vii TABLE OF CONTENTS CHAPTER TITLE PAGE DECLARATION DEDICATION ACKNOWLEDGEMENTS ABSTRACT ABSTRAK TABLE OF CONTENTS LIST OF TABLES LIST OF FIGURES LIST OF SYMBOLS / ABBREVIATIONS LIST OF APPENDICES ii iii iv v vi vii xii xiv xviii xxi
viii 1 INTRODUCTION 1 1.1 Background of the Study 1 1.2 Problem Statement 3 1.3 Objective of the Study 4 1.4 Scope of the Study 5 1.5 Structure of the Thesis 6 2 LITERATURE REVIEW 7 2.1 Introduction 7 2.2 Shape Memory Alloys (SMAs) 8 2.3 Nickel Titanium Shape Memory Alloys (NiTi 9 SMAs) 2.3.1 General Principles 9 2.3.2 Thermomechanical Behavior 10 2.3.3 Properties of NiTi SMA 12 2.4 Applications of NiTi SMAs 17 2.5 Coating Techniques 17 2.5.1 Physical Vapor Deposition (PVD) 18 Technique 2.5.1.1 Introduction of PVD Technique 18 2.5.1.2 Magnetron Sputtering Technique 19 2.6 Post-sputtering Annealing Process 22
ix 2.7 Effect of Post-sputtering Annealing Process on 23 Structure and Tribological Properties of NiTi SMA Coating 2.8 Stainless Steel Material 28 2.8.1 Type of Stainless Steel 28 2.9 Stainless Steel 316L 30 2.9.1 Properties of Stainless Steel 316L 31 2.9.2 Composition of Stainless Steel 316L 35 2.10 Characterization Methods of NiTi SMA Coating 37 2.10.1 Thermal Properties 38 2.10.2 Structural, Surface and Composition 40 Analysis 2.10.3 Mechanical and Tribological Properties 49 3 RESEARCH METHODOLOGY 55 3.1 Introduction 55 3.2 Flow Chart of Research Activities 56 3.3 Substrate Materials 57 3.3.1 Preparation of Stainless Steel 316L 57 Substrate 3.4 Sputtering Physical Vapor Deposition (PVD) 59 Technique
x 3.4.1 Sputtering Process Parameters 60 3.5 Post-sputtering Annealing Process 61 3.6 Coating Characterisation Techniques 62 3.6.1 Cross-sectioned Sample Preparation 62 3.6.2 Thermal Analysis Using the Differential 63 Scanning Calorimetry (DSC) 3.6.3 Structural, Surface and Composition 64 Analysis 3.6.4 Mechanical and Tribological Properties 67 4 RESULTS AND DISCUSSION 71 4.1 Introduction 71 4.2 Substrate Material Characterization 72 4.2.1 Composition Analysis of 316L Stainless 72 Steel Substrate 4.2.2 Composition Analysis of Silicon Substrate 74 4.3 Composition Analysis of Unannealed NiTi 75 Coating 4.4 Cross-sectioned of Unannealed NiTi SMA 76 Coating Sample 4.5 Thermal Properties 79 4.6 Phase and Crystallographic Plane 80
xi 4.6.1 Unannealed NiTi SMA Coating 80 4.6.2 Annealed NiTi SMA Coating 82 4.7 Surface Morphology and Roughness 85 Measurement 4.7.1 Surface Roughness Tester 85 4.7.2 Atomic Force Microscope (AFM) 86 4.8 Mechanical and Tribological Properties 91 4.8.1 Rockwell C Adhesion Test 91 4.8.2 Pin-on-disc Wear Test 95 4.8.3 Nanoindentation 102 5 CONCLUSION AND RECOMMENDATIONS FOR FUTURE WORK 106 5.1 Conclusion 106 5.2 Recommendations 107
xii LIST OF TABLES TABLE NO TITLE PAGE 2.1 NiTi mechanical properties 25 2.2 Mechanical properties of 316L stainless steels 32 2.3 Physical properties of 316L stainless steel 33 2.4 Composition of 316 and 316L stainless steel 36 2.5 Rockwell hardness scales 50 3.1 Parameters used for grinding process 58 3.2 Parameters of post-sputtering annealing process 61 3.3 Parameters of grazing angle X-ray diffraction (GAXRD) 65 3.4 Parameters of surface roughness tester 66 3.5 Parameters of atomic force microscope (AFM) 67 3.6 Parameters of Rockwell C adhesion test 68 3.7 Parameters of pin-on-disc wear test 69 3.8 Parameters of nanoindentation 70 4.1 Chemical composition of 316L stainless steel substrate 73
xiii 4.2 Chemical composition of unannealed NiTi coated on silicon substrate 4.3 The surface roughness Ra and Ra (average) of NiTi SMA coated on the 316L stainless steel at different parameters 4.4 The Ra and Rms values for the unannealed and annealed 600 C for 30 minutes NiTi SMA coating samples at 1.0 x 1.0 µm² scan area 4.5 The results obtained from the nanoindentation test on the unannealed and annealed 600 C for 30 minutes NiTi SMA coating 76 86 90 103
xiv LIST OF FIGURES FIGURE NO TITLE PAGE 1.1 Structure of the thesis 6 2.1 Martensitic transformation and hysteresis (= H) upon a change of temperature. A s = austenite start, A f = austenite finish, M s = martensite start, M f = martensite finish and M d = highest temperature to strain-induced martensite. Gray area = area of optimal superelasticity 2.2 Typical stress-strain curves at different temperatures relative to the transformation showing (a) Austenite, (b) Martensite, (c) Pseudoelastic behavior 2.3 Transformation from the austenite to the martensite phase and shape memory effect 2.4 The procedures are very similar: (a) starting from martensite, (b) adding a reversible deformation for the one-way effect or severe deformation with an irreversible amount for the two-way, (c) heating the sample and (d) cooling it again 2.5 Schematic presentation of lattice structure changes caused by outer stress in stainless steel or superelastic NiTi alloy 10 11 13 15 16
xv 2.6 Principle of sputter deposition process 21 2.7 The different grades of damages to classify the indentation patterns in the Rockwell adhesion test, after 26 2.8 Typical DSC curve 39 2.9 Schematic diagram of the SEM 41 2.10 Some electrons and X-rays ejected from the sample by the incident beam 2.11 Fourteen (14) Bravais lattice patterns, 3-dimensional (3D) 42 44 2.12 Working principle of XRD 45 2.13 Surface characteristic 46 2.14 A schematic diagram of atomic force microscope (AFM) 48 2.15 Working principle of Rockwell hadrness testing 51 2.16 Schematic diagram of Pin-on-disc tester 52 2.17 Schematic diagram of nanoindenter 53 2.18 Load-displacement curve for an instrumented nanoindentation test 54 3.1 Flow chart of research activities 56 3.2 Mechanism of sputtering process 60 4.1 EDX spectra of 316L stainless steel substrate 72 4.2 EDX spectra of silicon substrate 74
xvi 4.3 EDX spectra of unannealed NiTi coated on silicon substrate 4.4 The measurement of the unannealed NiTi SMA coating thickness by doing a cross-section process on 316L stainless steel. (a) coating layer, (b) interlayer and (c) substrate material 4.5 EDX spectra of (a) coating layer, (b) interlayer and (c) substrate material 75 77 78 4.6 DSC curve of unannealed NiTi SMA coating 80 4.7 XRD pattern of unannealed NiTi SMA coating 81 4.8 XRD pattern of the annealed NiTi SMA coatings at temperature 550 C for duration of (a) 30 and (b) 60 minutes 4.9 XRD pattern of the annealed NiTi SMA coatings at temperature 600 C for duration of (a) 30 and (b) 60 minutes 4.10 The AFM typical two-dimensional (2D) surface morphology of the (a) unannealed and (b) annealed at 600 C for 30 minutes samples 4.11 The AFM typical three-dimensional (3D) surface morphology of the (a) unannealed and (b) annealed at 600 C for 30 minutes samples 4.12 The surface morpology of Rockwell C adhesion test with different parameters, (a) unannealed, (b) annealed at 550 C for 30 minutes, (c) annealed at 550 C for 60 minutes, (d) annealed at 600 C for 30 minutes and (e) annealed at 600 C for 60 minutes under the optical observation 83 84 88 89 92
xvii 4.13 The surface morpology of Rockwell C adhesion test at high magnification image using SEM at different parameters; (a) unannealed, (b) annealed at 550 C for 30 minutes, (c) annealed at 550 C for 60 minutes, (d) annealed at 600 C for 30 minutes and (e) annealed at 600 C for 60 minutes 4.14 Wear tracks morpologies for (a) unannealed, (b) 550 C for 60 minutes and (c) 600 C for 30 minutes under the optical observation 4.15 The wear width measurement and chemical composition analysis of unannealed (a, b) and annealed ((c, d) 550 C (60 min) and (e, f) 600 C (30 min)) by SEM 4.16 The pin-on-disc results for different type of samples; unannealed, 550 C (60 min) and 600 C (30 min) 4.17 Mechanical proeprties versus indentaion depth (a) H versus penetration depth (b) E versus penetration depth and (c) H/E Ratio versus penetration depth 94 96 98 101 104
xviii LIST OF SYMBOLS/ABBREVIATIONS A f - Austenite Finish Temperature AFM - Atomic Force Micriscope Amrec - Advance Materials Research Centre Ar - Argon A s - Austenite Start Temperature ASTM - American Society for Testing and Materials BCC - Body Centered Cubic BSE - Backscattered Electrons Cr - Chromium CVD - Chemical Vapour Deposition d - Diameter DC - Direct Current DSC - Differential Scanning Calorimetry E - Young s Modulus EDX/EDAX - Energy Dispersive X-ray Spectroscopy FCC - Face Centered Cubic Fe - Iron
xix GDS - Glow Discharge Spectroscopy GAXRD - Grazing Incidence Angle X-ray Diffraction GPa - Giga-Pascal H - Hardness H/E - Ratio of Hardness to Young s Modulus IBAD - Ion-Beam Assisted Deposition mbar - Milibar M d - Highest Temperature To Strain-Induced Martensite M f - Martensite Finish Temperature MEMS - Micro-Electro-Mechanical System MPa - Mega-Pascal M s - Martensite Start Temperature Ni - Nickel NiTi - Nickel Titanium OM - Optical Microscopy PDF - Powder Diffraction File PECVD - Plasma Enhanced Chemical Vapour Deposition PVD - Physical Vapour Deposition Ra - Average Roughness RF - Radio Frequency RMS - Root Mean Square Roughness SE - Superelasticity / Secondary Electrons SEM - Scanning Electron Microscopy
xx Si - Silicon SiC - Silicon Carbide SMA - Shape Memory Alloy SMAs - Shape Memory Alloys SME - Shape Memory Effect Ti - Titanium TiN - Titanium Nitride TTRs - Transformation Temperatures VDI - Verein Deutscher Ingenieure XRD - X-ray Diffraction 2D - Two-Dimension 3D - Three-Dimension
xxi LIST OF APPENDICES APPENDIX TITLE PAGE A Powder diffraction file (PDF) 117 B XRD pattern list 119 C GDS composition analysis (316L stainless steel) 120 D Pin-on-disc measurement 121