Residual Stress and Corrosion Resistance of Aluminium Coatings Deposited by Cold Spray

摘要

Cold Gas Dynamic Spray or simply Cold spray, is gaining more interest than conventional thermal spray techniques primarily because of the lower deposition temperature required to deposit metallic and composite coatings [1]. Cold spray does not use a heat source, such as the conventional thermal spray processes, but instead uses a high-pressure gas jet to accelerate particles to supersonic speed through a convergent-divergent DeLaval nozzle so that the particles achieve sufficient kinetic energy to undergo plastic deformation on impact, fig. (1) show the main operation of a coldpsray system: first of all the carrier gas is inlet at high pressure (pressure up to 3.0 MPa could be achieved) to the system. Then, the main part of the gas flows through a heating system while a minor part of the gas goes through the powder feeder and drags the particles to the nozzle. The two flows come together at the entrance of the nozzle and they are accelerated to supersonic speed thanks to the converging-diverging De Laval nozzle. The gas temperature ranges typically between 200 and 800 °C but the particle temperature is highly slower because of the very short time in which they get in contact with the gas so the coldspray process does not involve bulk melting and the material is mostly produced entirely in the solid state [1].