I Introduction ................................................. 1
1 Introduction to Nano-crystalline Material .................... 3
1.1 Introduction ............................................ 3
1.2 Mechanical properties of NC material .................... 4
1.2.1 Elastic properties ............................... 4
1.2.2 Hardness and strength ............................ 6
1.2.3 Ductility ........................................ 7
1.2.4 Fatigue and fracture ............................. 7
1.3 Production of NC structure .............................. 8
1.3.1 Electrodeposition ................................ 9
1.3.2 Inert-gas condensation .......................... 10
1.3.3 Solid state processing methods .................. 11
1.4 Measurement techniques ................................. 12
1.4.1 Crystallography ................................. 12
1.4.2 Microscopy ...................................... 12
1.5 Application of NC material ............................. 13
1.5.1 Nanotechnology in automotive applications ....... 14
1.5.2 Industrial applications of nanocomposite
coatings ........................................ 14
1.5.3 Biomechanics and prosthesis ..................... 14
1.6 Conclusion ............................................. 15
Bibliography ................................................ 19
2 Introduction to Cold Spray Coating .......................... 19
2.1 Introduction ........................................... 19
2.2 Cold spray coating process ............................. 21
2.2.1 Principal process parameters .................... 22
2.3 Advantages of cold spray coating ....................... 27
2.4 Applications ........................................... 28
2.4.1 Wear resistance ................................. 29
2.4.2 Corrosion protection ............................ 29
2.4.3 Repair of damaged components .................... 29
2.4.4 Coating and NC .................................. 29
2.5 Effect of cold spray coating on fatigue strength ....... 30
2.6 Conclusion ............................................. 31
Bibliography ................................................ 32
3 Shot Peening and Surface Nano-crystallization ............... 35
3.1 Introduction ........................................... 35
3.2 Shot peening control parameters ........................ 36
3.2.1 Almen intensity and saturation curve ............ 37
3.2.2 Surface coverage ................................ 37
3.3 Shotpeening process to obtain nano-structured surface .. 38
3.4 Fatigue behavior of surface nanocrystallized material
obtained by shot peening ............................... 39
3.5 Numerical simulation of shot peening ................... 39
3.6 Conclusion ............................................. 41
Bibliography ................................................ 42
II Numerical simulations ...................................... 45
4 Critical velocity calculation ............................... 47
4.1 Introduction ........................................... 47
4.2 Experimental measurement of CV ......................... 48
4.3 Numerical simulation for CV assessment: a review ....... 50
4.4 A new approach to find the CV by FEM ................... 52
4.4.1 FEM model ....................................... 52
4.4.2 Boundary condition .............................. 52
4.4.3 Material model .................................. 53
4.4.4 Damage control .................................. 54
4.4.5 Adiabatic shear instability ..................... 55
4.4.6 Mesh convergence study .......................... 56
4.4.7 Challenges in finding the shear instability ..... 57
4.4.8 Discrete numbers and Sobolev space .............. 57
4.4.9 Algorithm of the process ........................ 58
4.4.10 Denoising Technique ............................. 60
4.5 Evaluation of the numerical model ...................... 61
4.5.1 Particle deformation ............................ 62
4.5.2 Comparison of CV ................................ 66
4.6 Effect of the process parameters on CV ................. 67
4.6.1 Temperature of the particles .................... 67
4.6.2 Effect of Shot peening before coating ........... 69
4.7 Conclusion ............................................. 69
Bibliography ................................................ 72
5 Numerical assessment ot the coated surface .................. 75
5.1 Introduction ........................................... 75
5.2 Introduction to the FEM model .......................... 76
5.2.1 Particle size ................................... 77
5.2.1.1 Single shot model ...................... 77
5.2.1.2 Particle size considerations ........... 77
5.2.2 Particle velocity ............................... 79
5.2.2.1 Single shot model ...................... 79
5.2.2.2 Particle velocity considerations ....... 81
5.2.3 Particle temperature ............................ 83
5.2.3.1 Single particle model .................. 83
5.2.3.2 Particle temperature consideration ..... 84
5.3 Numerical model ........................................ 85
5.3.1 Obtaining the results ........................... 85
5.3.2 Process implementation .......................... 86
5.4 Results of multi-impact model .......................... 86
5.5 Conclusion ............................................. 90
Bibliography ................................................ 91
III Experimental analysis ..................................... 93
6 Microstructural analysis and coating characterization ....... 95
6.1 Introduction ........................................... 95
6.2 XRD measurements ....................................... 96
6.3 Grain size measurement ................................. 97
6.3.1 The method of Voigt function .................... 98
6.4 Experimental verification .............................. 99
6.5 Cold spray coating parameters ......................... 102
6.5.1 High pressure coating .......................... 104
6.5.2 Low pressure coating ........................... 104
6.6 Specimens and coated materials ........................ 105
6.6.1 Substrate ...................................... 105
6.7 Coating characterization .............................. 106
6.7.1 Coating parameters ............................. 106
6.7.2 Coating microstructural analysis ............... 106
6.7.3 Residual stress and micro-hardness
measurement .................................... 106
6.8 Severe shot peening ................................... 108
6.9 Application of grain size measurement to the treated
samples ............................................... 110
6.9.1 Coated samples ................................. 110
6.9.2 Samples treated by combined shot peening and
cold spray coating ............................. 110
6.10 Conclusion ............................................ 113
Bibliography ............................................... 114
7 Fatigue test ............................................... 117
7.1 Introduction .......................................... 117
7.2 Testing machine setup ................................. 117
7.3 Test specimen ......................................... 120
7.4 test machine calibration .............................. 123
7.5 Fatigue tests ......................................... 123
7.6 Results ............................................... 125
7.6.1 S-N diagram .................................... 126
7.6.2 Fractography ................................... 126
7.7 Conclusion ............................................ 126
Bibliography ............................................... 128
IV Conclusion ................................................ 131
8 Conclusion ................................................. 133
8.1 Results and discussion ................................ 133
8.2 Future work ........................................... 135
Appendix ...................................................... 137
A Code for Critical velocity ................................. 139
A.1 Python ................................................ 139
A.2 Matlab ............................................... 151
B Code for peening effect model .............................. 155
B.l Python code for making the model ...................... 155
B.2 Code for obtaining the result ......................... 160
C Grain size measurement ..................................... 163
C.1 Matlab code for grain size ............................ 163
| 
