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UNIVERSITI TEKNIKAL MALAYSIA MELAKA
THE STUDY OF SIZE EFFECT ON SURFACE FINISH WHEN
HARD TURNING AISI D2 TOOL STEEL
This report submitted in accordance with requirement of the Universiti Teknikal
Malaysia Melaka (UTeM) for the Bachelor Degree of Manufacturing Engineering
(Manufacturing Process) with Honours.
By
MOHD AIZAT BIN A. HAMID
FACULTY OF MANUFACTURING ENGINEERING
UNIVERSITI TEKNIKAL MALAYSIA MELAKA
BORANG PENGESAHAN STATUS LAPORAN PSM
TAJUK: “The Study of Size Effect on Surface Finish when Hard Turning AISI D2 Tool Steel”
SESI PENGAJIAN: 2008/2009 Semester 2
Saya MOHD AIZAT BIN A. HAMIDmengaku membenarkan laporan PSM ini disimpan di Perpustakaan Universiti Teknikal Malaysia Melaka (UTeM) dengan syarat-syarat kegunaan seperti berikut:
1. Laporan PSM / tesis adalah hak milik Universiti Teknikal Malaysia Melaka dan penulis.2. Perpustakaan Universiti Teknikal Malaysia Melaka dibenarkan membuat salinan untuk tujuan pengajian sahaja dengan izin penulis.3. Perpustakaan dibenarkan membuat salinan laporan PSM / tesis ini sebagai bahan pertukaran antara institusi pengajian tinggi.4. *Sila tandakan (√)
SULIT
TERHAD
TIDAK TERHAD
(Mengandungi maklumat yang berdarjah keselamatan atau kepentingan Malaysia yang termaktub di dalam AKTA RAHSIA RASMI 1972)
(Mengandungi maklumat TERHAD yang telah ditentukan oleh organisasi/badan di mana penyelidikan dijalankan)
6, JALAN IKHLAS 7,BANDAR TUN RAZAK,56000 CHERAS, W. PERSEKUTUAN (KL)
Tarikh: _______________________
Cop Rasmi:
Tarikh: _______________________
* Jika laporan PSM ini SULIT atau TERHAD, sila lampirkan surat daripada pihak organisasi berkenaan dengan menyatakan sekali sebab dan tempoh tesis ini perlu dikelaskan sebagai SULIT atau TERHAD.
APPROVAL
This report is submitted to the Faculty of Manufacturing Engineering of UTeM as a
partial fulfillment of the requirements for the degree of Bachelor of Manufacturing
Engineering (Manufacturing Process) with Honours. The member of the supervisory
committee is as follow:
(Signature of Supervisor)
……………………………………………..
(Official Stamp of Supervisor)
ABSTRACT
The introduction of hard turning has provided an alternative to the conventional
processing technology used to manufacture parts made from hardened steels. Shorter
product development time along with being more environmentally friendly are among
the benefits offered by hard turning, which potentially results in lower manufacturing
cost per part. However, common tool materials for hard turning applications are
expensive. Due to the continuous developments in cutting tool materials and coating
technology, inexpensive coated carbide cutting tools are being investigated to determine
the potential of using them for use in extreme conditions as in hard turning. TiN coated
carbide tool was selected to finish machine hardened steel. Performing hard turning at
various workpiece size revealed that the surface finish values of 0.68 µm that meet the
strict range of finish machining of workpiece diameter of 70 mm and 0.77 µm of finish
machining of workpiece diameter of 100 mm were obtained when finish machining
hardened steel of 45 HRC hardness. The results show that smooth surface finish was
influenced by workpiece diameter.
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ABSTRAK
Pengenalan kepada larikan keras telah menyediakan satu alternatif untuk
teknologi pemprosesan yang konvensional untuk mengeluarkan bahagian-bahagian yang
diperbuat daripada keluli keras. Masa pembangunan produk yang lebih pendek bersama
dengan menjadi lebih mesra alam adalah antara faedah ditawarkan oleh larikan keras,
yang berpotensi mengakibatkan kos perkilangan lebih rendah setiap bahagian.
Walaubagaimanapun, bahan-bahan alat biasa untuk aplikasi-aplikasi larikan keras adalah
mahal, bersandarkan kepada pembangunan yang berterusan dalam bahan-bahan
perkakas pemotongan dan teknologi saduran, mata alat memotong karbida yang bersalut
adalah diselidiki untuk menentukan potensi menggunakannya untuk penggunaan dalam
proses pemesinan seperti yang terdapat dalam peralihan keras. TiN karbida bersalut
telah dipilih untuk menghabiskan proses pemesinan keluli keras. Hasil larikan keras
pada pelbagai saiz benda kerja menunjukkan nilai hasil permukaan 0.68 µm apabila
menjalankan proses pemesinan diameter benda kerja 70 mm dan 0.77 µm apabila
menjalankan proses pemesinan diameter benda kerja 100 mm telah diperolehi apabila
pemesinan akhir keluli keras yang mempunyai kekerasan 45 HRC. Keputusan
menunjukkan permukaan benda kerja yang baik dipengaruhi oleh diameter benda kerja.
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ACKNOWLEDGEMENT
The author wishes to express his most sincere appreciate to his supervisor, Dr.
Ahmad Kamely Bin Mohamad of the department of Manufacturing Process for
providing tremendous technical guidance, advices, continuous encouragement,
constructive criticisms, suggestions throughout this project and administrative support
during this project. Sincere thanks is extended wish to the general, his examiner, Dr.
Bagas Wardono and fellow friends for their corporation and help during the period of
this project. The author always appreciates to the Faculty of Manufacturing Engineering,
Universiti Teknikal Malaysia Melaka (UTeM) for providing the facilities for this
project.
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DEDICATION
Specially dedicated for my beloved father, A. Hamid Bin A. Rahman and my mother, Siti
Rohani Binti Che Omar who are very concerns, understanding patient and supporting.
Thank you for everything to my supervisor, Dr. Ahmad Kamely Bin Mohamad, my
sisters, my brothers and all my friends. The work and success will never be achieved
without all of you
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TABLE OF CONTENT
Abstract i
Abstrak ii
Acknowledgement iii
Dedication iv
Table of Content v
List of Tables viii
List of Figures ix
List of Abbreviations xi
1. INTRODUCTION 1
1.1 Background 1
1.2 Problems Statement 2
1.3 Objectives 3
1.4 Scope of Work 3
1.5 Significance of the Study 3
v
2. LITERATURE REVIEW 4
2.1 Introduction 4
2.2 Hard Turning 5
2.2.1 Parameters in Hard Turning 6
2.3 Hard Turning Using TiAIN Coated Carbide Tool 7
2.4 Hard Turning of Stainless Steel Using Wiper Coated Carbide Tool 8
2.5 Performance of Coated Carbide Tools in Hard Turning 10
2.6 Wear 11
2.7 Coating 13
2.8 Surface Finish 14
2.9 The Relationship Between the Work Piece Extension Length/Diameter 19
Ratio and Surface Roughness in Turning Applications
2.10 Dynamic Instability of the Hard Turning Process 21
3. RESEARCH METHODOLOGY 23
3.1 Introduction 23
3.2 Cutting Condition 24
3.3 Tool Wear Standard 25
3.4 Workpiece Material 27
3.5 Surface Roughness Measurement 30
PSM 1 Gantt Chart 32
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4. RESLUTS AND DISCUSSION 33
4.1 Surface Finish 34
4.2 Influence of the Tool Nose Radius 38
4.3 Influence of the Dry Cut Finishing 39
4.4 Influence of the Workpiece Diameter 40
4.5 Motion Capability and Machine Accuracy 41
5. CONCLUSION AND RECOMMENDATION 42
5.1 Conclusion 42
5.2 Recommendation 43
GANTT CHART 44
REFERENCES 55
LIST OF APPENDICES 53
vii
LIST OF TABLES
3.1 Tools technical details and cutting conditions (Tool’s catalogue). 25
3.2 Properties of tungsten carbide and coating materials (Tool’s catalogue). 25
3.3 Recommendations used in industrial practice for limit of flank wear VBB
for several cutting materials (Astakhov and Davim, 2008). 27
3.4 AISI D2 properties (Tool’s catalogue). 28
3.5 Cutting data parameters for turning (Tool’s catalogue). 29
4.1 Results of surface roughness of cutting parameter. 35
4.2 Results of surface roughness of cutting parameter. 35
LIST OF FIGURES
viii
2.1 Typical wear pattern and pertinent terminology. 12
2.2 Illustration of surface roughness. 15
2.3 Surface roughness vs. tool wear. 16
2.4 Surface roughness (Ra and Rmax) and flank wear vs. 17
length of cutting.
2.5 Surface roughness vs. cutting length (lc) for different 17
cutting speeds.
2.6 Surface roughness measurements vs. cutting speed. 18
3.1 f = feed, r = corner radius and Ra = surface finish. 24
3.2 Types of tool wear according to standard ISO 3685:1993. 26
3.3 Progressive die made of AISI D2. Long run tooling for 29
blanking of parts in thin sheets.
3.4 Center drilling the work pieces. 30
3.5 Profilometer of Surface roughness Tester Mitutoyo SJ-301. 31
4.1 The diagram of average surface roughness value (Ra) obtained by 34
processing AISI D2 tool steel with coated carbide cutting tool at
200 mm/min cutting speed and 0.16 mm/rev feed rate.
4.2 The average surface roughness (Ra) obtained by processing the 36
AISI D2 tool steel with different cutters at constant cutting speeds
and at chosen 0.16 mm/rev feed rates.
4.3 The average surface roughness (Ra) obtained by processing 36
the AISI D2 tool steel with different spindle speed (rpm)
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CNC - Computer Numerical Control
CBN - Cubic Boron Nitride
VB - Average Wear Land Width
VBmax - Maximum Wear Land Width
PVD - Physical Vapor Deposition
ISO - International Standard Organization
Fe3C - Ferum Carbide
TiC - Titanium Carbide
TiN - Titanium Nitride
Al2O3 - Aluminum Oxide
TiO2 - Titanium Oxide
AA - Arithmetic Average
Vb - Flank Wear
Ra - Surface Roughness
VA - Front face wear
µm - micron meter
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CHAPTER 1
INTRODUCTION
1.1 Background
In the manufacturing industries, mold and die making usually refers to the parts
produced that are asymmetrical in shape. Sheet metal components are of various shapes,
and injection molded plastic parts range from household appliances to consumer
electronics. Hard turning is applied to make a die and mold to produce variety of plastic
parts.
Hard turning is a single point machining process, is carried out on a lathe and
carried out on hard materials which have Rockwell C hardness greater than 45. The
process is intended to replace or limit traditional grinding operations that are expensive,
environmentally unfriendly, and inflexible. Hard turning, when applied for purely stock
removal purposes, competes favorably with rough grinding. However, when it is applied
for finishing where form and dimension are critical, grinding is superior.
First introduced around 1926, cemented carbides are the most popular and most
common high production tool materials available today (Metals Handbook, 1980). The
productivity enhancement of manufacturing processes imposes the acceleration of the
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design and evolution of improved cutting tools with respect to the achievement of a
superior tribological attainment and wear resistance (Bouzakis, 2000).
One important aspect that is being vigorously researched and developed is the
hard coating for cutting tools. These hard coatings are thin films that range from one
layer to hundreds of layers and have thickness that range from few nanometers to few
millimeters. These hard coatings have been proven to increase the tool life by as much
as 10 folds through slowing down the wear phenomenon of the cutting tools. This
increase in tool life allows for less frequent tool changes, therefore increasing the batch
sizes that could be manufactured and in turn, not only reducing manufacturing cost, but
also reducing the setup time as well as the setup cost (Nouilati, 2002).
Surface finish influences not only to the dimensional accuracy of machined parts
but also their properties and their performance in service. The term surface finish
describes the geometry features of a surface, and surface integrity pertains to material
properties, such as fatigue life and corrosion resistance, which are strongly influenced by
the nature of the surface produced. The quality of machined surface is characterized by
the accuracy of its manufacture with respect to the dimensions specified by the designer.
Every machining operation leaves characteristic evidence on the machined surface. This
evidence in the form of finely spaced micro irregularities left by the cutting tool. Each
type of cutting tool leaves its own individual pattern which therefore can be identified.
This pattern is known as surface finish or surface roughness.
In addition to increasing the tool life, hard coating deposited on cutting tools
allows for improved and more consistent surface roughness of the machined work piece.
The surface roughness of the machined workpiece changes as the diameter of the
workpiece changes due to cutting speed in revolutions per minute (rpm).
1.2 Problems Statement
In machining of parts, surface quality is one of the most important that specified
customer requirements. Major indication of surface quality of machine parts is surface
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roughness. Roughness is often closely related to the friction and wear properties of a
surface. There are various machining parameters that have an effect of the surface
roughness, but size effect has not been adequately quantified.
1.3 Objectives
The objective of this study is to investigate the influences of the workpiece size on
surface finish when hard turning AISI D2 tool steel of 45 HRC with carbide cutting tool.
Besides that, the influence of size effect on surface morphology is also been deserve.
1.4 Scope of Work
This study will aim an experimental investigation with coated carbide tools in turning
hardened AISI D2 steel of 45 HRC, aiming at determining the most suitable parameters
and material characteristics. To achieve this goal, turning tests were conducted with a
CNC lathe using commercially available carbide cutting inserts. The surface finish of the
workpiece will be measure by using surface roughness profilometer.
1.5 Significance of the Study
Many factors will affect the performance of a component. Some of the more commonly
discussed factor is surface finish. The surface finish has a significant effect on fatigue
strength of a component such as bearing. Fortunately, the study of size effect on surface
finish is still not adequate and need to be research for further understanding.
3
CHAPTER 2
LITERATURE REVIEW
2.1 Introduction
The introduction of hard turning has provided an alternative to the usual processing
technology used to manufacture parts made from hardened steels. Shorter product
development time along with being more environmentally friendly are among the
benefits offered by hard turning, which potentially results in lower manufacturing cost
per part. However, common tool materials for hard turning applications are expensive.
Due to the continuous developments in cutting tool materials and coating technology,
inexpensive coated carbide cutting tools are being investigated to determine the potential
of using them for use in extreme conditions as in hard turning. Coated carbide tool was
selected to finish machine hardened steel. Performing hard turning dry at various cutting
conditions, that is, cutting speed and feed rate, revealed that suitable tool life and surface
finish values that meet the strict range of finish machining were obtained when finish
machining hardened steel of 58 HRC hardness (Noordin, 2007).
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2.2 Hard Turning
One of the reasons hard turning is coming to the forefront of manufacturing is because
people are trying to reduce the lead times it takes to get a part from raw material to the
customer. It’s a lean manufacturing initiative. The thing that can do with hard turning,
that is difficult to do with grinding, is hard turning can start with a solid blank material
and produce a finished component complete on one machine. In hard turning, it can start
with a pre hardened material and machine it and can skip several steps and actually cut
days out of the process.
Choosing hard turning is really application driven, because it’s dependent on the part.
Grinding is better suited if it have really thin walled parts or parts that are delicate from
a crushing perspective. If it have a surface finish that requires a different type of texture,
for example, when turning, it will creating a thread and when grinding it will get a
checking. If look at it under a microscope, it would be a pitted surface finish. When
honing, it will get cross checking surface finish. If this part has oil lubrication near it or
running across the surface, the turned part would actually screw the oil through from one
side to another. With grinding, the oil would be held there because it’s pitted or cross
checked.
Places where hard turning is very well suited is when it have complex figures, such as
contour radii, angles and diameters all on one part. Hard turning can do that in one
setting. Besides the actual process and efficiency of hard turning, this type of machining
is gaining popularity because the overall function is less expensive today. It’s becoming
more popular because hard turning is usually less expensive to do because it is faster, the
machines cost less and operator learning curve is less. The operator has to learn the one
machine and the one machine does it all. Hard turning also offers smaller benefits that
can be time saving and environmentally friendly. When grinding, it will get a lot of fine
particles and have to clean it out and have a special filtration unit on which to have to
5
clean regularly. With turning, it will producing steel chips, which are much easier to
dispose of or recycle (Ferguson, 2004).
2.2.1 Parameters in Hard Turning
Four typical characteristics of hard turning as opposed to grinding have been stated
below:
a. The significantly higher cutting force.
b. The omission of coolant.
c. The single point form generation.
d. The minimum value of the depth of cut.
The cutting force occurring in hard turning is higher than conventional turning or
grinding. The passive force occurring in hard turning is the component perpendicular to
the cutting speed and is a multiple of the main cutting force, while in traditional turning
it is only a fraction of this value. The extraordinarily high passive force, which
contributes to the material removal, significantly loads the elements of the machining
system. The disadvantageous effect of the high passive force must be compensated for
by an increase in machine tool rigidity.
Hard turning can be done in dry conditions at relatively high speed. The relative high
friction coefficient and the passive force cause a significant friction force which
transforms into heat. The other source of the generated heat is the high cutting speed.
The high temperature generated during material removal causes thermal expansion of
the work piece.
The surface generating element of hard turning is the single point tool tip, which shapes
the surface of the work piece and is accompanied by significant force and heat effects.
Under such conditions is the single point tool tip reacts sensitively to any irregularities.
The last parameter discussed for hard turning is the depth of cut. In hard turning this
cannot be reduced significantly, although this is possible in grinding. Because of the
necessity of a minimum depth of cut, hard turning is followed by higher forces than in
grinding, even in the finest smoothing operations. (Kundrak, 2006).
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2.3 Hard Turning Using TiAIN Coated Carbide Tool
Components made from hardened steels are increasing in numbers driven by the need
for high performance. Hardened steel’s properties of high wear resistance and
compressive strength meet the demands in automotive, tool and die industries. Machine
shop being an integral portion of the manufacturing system needs to modify the
machining process flow in order to be able to machine parts made from these hard to cut
materials more effectively. The usual technique to manufacture hardened parts involves
three sequential steps, that is, rough machining of unhardened steel, heat treating the
steel to the required hardness and finish machining to the required dimensional accuracy.
Normally, heat treatment is being done externally thereby leading to longer lead times.
The introduction of hard turning using tools with high hot hardness (Polycrystalline
Cubic Boron Nitride (PCBN) and ceramic) has simplified the process flow by allowing
the steel blank to be machined to its final dimension in the hardened state (Poulachon et
al., 2003). Hard turning refers to the turning of hardened steels with a hardness of
beyond 45 HRC. The hardness can even reach 68 HRC. This technique became a
profitable alternative for finish machining due to advantage in economical and
ecological aspects. High material removal rate and relatively low tool cost compared to
the incumbent grinding as the finishing operation are some of the economical benefits.
Additionally, stricter health and environment regulations and also post production cost
consideration led to the minimized use of coolant whenever feasible and hard turning
has been successfully performed in dry condition (Mamalis et al., 2002).
Despite its significant advantages, the lack of data concerning surface quality and tool
wear for the many combinations of work piece and cutting tool impedes the acceptance
of hard turning by the manufacturing industry (Pavel et al., 2005). Moreover, the
common tools used in hard turning, PCBN and ceramic, are relatively high in price.
Some applications in the mould and die industry have been identified to require parts
made of hardened steels within the moderate range of hard turning (45–48 HRC). Using
advanced and consequently expensive cutting tools for these moderate hardness ranges
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may hinder the economical benefit of hard turning. Previous hard turning of stainless
steel (43–45 HRC) has been successfully performed using coated carbide tool (Noordin
et al., 2007). It is likely that coated carbide tool has the potential to turn steels of even
higher hardness within the moderate range of hard turning. This is because of the
continuous development of carbide tool taking place in the form of fine grained
substrate, better binder that optimizes strength and toughness and improved coating
using Physical Vapor Deposition (PVD) technique. Therefore, the potential of using
inexpensive coated carbide cutting tools needs to be investigated.
In order to encourage machine shops to fully adopt hard turning, assessments should be
made to clarify the aspects of the tool life and machined surface’s quality. The
machining cost per part is a function of tool life and, thus, machine shops demand long
tool life. Additionally, finish machining should produce fine surface finish as requested
by the users of the machined parts to meet the specific requirements of certain
application (Gillibrand et al., 1996). Therefore, in order to generate information on the
performance of coated carbide tool and the resulting machined surface, hard turning was
conducted using various cutting parameters within finish machining parameters.
2.4 Hard Turning of Stainless Steel Using Wiper Coated Carbide Tool
Hard turning has been explored as an alternative to grinding for finish machining of
machine parts made of hardened steels. The introduction of tools with high hot hardness
(Polycrystalline Cubic Boron Nitride (PCBN) and ceramic) has contributed in enabling a
hardened steel blank to be finish machined by single point turning process. Hard turning
simplifies the current technique to manufacture hardened parts which involve three
sequential steps, for example, rough machining of unhardened steel, heat treating to the
required hardness and finish machining to the required dimensional accuracy. Potential
advantages in economical and ecological aspects have made hard turning a profitable
alternative to the incumbent grinding as the finishing operation. High material removal
rate and relatively low tool cost are some of the economical benefits. Nevertheless, the
drive to minimize the use of coolant whenever feasible has advantaged hard turning
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which has been successfully performed in dry condition (Mamalis et al., 2002 and
Noordin et al., 2007).
Along with developing researches and studies, types of materials being cut by hard
turning method are growing in numbers and applications. Stainless steel is among the
materials being investigated to employ hard turning method due to its wide application
in automotive, tool and die industries. High wear resistance and compressive strength
are some properties required for some high performance parts. Martensitic stainless steel
seems the appropriate type of stainless steel since it is hardenable by quenching and
tempering and therefore can achieve high strength and hardness levels (Sourmail and
Bhadeshia, 2005).
However, the advanced tools commonly used in hard turning, PCBN and ceramic, are
relatively high in price. The need for lower cost tool materials to perform hard turning is
still on demand. Coated carbide tool is the proposed alternative for some applications
within moderate range of hard turning. Recent development has provided commercially
available coated carbide tools very fine substrate grain size, modified binder that
optimizes strength and toughness, and improved coating using Physical Vapor
Deposition (PVD) technique which may ensure reasonable tool life at minimal cost per
cutting edge (Jindal et al., 1999).
Finish machining is intended to achieve high level of surface finish and is characterized
with low feed and depth of cut (Shaw, 2005). In order to improve the productivity, tools
with wiper geometry have been provided by tool manufacturers. This tool geometry has
wiper radii adjacent to the nose radius and has little or no clearance angle to improve
finish by burnishing action by the flank face of the insert (Shaw, 2005). This
modification can double the current feed and still achieve surface finishes comparable to
conventional inserts. Alternatively, if surface finish is the most important consideration,
then the same feed can be maintained to achieve better surface roughness values
(Castner, 2000).
2.5 Performance of Coated Carbide Tools in Hard Turning
9
The use of coating materials to enhance the performance of cutting tools is not a new
concept. The first coated carbide indexable inserts for turning were introduced in 1969
and had an immediate impact on the metal cutting industry (Soderberg, 2001). The boost
in wear resistance gave room for a significant increase in cutting speed and thereby
improved productivity at the machine shop floor. And today, 70% of the carbide tools
used in the industry are coated (Abdullah, 1996).
In development of modern materials, the functionality is often improved by combining
several materials of different properties into composites. Many classes of composites
exist, most of which are addressing improved mechanical properties such as stiffness,
strength, toughness and resistance to fatigue. Coating composites are designed to
specifically improve tribological and chemical functions. It is thus natural to select the
bulk of a component to meet the demands for stiffness, strength, toughness, formability,
cost, and then modify or add another material as a thin surface layer. This surface layer
or coating is the carrier of virtually all other functional properties. Application of
coatings on tools and machine elements is, therefore, a very efficient way of improving
their friction and wear resistance properties (Hogmark, 2000).
The combined substrate coating properties ultimately determine the important properties
such as wear, abrasion resistance and adhesion strength of a coating. A hard wear
resistant coating cannot perform well unless complimented by a hard and tough
substrate. Thus, a hard coating deposited on a soft substrate leads to poor properties
(Deevi, 2003).
Due to their significantly higher hardness, carbide cutting tools are more widely used in
the manufacturing industry today than high speed steels. Coated and uncoated carbides
are widely used in the manufacturing industry and provide the best alternative for most
turning operations (Haron, 2001). Due to their heat resistance, coated carbides can be
used in very hot applications and all types of PVD and CVD processes can be used to
deposit coatings (Armarego, 2002).
Physically and chemically vapor deposited coatings offer today a powerful alternative to
improve further the cutting performance of the cutting materials (Bozakis, 2000).
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