Practical Cold Spray

This book provides a detailed explanation of the cold spray process from a practical standpoint. Drawing on the authors’ 36 years of research and development experience, it is firmly rooted in theory but also substantiated by empirical data and practical knowledge, offering potential users the information they need to recognize the advantages, as well as the limitations, of cold spray. This sets it apart from previous works on the subject, which have been purely academic. Cold spray technology has made great dramatic strides over the last 10 years and is now being used extensively in the aerospace, electronics, automotive, medical, and even the petrochemical industries. Most recently, cold spray of near-net shaped parts was accomplished – something previously assumed to be impossible because of the limitations of commercially available cold spray systems and a lack of fundamental understanding regarding the process. The cost of cold spray has also declined, making it appealing to industry through the introduction of new powders, surface preparation techniques, and recovery systems tailored to the cold spray process. Though primarily intended for users of the technology, this handbook is also a valuable resource for researchers interested in advances in cold spray materials, improved feedstock powders, advanced hardware and software development, surface preparation techniques, and the numerous applications developed to date. For example, cold spray aluminum alloys have been developed that offer the strength and ductility of wrought material in the as-sprayed condition. This has yet to be achieved by conventional powder consolidation methods including laser sintering, electron beam, and ultrasonic techniques. Other topics covered include additive manufacturing, structural repair, nondestructive evaluation, advanced cold spray materials, qualification requirements, cold spray systems comparison, and, finally, helium recovery. Thanks to its practical focus, the book provides readers with everything they need to understand, evaluate, and implement cold spray technology. Preface Contents 1 Introduction 1.1 Process Description 1.2 Comparison to Thermal Spray 1.3 Advantages and Limitations 1.3.1 Strength 1.3.2 Hardness 1.3.3 Variety of Feedstock Powders 1.3.4 Cost 1.3.5 Ease of Production and Portability 1.3.6 Additive Manufacturing 1.4 Summary of Advantages and Limitations 1.4.1 Advantages 1.4.2 Limitations References 2 Process Description 2.1 Introduction 2.2 Cold Spray Process 2.3 System Classification 2.3.1 Classifying Cold Spray Systems According to the Mode of Operation 2.3.2 Classifying Cold Spray Systems According to Powder Feeding and Acceleration Mechanism 2.4 Supersonic and Sonic Nozzle Description 2.5 Cold Spray Powders 2.6 The Deposition Process 2.7 Powder and Substrate Hardness 2.8 Deposition Efficiency 2.9 Deposition Path 2.10 Nozzle Materials 2.11 Fundamentals of Cold Spray Process 2.11.1 Gas Flow in Cold Spray 2.12 Particle Flow Behavior 2.12.1 Particle Velocity 2.12.2 Particle Heat Transfer 2.13 Bonding Mechanism References 3 Setting Up a Cold Spray Facility 3.1 Introduction 3.2 Cold Spray Unit 3.3 Gas Supply 3.3.1 Nitrogen 3.3.2 Helium 3.4 Powder and Gas Control 3.5 Ventilation and Dust Control 3.6 Acoustic Enclosure 3.7 Robotic Motion Control 3.8 Equipment Placement 3.9 Safety 3.9.1 Environmental Safety 3.9.2 Solid Powders 3.9.3 Inert Gases 3.9.4 High Pressure Gases 3.9.5 Hearing Hazards 3.9.6 Hot Surfaces 3.9.7 Flying Objects 3.9.8 Robot Safety 3.9.9 Maintenance of Safety Systems and PPE 3.9.10 Fire/Explosion Safety 3.10 Auxiliary Equipment 3.11 Summary of Equipment References 4 Feedstock Powders 4.1 Significance of Powder Microstructure in Cold Spray 4.2 Correlation Between Powder and Deposit Microstructures 4.2.1 Microstructural Phases in Powders and Deposits 4.2.2 Grain Size in Powder and Deposits 4.2.3 Relationship of Deformation with Inter-Particle Bonding 4.3 Introduction to Powder Basics 4.3.1 Size Distribution 4.3.2 Powder Flowability 4.3.3 Morphology 4.3.4 Hardness 4.3.5 Adsorbed Moisture (Flow and Degas During AM) 4.4 Desirable Powder Characteristics 4.4.1 Surface (Oxides, Hydroxides) 4.4.2 Interior (Homogenization, Phase Transformations) 4.5 Processing Required to Achieve Desirable Powder 4.5.1 Heat Treatment 4.5.2 Size Classification 4.6 Multi-phase Powders 4.7 Concluding Remarks References 5 Material Properties 5.1 Aluminum 5.1.1 Aluminum Properties 5.2 Brass and Bronze 5.3 Copper 5.3.1 Copper Properties 5.3.2 Alloys of Copper 5.3.3 Cold Spray Copper 5.4 Titanium 5.4.1 Titanium 5.4.2 Uses 5.4.3 Cold Spray Titanium 5.5 Stainless Steel 5.5.1 Stainless Steel Uses 5.5.2 Cold Spray Stainless Steel 5.6 Nickel 5.6.1 Nickel Properties and Common Use 5.6.2 Cold Spray Nickel 5.7 Tantalum 5.7.1 Tantalum Properties and Common Use 5.7.2 Cold Spray of Tantalum 5.8 Alloys for Replacing Chrome and Nickle Electroplating 5.8.1 Electroplated Cr and Ni Replacement Powders 5.9 Inconel 5.10 Polymers and Composites References 6 Application, Qualification, and Standardization of Cold Spray 6.1 Introduction 6.2 Identification of Applicable Standards, Governing Bodies, and Approval Authorities 6.3 Standards and Guidelines Applicable to Cold Spray 6.3.1 Powder Specification Standards 6.3.2 Applicable Cold Spray Standards 6.3.3 Applicable Thermal Spray Standards 6.4 Writing New Standards 6.4.1 Having a Controlled and Bounded Process 6.4.2 Acceptable Versus Unacceptable Variation 6.4.3 Evaluating Process Variation Versus Property Variation 6.4.4 Testing 6.4.5 Obtaining Stakeholder Involvement 6.4.6 Funding the Qualification Effort 6.5 Quality Testing 6.5.1 Impact Testing 6.5.2 Microscopic Examination 6.5.3 Adhesion Tensile Bond Strength 6.5.4 ARL ‘Glueless’ Bond Strength Test 6.5.5 Triple Lug Shear Adhesion 6.5.6 Tensile Testing 6.5.7 Fretting Fatigue 6.5.8 Corrosion Testing 6.6 Nondestructive Evaluation of Cold Spray Deposited Products 6.6.1 Ultrasonic Testing 6.6.2 Acoustic Emissions Testing 6.6.3 Eddy Current Testing 6.6.4 Dye Penetrant Testing 6.6.5 Magnetic Particle Testing 6.6.6 Radioscopy 6.6.7 Visual-Optical 6.7 Troubleshooting 6.7.1 Cold Spray Process Related Problems 6.7.2 Leaks, Clogs, and Nozzle Wear 6.7.3 Component Failures 6.8 Example of Cold Spray Procedure Qualification 6.8.1 Project Structure 6.8.2 Development of a Joint Test Protocol (JTP) 6.9 Summary References 7 Process Control 7.1 Introduction 7.2 Surface Preparation 7.3 Basic Parameters 7.3.1 Gas Conditions 7.3.2 Particle Velocity and Temperature Determination 7.3.3 The Critical Velocity 7.3.4 Gas and Powder Flow Rates 7.4 Application Setup 7.5 In Situ Process Analysis 7.5.1 In Situ Particle Velocity Measurement 7.5.2 In Situ Coating Property Sensing 7.6 Summary References 8 Cold Spray Economics 8.1 Introduction 8.2 Basic Framework 8.3 Powders 8.4 Gas 8.5 Powder Mass Loading 8.6 Direct Labor Costs 8.7 Overhead 8.8 Depreciation and Capital Recovery 8.9 Examples of Cost Calculations 8.10 Effects of Process Variables 8.10.1 Gas 8.10.2 Powder Feed 8.10.3 Powder Cost 8.10.4 Deposition Efficiency 8.10.5 Utilization 8.10.6 Number of Pieces to Be Produced 8.11 Determination of Operating Parameters 8.12 Production Capacity 8.13 Important Factors in Determining the Viability of a Cold Spray Repair 8.14 Concluding Thoughts References 9 Advancements in Cold Spray 9.1 Introduction 9.2 Intelligent Process Control 9.2.1 Machine Learning 9.2.2 High Rate Cold Spray Manufacturing 9.2.3 Laser-Assisted Cold Spray 9.3 Advanced Cold Spray Materials 9.3.1 Aluminum and Aluminum Alloys 9.3.2 Chrome Plating Replacement 9.3.3 Composite Materials 9.3.4 Polymer Applications 9.4 Joining of Dissimilar Materials 9.4.1 Importance of Magnesium 9.4.2 Practicality and Advantages of Cold Spray 9.4.3 Joining of Aluminum to Magnesium 9.4.4 Applications of Joining Aluminum to Magnesium 9.4.5 Testing Joint Integrity 9.4.6 Discussion 9.5 3D Additive Manufacturing 9.5.1 Conforming Material onto a Substrate 9.5.2 Additive and Subtractive Manufacturing 9.5.3 Freeform Manufacturing 9.5.4 Challenges in Cold Spray 3D Additive Manufacturing 9.6 Cold Spray System Developments Driven by Application 9.6.1 Capillary Cold Spray 9.6.2 Nozzle Design 9.6.3 On-Demand Field Repair and Portability 9.7 Advanced Cold Spray Facilities 9.7.1 Multi-Axis and Multi-Process Integrated Repair and Manufacturing Cell Concept 9.7.2 Cold Spray Repair and Rebuild Technology Cell (CSRRT Cell) 9.7.3 Hybrid Cold Spray Manufacturing and Repair Cell 9.7.4 Helium Automated Repair and Recovery and Repair Manufacturing System (CS-HARRPS) References 10 Applications 10.1 Introduction 10.2 Aerospace 10.2.1 Repair of Magnesium Aircraft Parts 10.2.2 Miscellaneous Aerospace Applications 10.2.3 Repair of B1 Bomber Forward Equipment Bay (FEB) Panels 10.2.4 B1 Bomber Hydraulic Lines 10.2.5 AH-64 Static Mast Support 10.2.6 Residual Stress 10.2.7 T-700 Engine Front Frame 10.2.8 Landing Gear 10.3 Naval 10.3.1 Pump Housing 10.3.2 Flo-Tork Actuator 10.3.3 Cone Assembly 10.3.4 Periscope 10.4 Automotive 10.4.1 Insulated Gate Bipolar Transistor (IGBT) Baseplates 10.4.2 Selective Galvanizing and Corrosion Protection of Trim 10.4.3 Engine Block Repair 10.5 Electronics 10.5.1 Electromagnetic Shielding 10.5.2 Thermal Management 10.6 Medical 10.6.1 Antimicrobial Coatings 10.7 Additive Manufactured Cold Spray Parts References