX 2 ROUGHNESS RESULTS
Orientation 1
Specimens internal
Number [um] measure 1 (substrate)
measure 2 (central)
measure 3 (extremity)
D21 Ra 14.9 10.3 9
Rq 21.7 15.1 11
Rz 70 62 47.3
PT 188 109 80.2
D22 Ra 11 14.1 10.8
Rq 15.4 18.3 13.8
Rz 62.8 77.7 57.8
PT 133 108 92.8
D23 Ra 13.2 15 18.2
Rq 16.8 20 25
Rz 65.5 79.4 94.7
PT 113 153 187
D24 Ra 15 16.9 11.9
Rq 19.3 20.4 15.6
Rz 73.3 75 63.6
PT 148 117 113
D25 Ra 18.4 18.3 12.7
Rq 25.1 23.9 17.9
Rz 104 88.5 66.5
PT 262 136 152
Orientation 2
D21 Ra 13.5 11.5 11.3
Rq 18.4 14.5 15.2
Rz 73.5 56 61.3
PT 137 134 106
D22 Ra 12.6 12.3 9.57
Rq 18.1 15.9 12
Rz 67.8 62.9 48.8
PT 172 105 82.4
D23 Ra 19.5 12.1 14.9
Rq 25.8 15.7 19.4
Rz 89 62.6 75
PT 164 105 137
D24 Ra 18.3 11.8 12.8
Rq 22.5 15.6 16.9
Rz 90.1 63 69.2
PT 232 98.5 95.9
D25 Ra 11.8 11.1 11.8
Rq 20.1 14.2 14.8
Rz 88.5 52.9 57.4
PT 185 105 91.3
150
Orientation 3
D21 Ra 14.3 17.7 15.7
Rq 20.2 23.6 20.2
Rz 70.2 89.6 85.2
PT 141 151 122
D22 Ra 21.5 18.2 15.7
Rq 27.7 22.8 20.8
Rz 107 91.3 71.1
PT 157 154 163
D23 Ra 12.7 16 15.8
Rq 16.1 20.2 19.1
Rz 66.2 76.6 72.9
PT 112 153 106
D24 Ra 16.8 14.7 12.1
Rq 23.4 18.1 15.5
Rz 83.8 67.4 69.8
PT 210 134 110
D25 Ra 14.8 18.2 15.8
Rq 23.1 22.3 21.4
Rz 106 89.7 76.8
PT 114 131 164
Orientation 4
D21 Ra 14.8 13.8 13.4
Rq 18.7 17.9 16.3
Rz 64.5 70.6 67.1
PT 144 132 119
D22 Ra 9.77 15.4 13.4
Rq 14.2 19.4 17.1
Rz 59.1 75.3 67.9
PT 111 125 110
D23 Ra 18 9.65 13.7
Rq 23.7 12.9 18.5
Rz 82.7 54.6 71.8
PT 174 103 133
D24 Ra 11 10.6 13.8
Rq 18.8 13.4 18.6
Rz 82.4 49.5 69.71
PT 202 121 111
D25 Ra 11.1 15.4 13.3
Rq 17.2 19.5 17.5
Rz 75.6 75.7 67.5
PT 174 163 135
Roughness Results Batch 2 Internal Before Heat Treatment
Orientation 1
Specimens External
151
Number [um] measure 1 (substrate)
measure 2 (central)
measure 3 (extremity)
D21 Ra 8.93 9.08 10.3
Rq 11.9 11.6 14.4
Rz 48.9 44.1 52.4
PT 81.1 86.9 109
D22 Ra 9.69 9.69 8.32
Rq 12.1 13.1 10.4
Rz 44.1 61 36.8
PT 106 112 74.5
D23 Ra 9.69 10 8.43
Rq 13.2 13.8 10.4
Rz 56.3 53 36
PT 86.7 104 90.2
D24 Ra 9.38 8.16 8.51
Rq 11.4 9.88 11.7
Rz 44.7 34.2 48.4
PT 95.7 80 101
D25 Ra 9.35 8.39 8.39
Rq 12.7 9.77 10.2
Rz 48.9 46.3 37
PT 125 85 89.1
Orientation 2
D21 Ra 11 9.16 7.4
Rq 14.8 12.8 9.5
Rz 62.1 48.6 38.3
PT 127 107 71.9
D22 Ra 9.19 9.35 7.67
Rq 11.8 12.6 10.3
Rz 46 42.5 43.9
PT 92.7 77.2 112
D23 Ra 9.19 7.21 7.59
Rq 11.8 9.16 9.69
Rz 43.8 39.2 36.1
PT 75.5 94 96.4
D24 Ra 12.1 10.8 7.59
Rq 16.3 13.7 10
Rz 63.8 52.4 40.7
PT 97.9 107 73.4
D25 Ra 9.77 7.13 7.29
Rq 13 9.96 9.5
Rz 46.1 42.9 40.1
PT 129 90.8 69.1
Orientation 3
D21 Ra 12.1 11.2 8.58
Rq 16.3 14.6 11.2
152
Rz 59.9 56.5 44.2
PT 144 129 102
D22 Ra 9 8.62 7.32
Rq 11.9 11.1 10.4
Rz 41.8 40.3 39
PT 80.5 100 84.1
D23 Ra 9.92 6.79 10.1
Rq 12.9 8.32 13.3
Rz 50.8 33.6 51.7
PT 105 54.1 118
D24 Ra 11.3 6.75 8.47
Rq 14.9 8.39 12.3
Rz 60.2 35.7 46.4
PT 108 68 125
D25 Ra 10.4 8.01 11.6
Rq 13.2 10.2 15
Rz 52.4 47.1 56.3
PT 90.3 70.5 126
Orientation 4
D21 Ra 9.08 9.27 8.54
Rq 12.3 13.1 10.6
Rz 48.3 43.5 40
PT 108 128 67.7
D22 Ra 8.01 11 9.27
Rq 11.1 15 11.7
Rz 44.2 63.8 47.1
PT 97.1 114 84.1
D23 Ra 12.3 7.4 8.28
Rq 15.9 9.88 10.1
Rz 58.1 43.6 40
PT 117 75 77.1
D24 Ra 11.3 7.44 7.71
Rq 15.7 9.42 10.2
Rz 59.4 40.7 37.8
PT 128 61.9 76
D25 Ra 13 10.4 11.4
Rq 16.6 14.1 14.6
Rz 67.1 47.2 55
PT 114 136 89.4
Roughness Results Batch 2 External Before Heat Treatment
Orientation 1
Specimens internal
Number [um] measure 1 (substrate)
measure 2 (central)
measure 3 (extremity)
D11 Ra 16.3 15.6 12.1
Rq 21.4 20.1 18.2
153
Rz 82.7 75.7 71
PT 130 175 136
D12 Ra 16.2 11.6 11.4
Rq 21.2 16.3 14.7
Rz 77.1 68.7 63.9
PT 157 132 89.4
D13 Ra 16 13.3 11.3
Rq 20.8 17.6 15.3
Rz 84.8 73.1 66.1
PT 140 135 113
D14 Ra 13.4 9.61 18.9
Rq 17.4 12.7 25.9
Rz 62 53.1 102
PT 124 85.1 177
D15 Ra 11.3 11 16.2
Rq 15.1 14 22.6
Rz 72.6 60.6 80.1
PT 128 89 174
Orientation 2
D11 Ra 11.3 9.77 9.46
Rq 14 12.7 12.2
Rz 51.7 52.3 56.9
PT 118 92.9 87.3
D12 Ra 13.3 16.5 13
Rq 16.9 22.1 16
Rz 62.7 88.7 62.3
PT 90.3 179 94.2
D13 Ra 20.9 11 15.4
Rq 30.2 14 19.1
Rz 88.4 49.6 70.7
PT 250 107 141
D14 Ra 10.4 19.2 11.1
Rq 13.9 25 15.4
Rz 51.7 91.6 65.2
PT 132 147 107
D15 Ra 18.9 11.9 14.8
Rq 23.4 15.1 19.8
Rz 90.5 59.2 82.6
PT 162 97.4 118
Orientation 3
D11 Ra 15.4 13.4 13.6
Rq 19.4 18.6 16.8
Rz 72.6 66.4 61.3
PT 126 165 124
D12 Ra 13.1 9.61 15
Rq 18 12.2 18.9
154
Rz 65.6 51.3 70.3
PT 124 84.8 119
D13 Ra 14 14.3 12.5
Rq 18.2 18.8 15.7
Rz 72.2 71.9 61.8
PT 141 129 108
D14 Ra 15 13.9 11.8
Rq 18.8 18.3 15.4
Rz 71.6 69.7 60.1
PT 129 141 112
D15 Ra 12.1 14.8 14.2
Rq 15.6 19.2 19.2
Rz 64.5 86.7 84.4
PT 115 139 134
Orientation 4
D11 Ra 15.6 12.8 11.6
Rq 20.9 17.7 14.3
Rz 75.8 70.7 55.5
PT 172 114 98.9
D12 Ra 9.46 13.6 13.9
Rq 12.7 19.2 17.4
Rz 52.6 77.7 73.9
PT 80.9 132 100
D13 Ra 9.31 12.5 11.9
Rq 13.4 16.2 16.3
Rz 48.4 70.2 61
PT 106 130 126
D14 Ra 12.7 16.9 14.5
Rq 18.3 21.7 20.9
Rz 65.6 83.3 83.2
PT 147 128 155
D15 Ra 10.1 15 10.1
Rq 13 18.9 13.6
Rz 54.9 72.2 60.3
PT 91.7 114 114
Roughness Results Batch 1 Internal Before Heat Treatment
Orientation 1
Specimens External
Number [um] measure 1 (substrate)
measure 2 (central)
measure 3 (extremity)
D11 Ra 12.7 7.78 9.92
Rq 18 9.77 12.8
Rz 69.9 37.2 49.4
PT 164 70.3 106
D12 Ra 10.4 11.3 10.8
Rq 13.3 14.7 13.7
155
Rz 54.3 63.3 50.5
PT 89.1 121 80.3
D13 Ra 10.8 10.7 10.8
Rq 14.8 13.4 13.9
Rz 48.7 53.7 53.6
PT 131 76.8 115
D14 Ra 9.16 7.32 8.24
Rq 11.6 9.16 10.7
Rz 49.1 37.1 46.4
PT 83 71.4 82.7
D15 Ra 8.09 6.71 10.8
Rq 10.4 8.54 13.1
Rz 44.1 31.4 49.9
PT 83.8 72 107
Orientation 2
D11 Ra 10.7 14.2 14
Rq 13.1 17.9 18.9
Rz 53.7 67 69.9
PT 84.1 99 130
D12 Ra 10.2 13.6 13.1
Rq 13.4 18 15.9
Rz 51.7 67.4 67.1
PT 98.9 137 91.9
D13 Ra 13.4 10.4 12.5
Rq 18.2 14 16.2
Rz 71.9 60.3 61.7
PT 139 95.1 95.8
D14 Ra 12.8 11 15.6
Rq 16.2 14.3 20.5
Rz 65.5 55.2 69
PT 134 84.5 127
D15 Ra 11.3 8.24 9.31
Rq 14.8 11 12.5
Rz 62.7 43.2 51.7
PT 106 61.7 95.1
Orientation 3
D11 Ra 10.5 10.8 8.85
Rq 13.6 13.9 12.5
Rz 50.5 56.8 55.2
PT 103 91.1 93.5
D12 Ra 9.16 13.4 13.3
Rq 11.8 18.6 18.2
Rz 46.5 67.4 83.6
PT 82.4 136 126
D13 Ra 11.1 13 12.4
Rq 14.3 16.5 15.9
156
Rz 57.8 61.7 65
PT 92 117 109
D14 Ra 10.8 9.61 8.54
Rq 13.7 11.8 11.4
Rz 59.4 42.7 42.6
PT 98 83.9 91.4
D15 Ra 12.7 7.63 12.4
Rq 15.4 9.92 17.6
Rz 55.4 42.7 69.4
PT 129 61.7 116
Orientation 4
D11 Ra 10.4 11.6 7.93
Rq 13.3 15 10.2
Rz 61 58.1 47
PT 106 10 73.1
D12 Ra 10.2 12.1 8.85
Rq 13.4 16.3 12.4
Rz 54.2 64.2 55.1
PT 105 100 91.3
D13 Ra 11.6 9.31 12.2
Rq 14.5 12.8 16
Rz 61.3 46.5 59.2
PT 95.7 93.8 119
D14 Ra 12.1 8.54 9.61
Rq 16.6 10.8 12.1
Rz 60.4 42.3 46.1
PT 137 69.7 125
D15 Ra 10.7 8.85 12.2
Rq 14 11.3 16.6
Rz 56.2 41.8 70.8
PT 82.2 70.2 123
Roughness Results External Batch 1 Before Heat Treatment
Orientation 1
Specimens internal
Number [um] measure 1 (substrate)
measure 2 (central)
measure 3 (extremity)
D31 Ra 8.16 15.5 11.5
Rq 12 19.1 15.1
Rz 44.7 68.9 64
PT 98.3 152 99.3
D32 Ra 12.2 14.9 13.9
Rq 19 19.3 17.7
Rz 52.3 79.3 69.4
PT 172 124 118
D33 Ra 13.7 14.5 11.1
Rq 17.8 20.2 15.3
157
Rz 59.1 79.7 59.4
PT 144 149 113
D34 Ra 10.6 14 15.8
Rq 13.4 19.8 20
Rz 55.9 80.5 71.2
PT 95.4 134 102
D35 Ra 11.2 13.7 13.2
Rq 14.4 19.4 16.2
Rz 62.8 75.7 65.4
PT 106 132 99.6
Orientation 2
D31 Ra 13 14.5 12.1
Rq 18.5 17.9 15.3
Rz 84.3 71 64.7
PT 129 141 94.8
D32 Ra 16.6 17.1 14.7
Rq 23.5 22.2 18.8
Rz 87.4 85.9 75.1
PT 106 150 116
D33 Ra 15 12.7 11.9
Rq 18.8 17.4 15.5
Rz 73.9 71.7 61.5
PT 116 113 103
D34 Ra 11.1 13.6 11
Rq 14.8 18.1 14.3
Rz 58.2 70.1 64.7
PT 124 126 103
D35 Ra 17.5 14.5 15.9
Rq 23.8 18.5 21.1
Rz 94 78.2 93.7
PT 155 126 126
Orientation 3
D31 Ra 10.2 21.3 14.9
Rq 15.2 27.8 19.2
Rz 103 111 77
PT 214 164 99.3
D32 Ra 10.7 12.1 14.8
Rq 14.5 16.2 18.4
Rz 53.3 60.4 73.3
PT 115 119 116
D33 Ra 12.1 17.2 12.7
Rq 15.3 22.6 16
Rz 64.2 91.2 63.5
PT 92.4 140 91.2
D34 Ra 14.7 18 12.5
Rq 18.5 22.7 15.7
158
Rz 74.6 102 69.3
PT 120 147 96.2
D35 Ra 13.6 17.1 12.2
Rq 17.4 24.2 15.8
Rz 68.8 83.7 63
PT 104 172 121
Orientation 4
D31 Ra 15.61 11 13.7
Rq 20.1 14.5 17.3
Rz 76.4 56.8 70.4
PT 123 97 106
D32 Ra 15 10.7 16
Rq 19 14.3 20.1
Rz 74.5 68.5 89.5
PT 128 101 136
D33 Ra 14.5 14.3 15.2
Rq 18.3 18.5 18.1
Rz 73.1 75.3 68.4
PT 134 119 118
D34 Ra 15.1 11.2 14.7
Rq 19.7 15.1 18.9
Rz 77.6 64.2 66.6
PT 139 120 116
D35 Ra 13.8 13.6 12.9
Rq 19.3 17.4 16.5
Rz 76.2 71.2 68.1
PT 128 113 94.4
Roughness Results Internal Batch 3 Before Heat Treatment
Orientation 1
Specimens External
Number [um] measure 1 (substrate)
measure 2 (central)
measure 3 (extremity)
D31 Ra 15.6 9.61 8.16
Rq 20.1 12.6 10.5
Rz 77.4 54.2 37.4
PT 132 86.4 79.6
D32 Ra 15.5 10.5 9.38
Rq 19.2 13.5 12.1
Rz 76.5 53.9 53.2
PT 115 114 85.9
D33 Ra 15 9.84 9
Rq 19 12.3 11.4
Rz 74.4 46 43.4
PT 136 95.6 85.3
D34 Ra 10.4 9.12 7.86
Rq 13 11.6 11.4
159
Rz 52.9 47 39.4
PT 84.4 95.7 93.3
D35 Ra 14.1 10.8 9.3
Rq 18.2 14 12.2
Rz 71.2 51.9 42.4
PT 128 110 105
Orientation 2
D31 Ra 14.1 9.88 10.6
Rq 18.2 13 13.8
Rz 69.5 47.9 53.9
PT 141 96.6 109
D32 Ra 13 8.77 10.4
Rq 16.6 11.2 13
Rz 64.4 39.8 48
PT 121 88.2 87.5
D33 Ra 11.4 8.43 12.3
Rq 15.3 10.2 15.9
Rz 60.5 38 62.9
PT 108 77.9 97.6
D34 Ra 12.4 8.35 13
Rq 15.6 10.7 16.9
Rz 72.3 43 66.8
PT 138 95.3 114
D35 Ra 12.9 10.2 9.84
Rq 15 14.1 13
Rz 57.9 64.8 47.7
PT 105 113 112
Orientation 3
D31 Ra 12.3 9.08 11.3
Rq 16.8 11.8 14.7
Rz 76.3 49.8 61.1
PT 120 87.9 94.8
D32 Ra 12.9 7.97 10.5
Rq 16.7 11 12.8
Rz 69.8 46.9 45.1
PT 108 94.5 94.7
D33 Ra 11.5 10.4 11
Rq 15 13.6 14.1
Rz 65.2 53.7 56.6
PT 101 104 88.6
D34 Ra 12.4 7.97 11.3
Rq 16.4 10.1 14.3
Rz 67 56.7 57.1
PT 102 106 75.5
D35 Ra 12.3 11.8 9.65
Rq 15.8 14.7 12.6
160
Rz 66.4 56.9 48
PT 87.3 103 118
Orientation 4
D31 Ra 10.8 9.73 9.5
Rq 14 12.8 12.6
Rz 56.2 49.8 53.7
PT 88.9 98.5 85.6
D32 Ra 12.7 10.5 11
Rq 16.5 13.2 15.8
Rz 65.1 55.5 63.6
PT 106 82.9 135
D33 Ra 11.3 9.65 8.85
Rq 13.9 12.6 11.3
Rz 56.4 64.4 43.3
PT 104 104 82.7
D34 Ra 12.3 9.73 9.92
Rq 15.6 12.9 12.5
Rz 60.6 67.8 45.1
PT 85.1 144 118
D35 Ra 11.8 10.6 9.73
Rq 14.8 13.4 12.7
Rz 56.9 62.8 54
PT 97.9 77.2 91
Roughness Results Batch 3 External Before Heat Treatment
Orientation1
Specimens internal
Number [um] measure 1 (substrate)
measure 2 (central)
measure 3 (extremity)
D11 Ra 12.5 10 11.6
Rq 15.9 13.1 14.9
Rz 66.9 54.8 68.2
PT 124 87.1 105
D12 Ra 11.3 15.1 11.3
Rq 14.4 19.3 14.5
Rz 61 83.3 57.5
PT 105 125 112
D13 Ra 11.7 10.6 11.4
Rq 15.4 13.7 14.6
Rz 62.1 56.6 56.1
PT 143 98.7 91.4
D14 Ra 9.77 10.2 11.4
Rq 13 14.9 14.5
Rz 51.8 63.9 58.8
PT 102 150 111
Orientation 2
D11 Ra 13.7 10.1 15.7
161
Rq 20.2 13.2 18.8
Rz 77.7 52.5 69.4
PT 153 101 134
D12 Ra 13.3 12.1 13.3
Rq 17.2 15.8 17.3
Rz 73.2 64.7 69.1
PT 125 113 132
D13 Ra 10.6 13.7 13.1
Rq 13.3 17.1 16.5
Rz 55.9 68.6 68.1
PT 80.9 117 117
D14 Ra 8.62 8.32 9.77
Rq 11 10.3 12.4
Rz 45.5 42.9 49.2
PT 77 77.5 86.6
Orientation 3
D11 Ra 14.7 13.4 13.4
Rq 20.5 16.2 18.4
Rz 86.1 61.6 71.3
PT 142 97.2 154
D12 Ra 14.7 12.9 11.8
Rq 19.6 16.3 14.8
Rz 77.1 66.2 59.1
PT 140 113 105
D13 Ra 14.2 13.5 12.8
Rq 19.5 18 16.5
Rz 77 77.4 62.9
PT 148 123 104
D14 Ra 14.7 8.24 11.3
Rq 20.4 10.9 14.6
Rz 85.8 44.7 56.7
PT 153 94.6 132
Orientation 4
D11 Ra 12.4 13 13.4
Rq 15.3 16.3 19.5
Rz 66 62.5 71.9
PT 107 93.3 131
D12 Ra 10.9 11 15.5
Rq 14.1 14 20.5
Rz 58.4 58.6 71.4
PT 136 111 145
D13 Ra 12.8 14.8 13.9
Rq 17.3 18.4 17.6
Rz 71.5 76.8 67.8
PT 123 127 115
D14 Ra 9.31 12.9 14.9
162
Rq 12.6 16.6 19
Rz 54.6 67.4 78.1
PT 77 112 115
Roughness Readings Batch 1 Internal After Heat Treatment
Orientation 1
Specimens External
Number [um] measure 1 (substrate)
measure 2 (central)
measure 3 (extremity)
D11 Ra 12.4 10.7 13.1
Rq 15.6 14.5 16.4
Rz 62.3 60.5 62.3
PT 104 100 114
D12 Ra 9.16 11.1 10.6
Rq 11.8 14.6 13.4
Rz 48.4 55 51.4
PT 76.3 107 99.4
D13 Ra 7.93 11.6 9.69
Rq 9.96 14.9 12.8
Rz 39.1 58.6 50.4
PT 73.5 113 90.9
D14 Ra 8.62 8.58 9.57
Rq 10.5 10.7 12.6
Rz 43.5 39.6 56.1
PT 89 87.2 80.4
Orientation 2
D11 Ra 10.5 9.73 11.1
Rq 13.7 12.4 15.6
Rz 62.5 49.9 61.5
PT 103 103 123
D12 Ra 11.3 11.5 8.96
Rq 14.1 15.6 11.1
Rz 57.1 58 47.6
PT 90.1 126 64.4
D13 Ra 9.57 9.88 11.9
Rq 11.7 13.1 15.6
Rz 45 51.2 70.4
PT 67 98.3 118
D14 Ra 11.1 14.5 14.5
Rq 13.8 18.1 18.5
Rz 50.7 72.4 77.2
PT 107 103 116
Orientation 3
D11 Ra 12.4 9.38 8.81
Rq 16.1 11.1 10.8
Rz 65.7 43.8 45.4
PT 119 70.9 70.1
163
D12 Ra 8.47 7.63 9.61
Rq 10.4 9.61 12.3
Rz 46.2 37.7 47
PT 96.1 74.8 88.8
D13 Ra 8.13 7.82 9.12
Rq 9.96 9.88 11.8
Rz 43 41.1 47.3
PT 85.5 69 92.2
D14 Ra 9.57 10 9.69
Rq 11.9 13.7 12.4
Rz 51.3 49.7 54.1
PT 105 112 77.4
Orientation 4
D11 Ra 8.28 9.19 10.3
Rq 10.5 11.5 13.4
Rz 42.5 45.9 58.9
PT 95 101 107
D12 Ra 7.82 8.28 10.2
Rq 10.1 11 12.6
Rz 46.9 50.3 47.1
PT 83.4 76.4 100
D13 Ra 9.61 11.3 12
Rq 12.1 14.8 15.9
Rz 50.6 63.5 65.2
PT 75.1 104 123
D14 Ra 10.6 7.13 8.35
Rq 14.3 9.12 10.3
Rz 56 38.2 43.8
PT 99.2 59.5 80.1
Roughness Readings External Batch 1 After Heat Treatment
Orientation1
Specimens internal
Number [um] measure 1 (substrate)
measure 2 (central)
measure 3 (extremity)
D21 Ra 12.1 11.3 10.3
Rq 11.4 14.6 12.7
Rz 43.3 58.9 52.8
PT 108 103 96
D22 Ra 12.6 10 13.1
Rq 16.1 12.4 17.3
Rz 68.4 46.8 65.4
PT 124 87.1 124
D23 Ra 13.1 12.1 9.31
Rq 17.8 16.3 11.8
Rz 78.5 71.9 48
PT 133 119 87.2
164
D24 Ra 14.1 10.6 12.9
Rq 17.7 13.3 17.7
Rz 68.9 54.7 68.5
PT 118 107 125
Orientation 2
D21 Ra 12.3 13.2 13
Rq 16.6 17.3 17.5
Rz 69.3 70.5 73.3
PT 118 142 145
D22 Ra 13.9 11.2 9.8
Rq 20.3 14.9 12.4
Rz 73.8 67.1 52.5
PT 149 97.5 91.1
D23 Ra 13 11.1 13.2
Rq 17.6 14.4 16.8
Rz 75 58.7 62.4
PT 144 98.3 129
D24 Ra 12.6 10.1 12.7
Rq 16.8 13 15.8
Rz 65.9 51.5 68.8
PT 110 104 118
Orientation 3
D21 Ra 14.2 9.57 13.1
Rq 18.3 11.8 17.2
Rz 69.9 53.3 67.1
PT 116 79.6 123
D22 Ra 11.2 14.9 13.2
Rq 15 17.6 16.4
Rz 54.5 62.3 62.8
PT 101 114 108
D23 Ra 13 13.6 14.7
Rq 17.8 18.5 19.4
Rz 68.7 72.3 68.4
PT 122 105 156
D24 Ra 13.9 14.8 13.8
Rq 17.7 19.9 17.5
Rz 72.7 88.3 72
PT 111 138 99
Orientation 4
D21 Ra 11.4 14.4 12.2
Rq 14.9 18.7 15.4
Rz 60.5 77 63.2
PT 134 116 99.1
D22 Ra 12 12.3 11.6
Rq 16.8 16.3 14.6
Rz 68.5 62 60.2
165
PT 136 106 88.7
D23 Ra 16.2 13.4 12.1
Rq 20.5 16.4 15.8
Rz 74.8 74.1 67.7
PT 148 111 113
D24 Ra 12.5 11.7 9.96
Rq 16.4 16.5 14.7
Rz 69.5 64.7 55.7
PT 146 113 102
Roughness Readings Internal Batch 2 After Heat Treatment
Orientation1
Specimens External
Number [um] measure 1 (substrate)
measure 2 (central)
measure 3 (extremity)
D21 Ra 9.5 9.77 10.2
Rq 12.4 12.5 12.9
Rz 49.9 48.8 51.4
PT 107 95.2 105.2
D22 Ra 9 6.45 9.04
Rq 11.4 8.47 11.1
Rz 45.4 34.3 42
PT 105 50.9 74.8
D23 Ra 10.7 7.44 8.77
Rq 13.3 9.77 12.2
Rz 49.4 41.7 45.7
PT 94.4 83.5 107
D24 Ra 10.9 8.7 7.63
Rq 13.4 10.8 9.88
Rz 52.8 43.3 38.3
PT 90.3 77.3 87.2
Orientation 2
D21 Ra 9.77 8.16 7.74
Rq 12.7 11.1 10.5
Rz 54.9 40.8 44.4
PT 84.6 84.8 76.4
D22 Ra 9.35 8.89 8.2
Rq 12 12.1 10.1
Rz 49.6 44.5 39.1
PT 85.4 74.8 82.2
D23 Ra 10.6 8.85 6.98
Rq 13.3 11.8 9.08
Rz 52.4 47 37.8
PT 97.6 87.8 76.6
D24 Ra 10.2 7.97 6.71
Rq 13.1 10 8.51
Rz 53.6 38.9 33.3
166
PT 86.3 59.8 59.3
Orientation 3
D21 Ra 10.7 10.8 10.3
Rq 15.8 12.6 13.3
Rz 59.8 43.8 49.2
PT 130 85.2 101
D22 Ra 11 9.27 9.31
Rq 16.9 10.8 11.1
Rz 60.9 36.2 41.3
PT 142 73 80.6
D23 Ra 11.1 6.52 8.05
Rq 13.9 8.24 9.96
Rz 55.9 33.1 41.2
PT 83.5 57.2 69.8
D24 Ra 11.8 7.63 8.16
Rq 15.1 9.92 11.3
Rz 61.9 40.3 41.5
PT 115 73 88.3
Orientation 4
D21 Ra 9.27 7.25 6.48
Rq 11.8 9.88 8.39
Rz 50.5 37.9 34.3
PT 85.1 75.7 73
D22 Ra 8.81 6.56 9.04
Rq 11.4 8.35 10.9
Rz 48 33 39.6
PT 68.8 69.4 71.3
D23 Ra 9.77 7.13 7.9
Rq 14.5 9.04 10
Rz 54.8 37 39.8
PT 114 95.7 69
D24 Ra 7.44 7.97 6.14
Rq 9.32 10.56 7.75
Rz 36 51.45 33.2
PT 81.5 114 61.8
Roughness Readings Batch 2 External After Heat Treatment
Orientation1
Specimens internal
Number [um] measure 1 (substrate)
measure 2 (central)
measure 3 (extremity)
D31 Ra 14.4 13.6 11.8
Rq 18.5 17.9 14.9
Rz 70.4 69 61
PT 136 123 97.2
D32 Ra 11.3 13.7 11.1
Rq 14.7 17.7 14.2
167
Rz 65.7 67.4 49.1
PT 118 138 98.4
D33 Ra 14.9 12.8 15.2
Rq 19.1 16.6 20.4
Rz 70.8 64 75.4
PT 167 125 136
D34 Ra 12.5 12.6 13.4
Rq 16.5 16.6 16.4
Rz 63.7 63.5 69.7
PT 121 91.6 103
Orientation 2
D31 Ra 15.5 13.4 13.4
Rq 20.5 17.5 17.2
Rz 79.3 68.4 67.9
PT 164 127 118
D32 Ra 12.9 14.1 12.2
Rq 16.3 19.5 15.9
Rz 67.8 75.4 65.9
PT 114 154 109
D33 Ra 13.4 11.1 13.4
Rq 17.2 13.8 16.7
Rz 73.3 55.1 65.3
PT 117 101 101
D34 Ra 9.88 13.5 12.7
Rq 12.6 17.9 16.8
Rz 57 77.9 68.2
PT 79.7 105 124
Orientation 3
D31 Ra 11 12 14.4
Rq 15.8 14.6 18.9
Rz 54.4 57.8 76.4
PT 91.1 104 118
D32 Ra 14 9.42 12.4
Rq 19.6 12.3 17.3
Rz 68.3 53 65.1
PT 153 85.7 120
D33 Ra 12.8 16 10.9
Rq 16.4 20.1 15.1
Rz 64.2 79.2 66.6
PT 126 143 118
D34 Ra 13.7 12.5 12
Rq 18.5 18.3 15
Rz 84.2 83 61.3
PT 132 156 107
Orientation 4
D31 Ra 14.4 12.7 14
168
Rq 19.2 15.9 18.9
Rz 75.7 62.7 71.9
PT 149 123 148
D32 Ra 15.9 10.6 12.5
Rq 20.2 14.3 16.5
Rz 85.8 55.7 66.8
PT 119 108 103
D33 Ra 13.9 13.9 15.2
Rq 17.6 18.7 20
Rz 73.4 77.8 87.2
PT 130 144 135
D34 Ra 13.4 10.9 13.6
Rq 16.8 14.3 16.9
Rz 60.8 61.5 72.7
PT 150 87.9 123
Roughness Readings Batch 3 Internal After Heat Treatment
Orientation1
Specimens internal
Number [um] measure 1 (substrate)
measure 2 (central)
measure 3 (extremity)
D31 Ra 11 9.74 10.3
Rq 13.6 12.8 13.4
Rz 58.4 62.6 58.8
PT 105 104.4 108
D32 Ra 11.4 11.9 9.73
Rq 15.1 15.6 12.4
Rz 60.5 56.4 51.9
PT 129 113 109
D33 Ra 11.2 9.65 9.96
Rq 13.4 12.4 13
Rz 50.9 52.6 56.6
PT 110 85.8 92.8
D34 Ra 10 10.2 7.29
Rq 12.1 12.9 9.57
Rz 46.4 55.8 40.5
PT 76 106 79.1
Orientation 2
D31 Ra 11.1 9 8.85
Rq 13.5 11.3 11.4
Rz 52.4 40.6 49.1
PT 122 86.3 85.3
D32 Ra 8.35 8.43 8.2
Rq 11 10.2 10.2
Rz 42.2 40.4 42.6
PT 78.7 71.4 83.5
D33 Ra 8.2 8.54 8.66
169
Rq 10.8 10.3 10.6
Rz 48.1 40 37.2
PT 71.2 59.6 68.3
D34 Ra 9.08 8.7 9.1
Rq 11.8 12.4 9.16
Rz 44.4 46.8 37.7
PT 83.5 80.6 86.8
Orientation 3
D31 Ra 13 8.85 8.54
Rq 17.3 11.7 10.9
Rz 85.3 48.8 38.8
PT 113 71.6 76.8
D32 Ra 9.92 8.81 8.16
Rq 12.3 11.5 11.5
Rz 42 40.8 50.7
PT 100 116 100
D33 Ra 9.73 8.66 8.93
Rq 12.2 10.9 10.8
Rz 51.4 42.1 40.1
PT 67.6 84 62.6
D34 Ra 10.4 9.8 11.3
Rq 12.7 13.9 14.7
Rz 44.4 58.8 52.8
PT 72.7 110 102
Orientation 4
D31 Ra 9.46 7.97 9.35
Rq 13.2 9.96 12
Rz 53.6 40.6 49.4
PT 91.2 78.8 83
D32 Ra 13.2 8.85 11.2
Rq 16.8 11.8 15.8
Rz 63.4 50.6 53.2
PT 106 87.3 135
D33 Ra 9.54 11.8 9.19
Rq 11.8 13.8 11.6
Rz 43.6 51.2 51.1
PT 93.7 85 110
D34 Ra 9 8.16 9.65
Rq 11.6 9.88 12.4
Rz 43.9 41.7 50.2
PT 105 59.7 85.1
Roughness Readings Batch 3 External After Heat Treatment