Warm Spray Technology: Historical Review and Future Prospects

Warm Spray (WS) was developed in Japan at the National Institute for Materials Science (NIMS) in 2006. It was conceived as a process of taking advantage of thermal softening of spray materials for easier bonding formation while controlling excessive degradation associated with melting in conventional thermal spraying. The process was realized by modifying a HVOF process by inserting a gas mixing chamber to blow in inert gas such as nitrogen between the combustion chamber and the powder feet ports. Since the operating window in terms of the temperature and velocity of sprayed particles of this process lied in between Cold Spray and HVOF, the term “Warm Spray“ was coined. A wide range of materials have been deposited using WS, including pure metals such as titanium, nickel, aluminum, copper, alloys such as Ti6-4, CoNiCrAlY, SUS316L, cermets such as WC-Co, polymers such as HMWPE and PEEK, and even some nano-grained oxides. In this presentation, a historical review will be given on the process development and application to various materials as mentioned above. A critical assessment of the process and the deposited coatings will be given to discuss about future prospects of WS.