| | Contents | |
| | | |
| |
| | Preface | XI |
| 1 | Introduction | 1 |
| 1.1 | General Description | 1 |
| 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 | 10 |
| 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— 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 |
| 6.4.4 | Particle Collisions | 123 |
| 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 | 147 |
| 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 | 153 |
| 8.3.3 | Load-Deformation Behavior of GDS Composites | 158 |
| 8.3.3.1 | Strengthening GDS composites | 158 |
| 8.3.4 | Failure Criterion and Microstructural Aspects of Crack Propagation | 165 |
| 8.3.4.1 | Analysis of LPGDS Composite Fracture Characteristics | 166 |
| 8.4 | Effect of Substrate Properties and Surface on the Deposition Process | 171 |
| 8.4.1 | General Analysis and Effects of Residual Stresses | 171 |
| 8.4.2 | Microstructure Analysis of Interface | 173 |
| 9 | Low-Pressure GDS Applications | 181 |
| 9.1 | General Analysis | 181 |
| 9.2 | Repair Applications of GDS Technology | 185 |
| 9.2.1 | LPGDS Composite Coatings for Mechanical Components | 186 |
| 9.2.2 | LPGDS Technology Characterization and Experimental Procedure | 187 |
| 9.2.3 | Results and Discussion | 189 |
| 9.2.3.1 | Characterization | 189 |
| 9.2.3.2 | Sliding Wear Behavior | 189 |
| 9.2.3.3 | Analysis of Worn Surfaces | 192 |
| 9.2.3.4 | Wear Microstructure | 194 |
| 9.2.3.5 | Wear Process | 194 |
| 9.2.4 | Casting Repair | 195 |
| 9.2.5 | Casting Die Components Repair | 196 |
| 9.2.6 | Car Body Shape Repair | 198 |
| 9.3 | Hardening by LPGDS Deposition | 198 |
| 9.3.1 | General Remarks | 198 |
| 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 | 210 |
| 9.5.1 | General Remarks | 210 |
| 9.5.2 | Technology Description | 211 |
| 9.5.3 | Results and Discussion | 214 |
| 9.6 | Concluding Remarks | 217 |
| | Bibliography | 219 |
