Preface ........................................................ XI
1. Introduction ................................................. 1
1.1. General Description ..................................... 2
1.2. Overview of Competitive Technologies .................... 4
1.2.1. Coating Characterization ......................... 4
1.2.2. Flame Spraying ................................... 5
1.2.3. Arc Wire Spraying ................................ 6
1.2.4. Plasma Spraying .................................. 6
1.2.5. Rapid Prototyping ................................ 7
1.2.6. Plasma Deposition Manufacturing .................. 8
1.2.7. Explosive Cladding ............................... 9
1.3. Concluding Remarks ..................................... 20
2. Impact Features of Gas Dynamic Spray Technology ............. 11
2.1. Impact Phenomena in GDS ................................ 11
2.1.1. Main Features ................................... 11
2.1.2. Rebound and Erosion Processes ................... 12
2.1.3. GDS Processes ................................... 16
2.2. One Particle Impact in GDS ............................. 17
2.2.1. Shear Localization Phenomenon ................... 17
2.2.2. Adiabatic Shear Instability in GDS .............. 22
2.2.3. Experiments Relating to Particle Impact ......... 29
2.3. Concluding Remarks ..................................... 35
3. Densification and Structure Formation of the Particulate
Ensemble .................................................... 37
3.1. Identification of Various Phenomena .................... 37
3.2. Observations of GDS Consolidated Materials ............. 40
3.3. Energy Requirements for GDS Shock Consolidation ........ 45
3.3.1. Plastic Deformation Energy ...................... 45
3.3.2. Microkinetic Energy ............................. 46
3.3.3. Frictional Energy ............................... 47
3.3.4. Adiabatic Shear Band Formation Energy ........... 48
3.3.5. Defect Energy ................................... 49
3.4. Computation of ASB Energy Parameters ................... 49
3.5. Shear Localization During Particle Shock
Consolidation .......................................... 50
3.6. Impact Powder Compaction Model ......................... 51
3.7. Behavior of Consolidating Powder Under Compression ..... 54
3.7.1. Constitutive Function ........................... 54
3.7.2. Yield Function and Property Estimations ......... 55
3.8. Consolidation Parameters of GDS and Shear
Compression ............................................ 56
3.8.1. Estimation of Compaction Parameters ............. 57
3.8.1.1. GDS Experiments ........................ 57
3.8.1.2. Shear Compaction Modeling .............. 57
3.9. Modeling Results and Discussion ........................ 58
3.9.1. ASB Width Evaluation ............................ 58
3.9.2. Yield Stress of Powder Material ................. 59
3.10.Concluding Remarks ..................................... 60
4. Low-Pressure GDS System ..................................... 65
4.1. State-of-the-Art Cold Spray Systems .................... 65
4.2. State-of-the-Art Powder Feeding Systems ................ 70
4.3. Modification of the Low-Pressure Portable GDS System ... 73
4.4. An Industrial Low-Pressure Portable GDS System ......... 77
5. General Analysis of Low-Pressure GDS ........................ 79
5.1. Statement of Problem ................................... 79
5.2. Experimental Procedure ................................. 80
5.3. Experimental Results ................................... 83
5.3.1. Deposition Efficiency ........................... 84
5.3.2. The Effect of the Particle Mass Flow Rate ....... 86
5.3.3. The Build-up Parameter .......................... 87
5.3.4. Structure and Properties ........................ 88
5.4. Basic Mechanisms ....................................... 91
5.5. Concluding Remarks ..................................... 94
6. Diagnostics of Spray Parameters: Characterization of the
Powder-Laden Jet ............................................ 95
6.1. General Relationships .................................. 95
6.1.1. The Governing Equations of Single-Phase
Turbulent Flow .................................. 97
6.1.2. The k-e Model for Turbulent Flows ............... 98
6.1.3. Particle Dynamics in Gas Flow ................... 98
6.2. Gas Flow and Particle Acceleration .................... 100
6.2.1. Computational Fluid Dynamics (CFD) ............. 102
6.2.2. An Engineering Model with Particle Friction .... 105
6.3. Calculated Data and Discussion ........................ 108
6.3.1. Simulation of Gas-Particle Flow in the
Nozzle ......................................... 108
6.3.2. Influence of Gas Pressure ...................... 111
6.3.3. Effects of Particle Concentration .............. 112
6.3.4. Effects of Nozzle Wall Friction ................ 114
6.4. Free Jet Characterization ............................. 116
6.4.1. Shock Wave Features of the Jet ................. 116
6.4.2. An Engineering Model of the Free Jet ........... 119
6.4.3. Particle Flow Structure Within the Normal
Shock Region ................................... 121
6.5. Concluding Remarks .................................... 124
7. Deposition Efficiency and Shock Wave Effects at GDS ........ 125
7.1. Model Structure ....................................... 125
7.1.1. Statement of Task .............................. 125
7.1.2. Gas Flow ....................................... 125
7.1.3. Particle Motion ................................ 127
7.1 4. Deposition Efficiency .......................... 127
7.2. Calculations and Discussion ........................... 128
7.3. Critical Velocity Evaluation on the Basis of
Rebound and Adhesion Phenomena ........................ 131
7.4. Concluding Remarks .................................... 132
8. Structure and Properties of GDS Sprayed Coatings ........... 135
8.1. General Remarks ....................................... 135
8.2. Powder Materials for Low-Pressure Gas Dynamic Spray ... 136
8.2.1. Features of GDS Coatings ....................... 136
8.2.1.1. Microstructure ........................ 136
8.2.1.2. Interparticle Bonding ................. 136
8.2.2. Overview of GDS Materials ...................... 138
8.2.3. Definition of Structure Parameters ............. 140
8.3. Structure and Mechanical Properties of Composite
Coatings .............................................. 142
8.3.1. Methods of Testing ............................. 142
8.3.1.1. Strength Tests ........................ 142
8.3.1.2. Determining the Elastic Modulus ....... 144
8.3.1.3. Preparation of Samples ................ 144
8.3.2. Analysis of the Elastic Modulus ................ 147
8.3.2.1. General Relationships ................. 147
8.3.2.2. Rule of Mixture (ROM) Bounds .......... 247
8.3.2.3. Hashin-Shtrikman (H-S) Model .......... 148
8.3.2.4. Effect of Porosity on Elastic
Constants ............................. 148
8.3.2.5. Development of MCA Model for GDS
Process ............................... 150
8.3.2.6. Elastic Modulus and Microstructure
of LPGDS Composites ................... 253
8.3.3. Load-Deformation Behavior of GDS Composites .... 258
8.3.3.1. Strengthening GDS composites .......... 158
8.3.4. Failure Criterion and Microstructural Aspects
of Crack Propagation ........................... 265
8.3.4.1. Analysis of LPGDS Composite
Fracture Characteristics .............. 266
8.4. Effect of Substrate Properties and Surface on the
Deposition Process .................................... 272
8.4.1. General Analysis and Effects of Residual
Stresses ....................................... 272
8.4.2. Microstructure Analysis of Interface ........... 273
9. Low-Pressure GDS Applications .............................. 181
9.1. General Analysis ...................................... 282
9.2. Repair Applications of GDS Technology ................. 285
9.2.1. LPGDS Composite Coatings for Mechanical
Components ..................................... 286
9.2.2. LPGDS Technology Characterization and
Experimental Procedure ......................... 287
9.2.3. Results and Discussion ......................... 289
9.2.3.1. Characterization ...................... 289
9.2.3.2. Sliding Wear Behavior ................. 289
9.2.3.3. Analysis of Worn Surfaces ............. 292
9.2.3.4. Wear Microstructure ................... 294
9.2.3.5. Wear Process .......................... 294
9.2.4. Casting Repair ................................. 295
9.2.5. Casting Die Components Repair .................. 296
9.2.6. Car Body Shape Repair .......................... 298
9.3. Hardening by LPGDS Deposition ......................... 298
9.3.1. General Remarks ................................ 298
9.3.2. LPGDS of Ni-SiC Powder Mixtures ................ 200
9.3.2.1. Deposition Efficiency ................. 200
9.3.2.2. Microhardness and Microscratching ..... 202
9.4. Corrosion Protection Through GDS Deposition ........... 206
9.4.1. General Remarks ................................ 206
9.4.2. Examination of Al-Zn-based Sacrificial
Coatings ....................................... 207
9.5. GDS Processing of Smart Components .................... 220
9.5.1. General Remarks ................................ 220
9.5.2. Technology Description ......................... 222
9.5.3. Results and Discussion ......................... 224
9.6. Concluding Remarks .................................... 117
Bibliography .................................................. 119
Index ......................................................... 231
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