Preface

Cold spray refers to a material-deposition technique that uses a supersonic particle jet. In the high-pressure cold spray (HPCS) process, gas and powder are mixed upstream and expanded via de Laval nozzle to produce a supersonic particle jet, which produces coatings based on a wide selection of materials with superior characteristics and high deposition efficiency. Although some systems (low-pressure cold spray) use subsonic particles laden with a peening agent to process ductile materials with acceptable properties, these systems are not covered in this book.

In a short span of approximately 20 to 25 years, cold spray has moved from a scientific curiosity carried out in a few research establishments to an established and integral manufacturing process, adopted in multiple high-tech industries. Homemade spray systems have been replaced with a selection of vendor-supplied commercial systems. Special powders with specific characteristics, required for cold spray processing, are readily available.

Around the globe, scientists and engineers have taken up both basic and application research and development (R&D) activities in universities, national laboratories, and industries. These activities have resulted in advancements in all aspects of the technology, including basic science of gas/particle interaction, particle impact and coating generation, parameters/processing/properties relationships, and performance of coatings in various industrial environments. These advancements have led to a multitude of applications, from protective and performance-enhancing layers to repair and refurbishing of parts to fabrication of components by near-net shaping or additive manufacturing techniques. The number of industries adapting to cold spray technology is growing rapidly, from automobile to aerospace to turbine and power to defense to sputter targets and others.

Enormous growth in R&D activities has led to a huge databank in the form of publications in peer-reviewed journals and conference proceedings. However, consolidated information on all aspects of cold spray technology in book form is hard to find. This book covers the need for consolidated information, with focus on applications in specific industries. Experts around the globe have contributed in their specific areas of specialties.

The basic science and modeling of the cold spray process are discussed in the first few chapters, which are followed by details of equipment and powder supply. The second half of the book concentrates on cold spray applications in various industries. Experts from each industry have written about applications in their specific industries.

We have tried to eliminate repetition of specific applications in multiple chapters. However, some applications present themselves in many industries. For instance, the defense, aerospace, and power-generation industries require repair/refurbishment of turbine components and are treated by industry experts in their respective chapters from their perspectives.

We offer our deepest thanks to all those who have contributed to this publication. The time, effort, and professionalism represented by the commitment to authoring these chapters is the culmination of relationships developed out of a shared passion for cold spray technology—relationships built at airports and conferences, via emails, in hotel lobbies, and through many joint development initiatives. It is both a professional and personal honor for us to work with those who are held in the highest regard for their expertise, sincerity, and time to contribute.

The reader will find this book a useful assembly of information. The substantial information provided by the authors will serve as a resource that may lead the reader in many directions, both in the principles of HPCS and in applications in which the unique properties of cold spray have developed by providing both exceptional surfacing solutions and additive manufacturing applications.

Our authors have focused on cold spray, a field in which their work has reached all corners of the world as a result of their knowledge and working relationships. Included within these chapters are references showing a cross section of true scientific research, from materials development to practical applications.

We acknowledge that these authors, in making their contributions to this book, have spent substantial amounts of time persevering in the task of documenting their knowledge. We believe the chapters contained within this book will easily demonstrate the truth of our acknowledgment and greatly add to the reader’s knowledge of cold spray.