In-flight particle velocity measurements with DPV-2000 in cold spray

The measurements of in-flight particle velocities and deposition efficiency at cold spraying of two stainless 316L powders having different morphology and almost the same size distributions were carried out. It was found that the angular particle had faster velocity than spherical one and resulted in greater deposition efficiency. The critical velocity of both powders was almost the same and did not depend on their micro-hardness. Therefore, the deposition efficiency was not affected by the particle micro-hardness. The critical velocity significantly depended on He gas temperature and decreased as the temperature increases, but little depended on N2 gas temperature. The critical velocity little depended on operating gas pressure. The cause why the angular particle morphology gives faster velocity in supersonic gas flow compared with the spherical one has to be investigated and clarified. The drag coefficient appears to depend on particle morphology. An angular particle seems to have a larger drag coefficient than a spherical particle.