Cold Spray

Cold spraying, formally gas dynamic cold spraying, is a coating process that builds up a metal, polymer or ceramic layer on a surface without melting the coating material at all: fine solid powder particles, typically one to fifty micrometers across, are accelerated by a supersonic gas jet to speeds of roughly 1,200 meters per second and driven directly into the substrate, where the kinetic energy of impact deforms the particles plastically and welds them mechanically to the surface. Because nothing is melted, cold spraying can apply coatings of materials that would oxidize, decompose or lose their engineered microstructure if heated the way conventional thermal spraying heats its coating material. The technique was developed by researchers in Russia in the 1990s, discovered when particles being used in wind-tunnel erosion experiments were observed forming an unexpected coating on the test surface rather than eroding it, and it was commercialized soon afterward for applications where heat-sensitive coating materials made older thermal spray processes unsuitable.