Experimental and Numerical Investigation into the Adhesion of PVD Coatings on Minting Dies

158 Pages·2013·5.74 MB·English

Experimental and Numerical Investigation into the
Adhesion of PVD Coatings on Minting Dies
by
Jason Tunis, B.Eng.
A thesis submitted to
the Faculty of Graduate Studies and Research
in partial fulfillment of the requirements for the
degree of Master of Applied Science
Ottawa-Carleton Institute for Mechanical and Aerospace Engineering
Department of Mechanical and Aerospace Engineering
Carleton University
Ottawa, Ontario
Canada
January 2012©
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Abstract
This thesis reports on the adhesion characterization of a PVD coating deposited onto mirror
polished and laser frosted minting die surfaces. Experimental and numerical methods are
both used to study the adhesion of the PVD coating. The Rockwell-C indentation, the
stepped indentation, and the scratch adhesion testing methods are used to experimentally
examine the coating adhesion. Finite element analyses of the stepped indentation and scratch
adhesion tests are performed using critical loads determined from experimental testing. The
analyses are performed to determine the stresses produced at the coating-substrate interface
prior to coating adhesion failure and characterize the coating adhesion.
The coating applied to a mirror surface and to two of the four laser frosted surfaces passed
the Rockwell-C indentation adhesion test. The stepped indentation adhesion testing
determined the maximum survivable indentation load without coating adhesion failure for
three of the five tested surfaces. The scratch test was found to be a suitable adhesion test
method for all the coated surfaces except the roughest laser frosted surface.
The indentation and scratch simulations found that large compressive, shearing, and opening
stresses were present at the coating-substrate interface in the regions where coating
delamination was observed during experimental testing. The value of the compressive,
opening, and shear critical stresses found during finite element simulation of the indentation
and scratch tests are in reasonable agreement. These stress components provide good
quantification of the coating adhesion strength.
Acknowledgements
I wish to express my sincere appreciation and gratitude to my thesis supervisor, Professor
Xin Wang, for his constant support and encouragement. Without his guidance and patience
this thesis would not have been possible.
I would like to thank Dr. Xianyao Li and the staff at the Royal Canadian Mint for providing
direction and technical assistance during my work at the Mint.
Iam grateful for the financial support from the Ontario Centre for Excellence and the Royal
Canadian Mint.
Finally, I would like to thank my family andfriends for their support and encouragement.
Table of Contents
ABSTRACT.........................................................................................................................Ill
ACKNOWLEDGEMENTS................................................................................................IV
TABLE OF CONTENTS.....................................................................................................V
LIST OF TABLES_____________________________________________________ VIII
LIST OF FIGURES...........................................................................................................IX
LIST OF SYMBOLS........................................................................................................XIV
CHAPTER 1: INTRODUCTION........................................................................................1
1.1 Thesis Objectives.............................................................................................................................3
1.2 Thesis Outline...................................................................................................................................3
CHAPTER 2: BACKGROUND AND LITERATURE REVIEW....................................5
2.1 PVD Coating Process.....................................................................................................................5
2.2 Laser Frosting Process................................................................................................................6
2.3 Adhesion of Thin-Film Systems................................................................................................7
2.4 Indentation Adhesion Test.........................................................................................................8
2.4.1 Experimental Indentation Adhesion Testing...........................................................9
2.4.2 Finite Element Analysis of indentation adhesion testing.......................................10
2.5 Scratch Adhesion Test...............................................................................................................13
2.5.1 Experimental Scratch Adhesion Testing................................................................13
2.5.2 Finite Element Analysis of scratch adhesion testing.............................................14
2.6 Summary.............................................................................................................................................16
CHAPTER 3: EXPERIMENTAL TESTING OF COATING ADHESION..................28
3.1 Sample Preparation......................................................................................................................28
3.2 Rockwell-C Indentation Adhesion Test...........................................................................28
3.2.1 Experimental Setup...............................................................................................29
3.2.2 Procedure.............................. 29
3.2.3 Results...................................................................................................................30
3.3 Stepped Indentation Adhesion Test.....................................................................................32
v
3.3.1 Experimental Apparatus and Procedure..............................................................32
3.3.2 Results...................................................................................................................33
3.4 Scratch Adhesion Test...............................................................................................................35
3.4.1 Experimental Apparatus.......................................................................................35
3.4.2 Procedure.............................................................................................................35
3.4.3 Results...................................................................................................................36
3.5 Summary............................................................................................................................................38
CHAPTER 4: TWO-DIMENSIONAL AXISYMMETRIC INDENTATION
ADHESION TEST SIMULATION....................................................................................62
4.1FEM Model Setup, Geometry, and Boundary Conditions........................................63
4.1.1 Indenter Geometry................................................................................................63
4.1.2 Die Geometry........................................................................................................63
4.2 Determination of Material and Interface Properties..............................................64
4.2.1 Indenter Properties...............................................................................................64
4.2.2 Substrate Properties.............................................................................................64
4.2.3 Coating Properties................................................................................................66
4.2.4 Interface Properties..............................................................................................66
4.2.5 Mesh Design.........................................................................................................67
4.3 Stress Transformation.............................................................................................................68
4.4 Results...............................................................................................................................................69
4.4.1 Convergence Analysis...........................................................................................69
4.4.2 Deformed Geometry...............................................................................................70
4.4.3 Von Mises Stress Results.......................................................................................70
4.4.4 Radial Stress Results..............................................................................................71
4.4.5 Hoop Stress Results...............................................................................................71
4.4.6 Opening Stress Results..........................................................................................72
4.4.7 Shear Stress Results...............................................................................................72
4.5 Summary............................................................................................................................................73
CHAPTER 5: THREE-DIMENSIONAL SCRATCH ADHESION TEST
SIMULATION.....................................................................................................................99
5.1FEM Model Geometry and Setup..........................................................................................99
5.1.1 Indenter Geometry and Properties......................................................................100
5.1.2 Die Geometry and Properties..............................................................................100
5.1.3 Interface Properties............................................................................................100
5.1.4 Mesh Design.......................................................................................................101
5.2 Results.............................................................................................................................................102
5.2.1 Stress Transformation.........................................................................................102
5.2.2 Convergence Analysis.........................................................................................104
5.2.3 Von Mises Stress Results............................................................... 105
5.2.4 Opening Stress Results.......................................................................................106
5.2.5 Shear Stress Results in the Interface Plane.........................................................106
5.2.6 Normal Stresses Results in the Interface Plane...................................................107
5.3 Summary...........................................................................................................................................107
CHAPTER 6: CONCLUSIONS AND RECOMMENDATIONS...................................124
6.1 Conclusions...................................................................................................................................124
6.2 Recommendations.......................................................................................................................126
APPENDIX A................................................................................ 127
APPENDIX B.....................................................................................................................132
REFERENCES..................................................................................................................139
vii
List of Tables
Table 3.1: Rockwel-C adhesion test results..............................................................................40
Table 3.2: Summary of Rockwell-C adhesion test..................................................................41
Table 3.3: Stepped indentation delamination results for mirror surface dies........................42
Table 3.4: Stepped indentation delamination results for laser frosted surfaces....................43
Table 3.5: Scratch test data for the coating deposited on a mirror surface..............................44
Table 3.6: Scratch test data for the coating deposited on laser frosted surfaces...................45
Table 3.7: Summary of scratch adhesion test results...............................................................45
Table 4.1: Material properties of the simulated substrate.........................................................74
Table 4.2: Experimental indenation crater size.........................................................................74
Table 4.3: Simulated indentation crater size using ABAQUS and multiple strain hardening
exponent values...........................................................................................................................74
Table 4.4: Material properties of the simulated coating...........................................................75
Table 4.5: Convergence of the coating and substrate maximum opening and shear stresses
for the 15 kgf indentation simulation using the most refined model.......................................75
Table 4.6: Convergence of the coating and substrate maximum opening and shear stresses
for the 30 kgf indentation simulation using the most refined model.......................................75
Table 4.7: Important stress values for coating adhesion strength characterisation................76
Table 5.1: Convergence of maximum critical stress in the coating side of the interface.... 109
Table 5.2: Convergence of maximum critical stress in the substrate side of the interface.. 109
Table 5.3: Convergence of coating and substrate maximum stress value for the 2 layer
simulation...................................................................................................................................109
Table 5.4: Important stress values for coating adhesion strength characterisation 110
Table 5.5: Comparison of maximum stress results for the indentation and scratch simulation
of the PVD coating adhesion to a mirror surface....................................................................110
List of Figures
Figure 2.1: Test dies with three-quarter laser frosted surfaces............................................17
Figure 2.2: Laser frostings at 1000X magnification............................................................18
Figure 2.3: Schematic of indentation test causing coating adhesion failure (Lacombe, 2006)
18
Figure 2.4: Wilson Rockwell 3TT Twin Hardness Tester...................................................19
Figure 2.5: Rockwell-C adhesion test grading as defined by VDI Guideline 3198 (1991)... 20
Figure 2.6: (a) TiN 240 min deposition and 3.88 pm coating thickness, (b) Q N 240 min
2
deposition and 22.45 pm coating thickness, (c) CrN 60 min deposition and 5.08 pm coating
thickness (Heinke et al., 1995)...................................................................................................21
Figure 2.7: Radial and circular cracks at the indentation edge, of a H13 steel nitride for 3
hours and coated with TiN. The black arrow indicates a radial crack, while the white arrow
indicates a circular crack (Ribeiro, 2003)..................................................................................22
Figure 2.8: Top view of an indentation mark, or is the radial stress and is the tangential
00
stress (Pachler et al., 2007).........................................................................................................22
Figure 2.9: Axisymmetric finite element model of indentation adhesion test (Pachler, 2007)
........................................................................................................................ 23
Figure 2.10: Delamination failure modes (Benham et al., 1996)............................................23
Figure 2.11: Scratch adhesion test schematic (Lee, 1991).......................................................24
Figure 2.12: Teer Scratch Tester................................................................................................24
Figure 2.13: Schematic of the possible failures during scratch adhesion testing (Meneve et
al., 2001).......................................................................................................................................25
Figure 2.14: (a) TiN 1.54 pm coating thickness, 30-40 N load, (b) C^N 5.08 pm coating
thickness, 15-22 N load, (c) CrN 6.54 pm coating thickness, 20-30 N load (Heinke et al.,
1995).............................................................................................................................................26
Figure 2.15: Three-dimensional model for simulating the scratch adhesion test, (a) overall
model, (b) detail near the indenter tip (Li et al., 2006).............................................................27
Figure 3.1: Carl Zeiss Axiovert 200 Max inverted microscope fitted with Sony ExwaveHAD
video camera................................................................................................................................46