Cold spray has come to be understood as a materials deposition process in which relatively small particles in the solid state are accelerated to high velocities and deposited on a surface by an impaction process.
Above is a schematic of a typical cold-gas spray system. The process gas is introduced through a gas control module to a manifold system containing a gas heater and powder-metering device. The pressurized gas is heated to a preset temperature, often using a coil of an electrical resistance-heated tube.
The gas is heated not to heat or soften spray particles, but instead to achieve higher sonic flow velocities. The high-pressure gas is introduced into the converging section of a de Laval-type nozzle (i.e., a converging/diverging nozzle). The gas is accelerated to sonic velocity in the throat region of the nozzle, and the flow then becomes supersonic as it expands in the diverging section of the nozzle. The powder feedstock is delivered by a precision metering device and typically is introduced into the high-pressure side of the nozzle in alignment with the throat orifice.
Volume 5A, Thermal Spray Technology -> Thermal Spray Processes and Coatings -> Cold Spray Process -> Cold Spray Equipment and Process Parameters
