Metal Sprays and Spray Deposition (eBook)

Professor Hani Henein is at the Department of Chemical and Materials Engineering of the University of Alberta. Prof. Dr. Ing. Volker Uhlenwinkel and Prof. Dr. Ing. Udo Fritsching are at the Mechanical Engineering and Process Engineering Department of the University of Bremen.

Preface 5
Contents 6
Chapter 1: Introduction 8
References 13
Chapter 2: Single Fluid Atomization Fundamentals 15
2.1 Introduction 15
2.2 Droplet Formation 16
2.2.1 Mechanism of Stream Breakup 16
2.2.2 Boundary Between Stream and Dripping Formation 18
2.2.3 Stream Breakup Regimes 20
2.2.4 Spheroidization 21
2.3 Theoretical Energy Requirement 22
2.4 Single Fluid Atomization Techniques 23
2.4.1 Overview of Existing Techniques 23
2.4.2 Centrifugal Atomization 24
2.4.2.1 Melt Flow Disintegration 25
2.4.2.2 Droplet Generation and Parameters 27
2.4.2.3 Rotating Speed and Material Properties 28
2.4.2.4 Atomizer Size and Shape 28
2.4.2.5 Feed Rate, Wettability and Oxygen Content 30
2.4.2.6 Process Design 30
2.4.3 Drop on Demand Techniques (POEM, PDOD, StarJet) 31
2.4.3.1 Pulsated Orifice Ejection Method (POEM) 31
2.4.3.2 Pneumatic Drop-on-Demand Technique (PDOD) 32
2.4.3.3 StarJet Technology 34
2.4.4 Continuous Uniform Droplet Generation (UDG) Based on Rayleigh Instability 35
2.4.5 Impulse Atomization Process (IA) 36
2.4.5.1 Heat Transport 38
2.4.5.2 Cooling Rate 41
2.4.5.3 Microstructures 42
2.4.5.4 Quantification of Dendritic and Eutectic Nucleation Undercoolings 45
2.4.5.5 Estimation of Eutectic Fraction and Undercooling 46
2.4.5.6 Estimation of Primary Undercooling 48
2.5 Summary 50
2.6 List of Symbols 50
2.6.1 Latin 50
2.6.2 Greek 51
2.6.3 Indicies 51
References 52
Chapter 3: Two Fluid Atomization Fundamentals 55
3.1 Introduction 55
3.2 Gas Atomization Configurations 56
3.2.1 Free-Fall Gas Atomization (FFA) 56
3.2.1.1 Introduction 56
3.2.1.2 Dual Nozzle Improvement 57
3.2.1.3 Discussion 59
3.2.2 Close-Coupled Gas Atomization (CCGA) 60
3.2.2.1 Introduction 60
3.2.2.2 Discussion 62
3.2.2.3 Control of Primary Atomization in CCGA 63
Introduction 63
Results 67
Discussion 68
3.2.2.4 Pulsatile Shock-Enhanced Disintegration in CCGA 68
Introduction 68
Dual Manifold Nozzle Design 69
Nozzle Lab Testing 71
Summary 76
3.3 Hybrid Atomization 76
3.3.1 Introduction 76
3.3.2 Discussion 76
3.3.3 Pressure-Swirl Film Formation Plus Gas Jet Disintegration 77
3.3.3.1 Introduction 77
3.3.3.2 The Pressure-Swirl Filming/Gas Atomizer Concept 77
3.3.3.3 Initial Results 78
3.4 Isolated Effects of the Pressure-Swirl Nozzle 79
3.4.1 Isolated Effects of the Gas Flow Field 81
3.4.2 Effects of Gas Recirculation and Melt Properties 83
3.4.2.1 Improved Results 83
3.4.2.2 Discussion 84
3.5 Rotary Film Formation Plus Gas Jet Disintegration 86
3.5.1 Introduction 86
3.5.2 Rotary Filming/Gas Atomizer Concept 86
3.5.3 Numerical Simulation 87
3.5.4 Model Experiments 88
3.5.5 Viscous Melt Atomization Experiments 89
3.5.6 Overall Conclusions 90
3.6 List of Symbols 91
3.6.1 Latin 91
3.6.2 Greek 92
References 92
Chapter 4: Spray Transport Fundamentals 95
4.1 Introduction 95
4.2 Near-Field Gas Flow Dynamics 96
4.2.1 Close-Coupled Atomizer 97
4.2.2 Free-Fall Atomizer 101
4.3 Liquid Metal Jet Disintegration 105
4.3.1 Flow Regimes 106
4.3.1.1 Twin-Fluid Atomizer 106
4.3.2 Numerical Simulation of Liquid Jet Breakup 108
4.3.2.1 Direct Numerical Simulation 108
4.3.2.2 RANS Approach and LES 112
4.3.2.3 Multiscale Model 115
4.4 Secondary Atomization 118
4.4.1 Droplet Breakup Models 119
4.4.1.1 Semi-Empirical Models 119
4.4.1.2 Droplet-Deformation Based Models 121
4.4.1.3 Wave and KH-RT Hybrid Breakup Model 123
4.4.1.4 Empirical Extension of Droplet Deformation Model 125
4.5 Spray Behaviour 126
4.5.1 Drop Size Correlations in Sprays 127
4.5.1.1 Theoretical Analysis 127
4.5.1.2 Empirical Drop Size Correlations 128
4.5.2 Dense Spray 129
4.5.2.1 Droplet and Droplet Collisions 129
4.5.2.2 DNS of Droplet Collisions 131
4.5.2.3 Numerical Models of Droplet Collisions in Sprays 133
4.5.2.4 Clustering of Droplets 136
4.5.3 Dilute Spray 142
4.5.3.1 Droplet Movement 142
Momentum Transfer and Droplet Trajectory 142
Turbulent Dispersion of Particles in the Spray 145
4.5.3.2 Heat Transfer and Droplet Cooling 146
4.5.3.3 Droplet Transport in the Spray 148
4.5.3.4 Spray Cone Spreading 152
4.5.3.5 Spray/Environment Interaction, Entrainment 155
Recirculation Flow Rate 157
Reattachment Point 158
Shear Gradient 159
Spray Chamber Design 159
4.5.4 Three-Phase Spray Process for MMC Production 162
4.5.4.1 Particle-Droplet Mixing Behaviour 165
4.5.4.2 Particle-Droplet Collision Behaviour 166
4.5.4.3 Particle Penetration Behaviour 167
Force/Energy Balance Approach 167
CFD Simulation 168
4.5.4.4 Incorporation Efficiency and Sticking Efficiency 169
4.6 List of Symbols 170
4.6.1 Latin 170
4.6.2 Greek 171
References 172
Chapter 5: Spray Impingement Fundamentals 183
5.1 Introduction 183
5.2 Impact of Molten Metal Droplets on Surfaces 185
5.2.1 Photographing Droplet Impact 185
5.2.2 Droplet Impact Dynamics 188
5.2.3 Thermal Contact Resistance 189
5.2.4 Surface Roughness Effects 191
5.2.5 Droplet Splashing and Fragmentation 193
5.2.6 Splat Shapes 195
5.2.7 Residual Stresses and Splat Deformation During Solidification 197
5.3 Numerical Modeling of Droplet Impact 199
5.3.1 Governing Equations 199
5.3.2 Interface Tracking 199
5.3.3 Heat Transfer and Solidification 201
5.3.4 Initial and Boundary Conditions 202
5.3.5 Simulations of Droplet Impact 203
5.3.5.1 Effect of Solidification on Break-up 203
5.3.5.2 Effect of Surface Roughness on Impact Dynamics 204
5.3.5.3 Impact of Partially Molten Droplets 205
5.4 Spray Impingement 207
5.4.1 Coalescence of Droplets Impacting on a Surface 207
5.4.2 Spray Deposition 209
5.4.3 Porosity Formation 212
5.5 Modeling Spray Impingement 213
5.5.1 Monte-Carlo Simulations 213
5.5.2 Smoothed Particle Hydrodynamics 215
5.6 Summary 221
5.7 List of Symbols 221
5.7.1 Latin 221
5.7.2 Greek 222
References 223
Chapter 6: In-Situ, Real Time Diagnostics in the Spray Forming Process 227
6.1 Principles of In-situ Particle Diagnostics and Sensors 229
6.2 Melt Flowrate 230
6.3 Laser Based Techniques 232
6.3.1 PCSV-P 232
6.3.2 EPSV 233
6.3.3 Light Scattering Sensing: Phase-Doppler-Anemometry 234
6.4 Optical Based Techniques 242
6.5 Pyrometery 244
6.5.1 Description of the DPV Pyrometer Spray Monitoring System 244
6.5.1.1 The Sensing Head 245
6.5.1.2 The Detection Cabinet 245
6.5.2 Signal Processing and Calculation of the Parameters 246
6.5.2.1 Velocity 247
6.5.2.2 Temperature 247
6.5.2.3 Diameter 248
6.5.3 DPV Application to Gas Atomized Metal Sprays 248
6.5.4 DPV-2000 Hypotheses 254
6.5.5 DPV-2000 Diameter Measurement 254
6.5.6 DPV in Single Fluid Atomization and Powder Characterization 256
6.5.6.1 Velocity, Size and Radiant Energy Measurements 258
6.5.6.2 Droplet Temperature Calculations 260
6.5.6.3 Validity of Two Color Pyrometry Assumption 261
6.5.6.4 Droplet Size and Temperature Estimation at the Solidification Point 263
6.5.6.5 Precision of In-situ, Real Time Diagnostics 265
6.6 Summary 265
6.7 List of symbols 266
6.7.1 Latin 266
6.7.2 Greek 266
References 267
Chapter 7: Microstructural Evolution in Spray Forming 270
7.1 Introduction 270
7.2 Spray Forming as a Bulk Process 271
7.3 The Evolution of the Spray Formed Grain Size and Shape-Thermal Conditions 273
7.4 The Evolution of the Spray Formed Grain Size and Shape: Polygonal Grains 275
7.5 The Evolution of the Spray Formed Grain Size and Shape: Micro and Macro-Segregation 277
7.6 Layering/Non-Layering 279
7.7 Porosity 281
7.8 Residual Stress and Hot Cracks 288
7.9 Effect of Atomization Gas Nitrogen and Argon 295
7.9.1 Steels 295
7.9.2 Superalloys 297
7.9.3 Copper Alloys 298
7.10 List of Symbols 298
7.10.1 Latin 298
7.10.2 Greek 298
References 298
Chapter 8: Processing Aspects in Spray Forming 301
8.1 Process Description 301
8.1.1 Single Fluid Atomization 301
8.1.1.1 Impulse Atomization 302
8.1.1.2 Centrifugal Spray Deposition (CSD) 302
8.1.1.3 Uniform Droplet Spray Forming 304
8.1.2 Gas Atomization 306
8.1.3 Metal Matrix Composite 309
8.1.4 Co-Spray Forming 311
8.2 Spray Cone 316
8.2.1 Mass Flux Distribution 316
8.2.1.1 Measuring of Local Mass Flux in a Molten Metal Spray 316
8.2.1.2 Free-Fall-Atomizer 317
8.2.1.3 Empirical Correlation 319
8.2.2 Heat Transfer and Enthalpy Distribution 320
8.2.2.1 Caloric Probes 320
8.2.2.2 Distribution of Specific Enthalpy in the Spray Cone 321
8.3 Deposition 324
8.3.1 Overspray, Yield, and Sticking Efficiency 324
8.3.2 Deposit Temperature and Cooling Rate (or Thermal Evolution of Deposit) 329
8.4 Microstructure Evolution 338
8.5 List of Symbols 348
References 349
Chapter 9: Characterization of as-Spray-Formed Products 353
9.1 Introduction 353
9.2 Porosity 354
9.2.1 Relative Density and Porosity Distribution 354
9.2.2 Porosity Morphology 361
9.3 Material Homogeneity and Cleanliness 362
9.3.1 Macrosegregation 362
9.3.2 Microsegregation 362
9.3.3 Cleanliness 363
9.4 Microstructure 364
9.4.1 Grain Structure and Morphology 364
9.4.2 Grain Size and Distribution 365
9.4.3 Phase Structure and Morphology 367
9.4.4 Phase Size, Shape and Distribution 370
9.4.5 Phase Transformation 371
9.4.6 Extension of Solid Solubility 373
9.4.7 Nitrogen Pick-Up 374
9.5 Deformation Behavior 374
9.6 Residual Stresses and Strains 375
9.7 List of Symbols 379
References 379
Chapter 10: Spray Forming of Aluminium Alloys 383
10.1 Introduction 383
10.2 Post Processing 383
10.3 Premium Products 387
10.4 Near-to-Net Shape Manufacture 389
10.5 Better Properties 392
10.5.1 Young´s Modulus 393
10.5.2 Thermal Expansion 393
10.5.3 High Strength 393
10.5.4 Low Density 394
10.5.5 Hot Strength 395
10.5.6 Fatigue 398
10.5.7 Wear Resistance 399
10.6 Impossible Alloys 401
10.7 Conclusion and Outlook 403
References 404
Chapter 11: Spray Forming of Copper Alloys 411
11.1 Introduction 411
11.2 Spray Forming Plant for Production of Copper Alloy Billets 412
11.2.1 Classification of the Process 412
11.2.2 Process Description 412
11.2.3 Differences from Conventional Casting Processes 415
11.3 Materials Groups 416
11.3.1 High Alloyed Copper Materials 416
11.3.1.1 Tin Bronze 416
Homogeneous Element Distribution in Spray-Formed Bronze 416
Homogeneous Microstructure of Spray-Formed Bronze 417
Grain Structure 417
Intermetallics Structure 418
Microstructure Development During Production Process 420
11.3.1.2 Cu-Mn-Ni 420
11.3.1.3 Aluminium Bronze 423
Experimental Procedure and Investigated Materials 423
Results 425
Microstructure Investigation 425
Mechanical and Physical Properties 427
Properties at Elevated Temperatures 428
Overlay Welding 430
Machinability 431
11.3.1.4 Copper-Nickel-Silicon Alloys 431
11.3.2 MMC 435
11.3.2.1 Injection of a Second Component 435
11.3.2.2 Reactive Spray Forming 436
11.4 Applications 438
11.4.1 Low Temperature Superconductor (CuSn) 438
11.4.1.1 Requirements to High-Tin-Bronze Semi-Finished Material 440
11.4.1.2 Advantages of Spray-Formed High-Tin-Bronze 440
11.4.2 Oil Drilling Equipment (Cu-20Mn-20Ni) 441
11.4.3 Cold Working Tools and Injection Moulds (Al-Bronze) 441
11.5 Quality 443
11.5.1 Segregation 443
11.5.2 Porosity 448
11.5.2.1 Definition and Measurement of Porosity 448
11.5.2.2 Reactive Elements Influencing Porosity 450
11.5.2.3 The Effect of Titanium on Porosity 451
11.5.3 Detection of Pores and Cracks 454
11.5.3.1 Porosity Measurement 454
11.5.3.2 Ultrasonic Test 457
Preliminary Tests 457
Ultrasonic Test Setup 459
Standard Test Routine 461
11.6 Summary and Outlook 461
11.7 List of Symbols 463
References 464
Chapter 12: Spray Forming of Steels 467
12.1 Introduction 467
12.2 Processing of Steels by Spray Forming 468
12.2.1 Comparison to Other Manufacturing Routes 468
12.2.2 Spray Forming of Steel Preforms 470
12.2.2.1 Round Billets 470
12.2.2.2 Mill Rolls and Tubes 472
12.2.2.3 Molds and Dies 475
12.3 Spray Formed Steels and Iron Based Alloys 477
12.3.1 Tool Steels 478
12.3.1.1 High-Speed Steels 478
12.3.1.2 Cold-Work Tool Steels 481
12.3.1.3 Hot-Work Tool Steels 483
12.3.2 Low-Alloy Steels 485
12.3.2.1 Low- and Medium-Carbon Steels 485
12.3.2.2 High-Carbon Steels 486
12.3.2.3 Ultrahigh Carbon Steels 487
12.3.3 Stainless Steels 488
12.3.4 High-Chromium White Cast Irons 490
12.3.5 Steel Matrix Composites 491
12.4 Summary 492
References 493
Chapter 13: Spray Forming of Nickel Superalloys 500
13.1 Introduction 500
13.2 Microstructure of Ni-Based Superalloys 501
13.2.1 Cast and Wrought Processing of Superalloys 504
13.2.2 Powder Metallurgy Processing of Superalloys 505
13.2.3 Spray Forming of Superalloys 506
13.3 History of Superalloy Spray Forming 507
13.4 Spray Forming of Superalloy Rings 510
13.5 Spray Forming of ESR Liquid Metal 513
13.6 Electric Arc Spray 517
13.7 Summary and Outlook 518
Trademark Identification 519
CRS Holdings: A Subsidiary of Carpenter Technology Corporation 519
General Electric Corporation 519
Haynes Alloys International 519
Howmet Corporation 519
Martin Metals Corporation 519
Special Metals Corporation: A Wholly Owned Subsidiary of Precision Castparts Corp. 519
United Technologies Corporation 519
References 520
Chapter 14: Spray Forming of Novel Materials 524
14.1 Introduction 524
14.2 Essence of Amorphous Metallic Alloys 526
14.3 Fundamentals of Bulk Metallic Glasses 529
14.3.1 Glassy Alloys 529
14.3.2 Criteria for Glass Forming Ability 532
14.3.2.1 Main Systems and Existing Alloys 536
14.4 Spray Forming Process 538
14.5 Investigations on Spray Forming of Glass Forming Alloys 541
14.5.1 Aluminum Based Alloys 542
14.5.2 Iron Based Alloys 546
14.5.3 Other Alloys 550
14.6 Mechanisms of Microstructural Evolution 551
14.6.1 Process Control for Amorphous/Nanocrystalline Materials 551
14.6.1.1 Atomization and Droplets in Flight 551
14.6.1.2 Droplets on Deposition 551
14.6.1.3 Deposit Cooling 552
14.6.2 Microstructure Constitution of the Spray 553
14.6.3 The Transient Layer on Deposition 556
14.7 Perspectives on Future Developments 558
14.8 List of Symbols 560
References 560
Index 565