Thermal Spray: Thermal Spray refers to a broad class of processes in which molten droplets of metals, ceramics, glasses, and/or polymers are sprayed onto a surface to produce a coating, form a free-standing near-net shape, or create engineered materials with unique properties, e.g., strain-tolerant ceramics, metallic glasses, cermets, and metal/polymer composites (plastimets). Thermal spray is a powerful and versatile technology.
Almost any material with a stable molten phase can be deposited, and relatively thick coatings (0.1-10+ mm) can be sprayed onto a wide range of substrates at high deposition rates. Commercially important applications include aerospace, power generation, petrochemical, automotive, marine, biomedical, computers, electronics, paper making, printing, and textiles.
Highly dissimilar materials can be combined using thermal spray. Here, tungsten (Tm = 3400 °C) is sprayed onto aluminum (Tm = 660 °C) without melting the aluminum.
Cold Spray: Cold spray is an emerging technology developed in Russia. Solid powder particles at or near room temperature are accelerated to velocities in the range of 500 to 1,500 m/sec in a supersonic gas jet. Upon impact with a workpiece surface, these high-velocity "cold" particles plastically deform and bond with the underlying material by a process thought to be similar to explosive welding, but on a much smaller scale. Cold spray can be used to deposit a wide range of metals and other ductile materials at high rates. For example, steel and other metal alloys can be cold sprayed onto aluminum or other comparatively low-melting materials to locally increase hardness or wear resistance. Because the process occurs essentially at room temperature, copper, aluminum, and many other reactive metals can be cold sprayed in an open-air environment with little or no oxidation. Because they generally contain fewer oxide impurities and less porosity, cold-sprayed materials typically have much higher thermal and electrical conductivities than traditional, thermally sprayed materials. Sandia has formed an industrial consortium to foster research and commercialization of this exciting new technology.