Metallic Powders for Additive Manufacturing

Enrique J. Lavernia, PhD, is Professor and holder of the M. Katherine Banks Chair, Department of Materials Science and Engineering and Department of Mechanical Engineering, Texas A&M University, College Station. Kaka Ma, PhD, is Associate Professor in the Department of Mechanical Engineering and School of Materials Science and Engineering at Colorado State University, Fort Collins. Julie M. Schoenung, PhD, is Professor and holder of the Wofford Cain Chair III, Department of Materials Science and Engineering and Department of Mechanical Engineering, Texas A&M University, College Station. James F. Shackelford, PhD, is Distinguished Professor Emeritus in the Department of Materials Science and Engineering at the University of California, Davis. Baolong Zheng, PhD, is Project Scientist in the Department of Materials Science and Engineering at the University of California, Irvine.

• About the Authors xvPreface xixAcknowlegments xxiiiPart I Atomization of Metallic Powder 11 Overview of Atomization Techniques 31.1 History of Metallic Powder and Atomization Techniques 31.1.1 Metal Powders 31.1.2 Atomizer Designs 41.2 Melt Atomization 81.3 Gas Atomization (GA) 91.4 Vacuum Induction Gas Atomization (VIGA) 111.5 Electrode Induction Melting Gas Atomization (EIMGA) 121.6 Plasma Rotating Electrode Process (PREP) 151.7 Spark Plasma Discharge Spheroidization (SPDS) 161.8 Plasma Induction Gas Atomization (PIGA) 181.9 Plasma-Atomized Wire (PAW) 191.10 Water Atomization (WA) 201.11 Summary 22Nomenclature 23References 232 Atomization 252.1 Introduction 252.2 Atomization Technology 262.2.1 Energy Consumption During Atomization 262.2.2 Molten Metal Atomization Methods 272.2.3 Subsonic Gas Atomization 282.2.4 Supersonic Gas Atomization 302.2.5 Ultrasonic Gas Atomization (USGA) 312.2.6 Centrifugal Atomization 342.2.7 Mono-sized Droplet Atomization 362.3 Formation of Droplets 382.3.1 Regimes of Liquid Breakup 382.3.2 Mechanisms of Atomization 382.3.3 Atomization of Cylindrical Liquids 432.3.4 Atomization of Liquid Sheets 452.3.5 Droplet Formation Under Conventional Gas Atomization Conditions 472.3.6 Droplet Formation During Centrifugal Atomization 492.4 Control of Atomization Parameters 502.4.1 Classification of Processing Variables 502.4.2 Factors Affecting Metal Flow Rate 502.4.3 Metal Flow Rate 552.4.4 Gas Flow Rate and Velocity 572.5 Powder Size Distribution 612.5.1 Powder Size 622.5.2 Size Distribution 632.6 Effect of Processing Variables 642.6.1 Important Atomization Variables 642.6.2 Atomization Pressure 642.6.3 Liquid Flow Rate 662.6.4 Gas Velocity 672.6.5 Gas Flow Rate 692.6.6 Mechanical Disturbances 702.6.7 Physical Properties of Atomization Gas 712.6.8 Liquid Viscosity 712.6.9 Liquid Surface Tension 732.6.10 Fluid Temperature 742.6.11 Solidification Event 762.6.12 Apex Angle 782.6.13 Variables in Centrifugal Atomization 782.7 Theoretical Models of Atomization 802.7.1 Breakup of Liquid Rods or Fragments 802.7.2 Formation of Droplets by Sheet Breakup 822.8 Empirical Models 862.8.1 Nukiyama and Tanasawa Analysis 872.8.2 Wigg Analysis 872.8.3 Kim and Marshall Analysis 902.8.4 Schmitt Analysis 912.8.5 Weiss and Worsham Analysis 912.8.6 Lubanska Analysis 922.9 Summary 94Nomenclature 94References 963 Heat Transfer and Solidification of Droplets 1013.1 Introduction 1013.2 Important Thermal and Solidification Conditions 1033.2.1 Thermal Conditions 1033.2.2 Solidification Considerations 1053.3 Heat Transfer 1073.3.1 Heat Transfer Mechanisms 1073.3.2 Heat Transfer Coefficient 1093.3.3 Gas Velocity 1113.3.4 Droplet Velocity 1123.4 Nucleation 1163.4.1 Homogeneous Nucleation 1173.4.1.1 Free Energy of Nucleation 1173.4.1.2 Nucleation Rate 1203.4.1.3 Homogeneous Undercooling 1213.4.2 Heterogeneous Nucleation 1253.4.2.1 Heterogeneous Nucleants 1263.4.2.2 Heterogeneous Nucleation Undercooling 1283.4.2.3 Distribution of Nucleants 1303.5 Solidification of Droplets 1343.5.1 Temperature Distribution in Droplets 1353.5.2 Newtonian Solidification 1363.5.3 Cooling Rate 1373.5.4 Solidification Time 1403.5.5 Interfacial Velocity 1413.5.5.1 Equilibrium Solidification 1413.5.5.2 Dynamic Solidification 1433.5.5.3 Stepwise Growth 1453.5.5.4 Experimentally Determined Interfacial Velocities 1473.6 Microstructural Development 1513.6.1 Solidification Morphology 1513.6.2 Microstrutural Refinement 1553.6.2.1 Dendrite Arm Spacing 1553.6.2.2 Grain Size 1593.6.3 Phase Selection 1623.6.4 Solute Redistribution 1663.7 Summary 169Nomenclature 170References 1724 Composite Powders for Additive Manufacturing 1794.1 Introduction 1794.2 Fabrication Methods 1804.2.1 Atomization and Co-injection 1804.2.2 Atomization of Premixed MMCs 1864.2.3 Reactive Atomization 1864.2.3.1 Gas–Liquid Interactions 1864.2.3.2 Liquid–Liquid Interactions 1924.2.3.3 Liquid–Solid Interactions 1924.3 Incorporation of Reinforcements During Co-injection 1934.3.1 Incorporation Behavior of Reinforcements 1934.3.2 Penetration of Semiliquid Droplets 1974.3.2.1 Energy Balance 1984.3.2.2 Force Balance 2004.3.2.3 Combined Energy and Force Balance 2014.3.2.4 Penetration Depth 2044.3.2.5 Particle Type, Morphology, and Solid Fraction 2044.3.3 Penetration of Solid Droplets 2064.4 Particle Behavior During Solidification 2074.4.1 Engulfment of Reinforcements by Solid–Liquid Interface 2074.4.1.1 Mass Balance 2094.4.1.2 Force Balance 2094.4.1.3 Thermal Field 2104.4.1.4 Thermal Field and Force Balance 2114.4.1.5 Engulfment During Droplet Solidification 2114.4.2 Mechanical Entrapment of Reinforcements by Solidification Fronts 2134.4.3 Reinforcement-Induced Nucleation 2144.4.3.1 Free Energy Effects 2144.4.3.2 Thermal Effects 2154.5 Other Methods for Fabricating MMC Powders 2194.5.1 Mechanical Milling and Cryomilling 2204.5.2 Surface Coating 2244.5.3 Reaction Synthesis 2264.6 Summary 227Nomenclature 228References 2305 Diagnostic and Characterization Techniques 2355.1 Introduction 2355.2 Flow Visualization Techniques 2355.3 Particle Image Velocimetry (PIV) 2395.4 Particle Counting, Sizing, and Velocity Probe (PCSV-P) 2435.5 High-Speed Cinematography/Video 2465.6 High-Speed Off-Axis Holographic Cinematography 2495.7 Infrared Thermal Imaging 2525.8 Phase Doppler Particle Analysis (PDPA) 2535.9 Surface Ionization For Monitoring Particles (SIMP) 2555.10 Intelligent Sensors 2555.11 Summary 259References 2606 Atomization Improvements for Additive Manufacturing 2636.1 Introduction 2636.2 Gas and Metal Flow Rates 2636.3 Gas Velocity 2646.4 Physical Characteristics of the Gas and Melt 2656.5 Powder Size Distribution and Other Variables 2666.6 Powder Morphology 2686.7 Powder Satellites 2726.8 Powder Porosity 2756.9 Summary 278Nomenclature 278References 2797 Atomization of Alloys 2837.1 Introduction 2837.2 Aluminum-Based Alloys and Powders 2837.2.1 Al-Based Alloy Powders 2847.2.2 Al–Si Alloys 2857.2.3 Al–Cu Alloys 2887.2.4 Al–Transition Metal Alloys 2897.2.5 Al–Li Alloys 2897.2.6 Al–Zn–Mg–Cu Alloys 2927.3 Iron-Based Alloys and Powders 2967.3.1 Fe-Based Alloy Powders 2977.3.2 Stainless Steels 3007.3.3 Tool Steels 3017.3.4 Other Iron-Based Materials 3037.4 Nickel-Based Alloys and Powders 3037.4.1 Ni-Based Alloy Powders 3047.4.2 Inconel Alloys 3067.4.3 René Alloys 3087.4.4 Other Superalloys 3107.5 Titanium-Based Alloy and Powders 3117.5.1 Ti-Based Alloys 3117.5.2 Ti-Based Alloy Powders 3137.6 Cobalt-Based Alloys and Powder 3197.6.1 Co-Based Alloys 3197.6.2 Co-Based Alloy Powders 3217.7 High-Entropy Alloys and Powders 3237.7.1 High-Entropy Alloys 3237.7.2 High-Entropy Alloy Powders 3257.8 Summary 329Nomenclature 329References 331Part II Powders in Additive Manufacturing 3418 Overview of Metal Additive Manufacturing Technologies 3438.1 History of Metal Additive Manufacturing Techniques 3438.2 Powder Bed Fusion (PBF) 3458.2.1 PBF Processing Principles 3458.2.2 Feedstock Powder for PBF 3478.2.3 Post-processing After PBF 3488.3 Directed Energy Deposition (DED) 3488.3.1 DED Processing Principles 3488.3.2 Feedstock Powder for DED 3498.3.3 Post-processing After DED 3518.4 Metal Binder Jetting 3518.4.1 BJT Processing Principles 3518.4.2 Feedstock Powder for BJT 3528.4.3 Post-processing After BJT 3528.5 Sheet Lamination (SHL) 3538.6 Summary 354Acronym/Nomenclature 354References 3559 Powder–Laser–Melt Pool Interactions 3619.1 Introduction 3619.2 Laser and Laser-Material Interactions 3629.2.1 Laser–Matter Interactions 3629.2.2 Laser-Material Processing 3639.3 Laser-Material Interactions During DED Processing 3649.3.1 Inflight Particle Heating 3649.3.2 Thermal Behavior of Melt Pool 3669.3.3 Interactions Between Particles and Melt Pool 3679.4 Laser-Material Interactions During PBF Processing 3729.4.1 Powder Layer Characteristics and Spreading 3739.4.2 Laser Beam–Powder Interactions 3759.4.3 Spatter and Denudation Formation 3789.4.4 Powder Degradation 3819.5 Summary 383Nomenclature 383References 38410 Influence of Powder Chemistry on Additive Manufacturing 38710.1 Introduction 38710.2 Alloy Compositions 38710.3 Impurities and Segregation 39110.4 High Entropy Alloys (Multi-Principal Element Alloys) 39210.5 Metal Matrix Composites 39410.6 In-Situ Alloying (In-Process Alloying) 39610.7 Summary 397Nomenclature 397References 39711 Physical Powder Characteristics and Additive Manufacturing 40311.1 Introduction 40311.2 Characterization of Physical Powder Properties 40311.2.1 Powder Sampling 40311.2.2 Particle Size and Particle Size Distribution 40511.2.3 Particle Morphology 40711.2.4 Powder Flow Characteristics 40911.3 Powder Production Methods 41211.3.1 Gas Atomization 41311.3.2 Water Atomization 41311.3.3 Mechanical Milling 41411.4 Powder Reuse, Recycling, and Recovery 41411.5 Influence of Powder Production Methods and Parameters On Powder Properties and Additive Manufacturing 41611.6 Influence of Powder Reuse, Recycling, and Recovery on Powder Characteristics and Additive Manufacturing 42011.7 Postproduction Methods for Treating Powders 42311.8 Summary 425Nomenclature 426References 42712 Microstructure Evolution and Powder Effects 43312.1 Introduction 43312.2 Grain Structure and Phase Composition 43312.2.1 Columnar-to-Equiaxed Transition (CET) 43312.2.2 Phase Composition 43912.3 Solidification Kinetics 44112.4 Solid-State AM 44512.5 Summary 448Nomenclature 448References 45013 Defect Formation and Powder Effects 45513.1 Introduction 45513.2 Porosity 45513.3 Cracking and Delamination 46013.4 Interfacial Structure and Grain Size 46213.5 Segregation 47013.6 Surface Roughness 47213.7 Summary 475Nomenclature 475References 47614 Residual Stress and Powder Effects 47914.1 Introduction 47914.2 Measuring Residual Stress 47914.3 Powder Characteristics 48114.4 Pre-processing Heat Treatment 48214.5 Process Parameters 48314.6 Post-processing Treatments 48714.7 Summary 490Nomenclature 490References 49115 Physical and Chemical Behavior and Powder Effects 49315.1 Introduction 49315.2 Density 49315.3 Surface Appearance 49415.4 Elastic and Plastic Deformation 49615.5 Hardness 49715.6 Fracture and Fatigue 49815.7 Corrosion and Wear 50215.8 Oxidation 50915.9 Summary 510Nomenclature 511References 51116 Economic and Sustainability Assessments of Powder Production and Additive Manufacturing 51316.1 Introduction 51316.2 Resource Utilization 51316.2.1 Materials Utilization 51416.2.2 Energy Utilization 51616.2.3 Other Resources 51816.3 Economic Assessment 51916.3.1 Cost Breakdown and Models 52016.3.2 Supply Chain Effects 52416.4 Sustainability Assessments 52716.4.1 Hazard Traits of Metals and Occupational Exposure Potential 52816.4.2 Life Cycle Assessment of Environmental Impact 54216.5 Summary 546Nomenclature 547References 54917 Future Directions and Challenges 55517.1 Introduction 55517.2 Future Directions in the Atomization of Powders 55617.2.1 Technology Improvements 55617.2.2 Custom Alloys and Composites 55717.2.3 Additive Manufacturing 55717.3 Future Directions and Challenges in the Additive Manufacturing of Metal Alloys 55817.3.1 Machine Learning and Artificial Intelligence 55817.3.2 Novel Structures 56017.3.3 Hybrid Manufacturing 56017.3.4 Diagnostic Methods 56117.3.5 Future Challenges 56117.4 Summary 561References 562Index 565