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Thermally Sprayed CoatingsThermally Sprayed Coatingsand their Characterizationand their Characterization

TechniquesTechniques

EMPA-ThunEMPA-Thun

St. Siegmann,St. Siegmann,O. Brandt, M. O. Brandt, M. AeberhardAeberhard

CEAC Summer Workshop 1999:CEAC Summer Workshop 1999:FunctionalizedFunctionalized Surfaces: Application and Analytical Tools Surfaces: Application and Analytical Tools

July 5-6, 1999July 5-6, 1999----------------------------------------------------------------------------------------

----------------------------------------------------------------------------------------

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Thermally Sprayed Coatings andThermally Sprayed Coatings andtheir Characterization Techniquestheir Characterization Techniques

1. Thermal Spraying �Coating Morphology 2. Characterization Techniques:

2.1 Destructive Test Methods:- Coating Adhesion- Metallographical Preparation- Hardness Testing- Chemical Composition (e.g. GDOS)- Wear Testing- Corrosion Testing

2.2 Non-destructive Test Methods:- Coating Thickness Measurements- Ultrasonic Testing- Thermal Imaging

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History of Thermal Spraying:

Dr. Max U. SchoopBorn: April 10, 1870 in Frauenfeld (TG)Deceased: February 20, 1956 in Zürich(Drawing from 1920)

from: Tagungsunterlagen zum 3. Kolloquium über Hochgeschw.-Flammspritzen, Dr. K. Kirner

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Classification of Thermal Spraying(according EN 657)

Thermal spraying

Thermalsprayingby liquid

Thermal spraying by gas

Thermal spraying byelectric gas discharge

Molten bathspraying

Flamespraying

Detonationspraying

High velocityflame spraying

Powder flamespraying

Wire flamespraying

Arc spraying Plasma spraying

Plasmaspraying in air

Liquid stabilisedplasma spraying

Plasma sprayingin chambers

Laser spraying

Thermalsprayingby beam

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Different Thermal Spray Torches:

from: Stan Grainger, "Funktionelle Beschichtungen in Konstruktion und Anwendung"

Flame Spraying

Detonation GunSpraying

High VelocityOxygen Fuel

Spraying Plasma Spraying

Electric Arc Spraying

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Thermal Spraying by Principle:molten droplets

"clamping"

substrate

"local alloying"

voids

heat powder+ =

v

time

Temperature

RT

T melting

T substrate

T boiling

dT/dt = 10 K/s6

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Thermal Spraying in „Reality“:Powder Splats Coating / Substrate

Ref 1: Edward J. Kubel Jr. in Adv. Mat. & Proc. 12/90Ref 2: R.C. Dykhuizen in Journ. of Therm. Spr. Techn. Vol 3, No. 4 (94)Ref 3: M. Vardelle et al. in Journ. of Therm. Spr. Techn. Vol 4, No. 1 (95)

1) 2)

3)

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Thermally Sprayed Cr2O3-Coatings (created by different processes)

flame sprayed plasma sprayed HVOF sprayed

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2. Characterization Techniques

2.1 Destructive Test Methods

2.1.1. Coating Adhesion (EN 582, ISO/DIS 14916)

2.1.2. Metallographical Preparation for LM, SEM, etc.

2.1.3. Hardness Testing

2.1.4. Chemical Analysis (e.g. GDOS, and others)

2.1.5. Wear Testing

2.1.6. Corrosion Testing

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Tensile testingmachine :Epprecht: 250 kN

Tensile AdhesiveStrength Test(EN 582, ISO/DIS 14916)

Frame for glueing 5 samples(left: empty, right: with samples)

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MetallographicalPreparationInvestigation of:Coating thickness, coatingmorphology (structure, phases,porosity), bonding to substrate,micro hardness

Steps:1. Sectioning2. Embedding (organic binder, event. vacuum infiltration)3. Grinding (e.g. SiC 180 to 1200)4. Polishing (6, 3, 1, 1/4 µm)5. Cleaning6. Event. sputtering for interference layer contrast (e.g. ZnSe, ZnTe)7. Electrolytic -, chemical etching8. Investigation (LM, SEM) � Interpretation

from: DVS 2310-1 Merkblatt

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Hydroxyapatite Coatings forBiomedical Applications:

atmosphericplasma sprayed

vacuumplasma sprayed

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Hardness Testing� ISO 4516 Metallic and related coatings; Vickers and Knoop

microhardness tests� ISO 6506 Metallic materials; Hardness test; Brinell test� ISO 6507-1 Metallic materials - Vickers hardness test - Part 1:

Test method� ISO 6507-2 Metallic materials - Vickers hardness test - Part 2:

Verification of testing machines� ISO 6507-3 Metallic materials - Vickers hardness test - Part 3:

Calibration of reference blocks� ISO 6508 Metallic materials; Hardness test; Rockwell test

(scales A - B - C - D - E - F - G - H - K)

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Example of Microhardness Teston a Thermally Sprayed Coating

HV � 0.1891 x F/d2

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Chemical Analysis

� X-Ray Fluorescence Analysis (XRF)� Glow Discharge Optical Spectroscopy (GDOS)� Mass Spectrometry (MS)� Energy Dispersive X-Ray Analysis (EDX)� Electron Probe Micro Analysis (EPMA)� Transmission Electron Microscopy (TEM)� and many others ...

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Glow Discharge Optical EmissionSpectroscopy GDO(E)S

Glow Discharge ...

...Optical Emission Spectroscopy

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I

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0.1 nm

1 nm

10 nm

100 nm

1 µm

1.0 ppm 100 ppm 1% 100%

10 µm

Surface

Bulk

Concentration

Info

rmat

ion

Dep

th

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Comparison of Different MethodsEigenschaften AES SIMS ESCA ESMA SNMS GDOS

erfassbarerTiefenbereich in nm

1 - 100ohne

Zerstäubung

0,3 - 103

ohneZerstäubung

1 - 100ohne

Zerstäubung

Querschliff 0,5 - 104 1 - 105

Informationstiefe innm

1 - 6 0,5 - 1 0,5 - 10 1000 1 - 2 mitZerstäubung

1 - 100Tiefenauflösung in% der abgetragenen

Tiefe

2 nmohne

Zerstäubung

10 nmmit

Zerstäubung

0,5 nmohne

Zerstäubung

0,1 nm 10 7 - 12

TiefenprofilanalysetechnischerSchichten

1 - 2 µm mitZerstäubung;

oderQuerschliff

> 10 µm mitZerstäubung;Querschliff

1 µm mitZerstäubung;Querschliff

Querschliff Zerstäubung indie Tiefe5 - 10 µm

Zerstäubung indie Tiefe

40 - 150 µmmater. abh.

laterale Auflösung 0,2 µm 0,3 µm 200 µm 1 µm 20 µm 2,5 - 8 mmSimultananalyse keine keine keine keine keine max. alle

Elementetypische

Nachweisgrenzenin %

element-abhängig

0,1 - 5

teilweise bis10-4

0,1 - 1 0,1 - 10-3 0,1 - 10-4 10-2 - 10-4

Nachweis leichterElemente

> 0,1 atom %und Z � 3

alleeinschliesslich

H

alle ohne H nicht unter0,1 %

alleeinschliesslich

H

alleeinschliesslich

HQuantitative

Messungnicht sehr

genaunur in

homogenerMatrix

� 5 %verschiedene

Elemente

leichteElemente

schwierig bisunmög.

Quantifizierung Quantifizierung

AES = Auger Electron SpectroscopySIMS = Secondary Ion Mass SpectroscopyESCA = Electron Spectroscopy for Chemical AnalysisESMA = Elektronenstrahl Mikroanalyse = EPMA = Electron Microprobe AnalysisSNMS = Secondary Neutral Mass SpectroscopyGDOS = Glowdischarge Optical Spectroscopy

Ref. H. Böhm, Oberflächen Werkstoffe, Nr.4/94

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• Quality control for different coating systems(e.g. car industry)

• Galvanic coatings• Thin films (Semiconductor industry)• Paintings• Thermal Spraying• Diffusion zones• and many others ...

Typical Applications of GDOS:

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05

1015202530354045

Intensity (Volt)

Con

cent

ratio

n (%

)

AluminumCast ironSteelBrass

Quantitative Calibration of SiContent in Different Matrices

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TiN + TiCN on Steel

0

10

20

30

40

50

60

70

80

90

100

0.0 2.0 4.0 6.0 8.0 10.0 12.0

Tiefe in µm

Kon

zent

ratio

n in

%G

Ti

Steel

C

N Fe

Ti N

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Paintings on Tinplate

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GDOES... is a quantitative chemistry analysis method... for conductive and non conductive materials (RF)... for high concentration range (ppm ...100 %)... offers good resolution in depth (nm)... offers good integration in lateral size (spot diameter)... offers fast response (1 ... 10 µm/Min.)... up/down to 100‘s of microns... analysis of all elements (H...U) simultaneously... keeps substrate temperature low... needs no wet chemistry

Advantages

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Some Wear Testing StandardsASTM G 32: Test Method for Cavitation Erosion Using Vibratory

Apparatus (1992)

ASTM G 65: Test Method for Measuring Abrasion Using the DrySand/Rubber Wheel Apparatus (1994)

ASTM G 73: Liquid Impingement Erosion Testing (1993)

ASTM G 75: Test Method for Determination of Slurry Abrasivity(Miller Number) and Slurry Abrasion Response ofMaterials (SAR Number) (1995)

ASTM G 76: Conducting Erosion Tests by Solid Particle ImpingementUsing Gas Jets (1995)

ASTM G 99: Test Method for Wear Testing with a Pin-on-DiskApparatus (1995)

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aus: DIN 50320 Verschleiss; Begriffe, Systemanalyse von Verschleissvorgängen, Gliederung des Verschleissgebietes

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ASTM G 32 - 92:Test Method forCavitationErosion UsingVibratoryApparatus

Bestimmung derKavitations-erosion anvibrierendenProben

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Test Method for MeasuringAbrasion Using the DrySand/Rubber WheelApparatus

Richtlinien für dieDurchführung vonAbriebversuchen mitTrockensand undrotierendem Gummirad

ASTM G 65 - 94:

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Determination of SlurryAbrasivity (Miller Number)and Slurry AbrasionResponse of Materials(SAR Number)

Bestimmung derSchleifwirkung vonSchlamm nach demNummernsystem vonMiller

ASTM G 75 - 95:

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100 1000 100000,1

1

10

100Volumetricmaterial losstestedaccording toASTM G 75as a functionof materialshardness

Ref. WF-Project, O. Brandt, St. Siegmann

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Bedienpult

PulverförderAbsetzbecken

Erosionskammer

HorizontaleFührungs-schiene

Höhen-verstellungvergl.Abb. 6

Proben-halterungmit Ver-formungs-einrichtungAbb. 8

VertikaleFührung

PneumatischerSchliesser

MischkopfAbb.2

Hochdruck-pumpen-anschluss

Erosion Test Equipment

Ref. L. Kirchhoff, O. Brandt

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ASTM G 99: Pin-on-Disk Tribometer

Rotation speed: 0.03 to 500 rpmForces: 1 to 60 NStandard loads: 1, 2, 5, 10 NDisk dimensions: r = 60 mm,

h = 15 mm

(compatible with DIN 50324)

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Some Technical Corrosion Tests

prEN 4437: Test Method of Salt Spray(Fog) Testing

EN ISO 6988: Sulfur dioxide test with generalcondensation of moisture

ASTM B 368: Acetic Acid-Salt Spray (Fog)Testing (CASS Test)

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CorrosionTesting

Fig: O. Brandt

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Results from Corrosion Tests

Same coating material:porous (atmospheric

sprayed) and showinginterface corrosion

dense (vacuum plasmasprayed)

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2.2. Non-destructive Test Methods

2.2.1. Coating Thickness Measurements

2.2.2. Chemical Composition (see also 2.1.4)

2.2.3. Ultrasonic Testing

2.2.4. Thermal Imageing

2. Characterization Techniques

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Standards for Coating Thickness Measurements1. ENV 1071-2 Determination of coating thickness by the cap grinding method2. ISO 1463 Measurement of coating thickness; Microscopical method3. ISO 2064 Definitions and conventions concerning the measurement of thickness4. ISO 2177 Measurement of coating thickness; Coulometric method by anodic

dissolution5. ISO 2178 Measurement of coating thickness; Magnetic method6. DVS 2303-1 Non-destructive testing of thermally sprayed coatings, thickness

measurements7. ISO 2360 Measurement of coating thickness; Eddy current method8. ISO 2808 Paints and varnishes - Determination of film thickness9. ISO 3497 Measurement of coating thickness; X-ray spectrometric methods

10. ISO 3543 Measurement of thickness; Beta backscatter method11. ISO 3868 Measurement of coating thicknesses; Fizeau multiple-beam

interferometry method; Mehrstrahlinterferometer-Methode nach Fizeau12. ISO 3882 Review of methods of measurement of thickness13. ISO 4518 Measurement of coating thickness; Profilometric method14. ISO 9220 Measurement of coating thickness; scanning electron

microscope method

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Ultrasonic Testing on Coatings(by principle)

from: Krautkrämer, Zerstörungsfreie Werkstoffprüfung mit Ultraschall, Einführung in die Grundlagen

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Ultrasonic Picture of Coatingand Adhesion Defects

Ultrasonic picture(from back side)

Optical picture(from top side)

corrosion

roughnessdefect

metallicinclusions

ceramic groundlayer

Gradient:metal /ceramic

substrate

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Ref. DACS / IBF

Thermal Imagingon ThermallySprayedCoatings(by principle)

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Investigation by Thermal Imaging

Ref. DACS / IBFRef. EMPA

Optical picture Thermographic picture

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Conclusions: Characterization

Many standardized test methods available

• for coating development

• for coating quality assurance

• for characterizing coating failure

but still needsbetter predictability of coating reliability

Research:as much as

possible

Industry:as much asnecessary