The aim of this study is to determine how feedstock shape affects deposition efficiency and coating formation in cold spraying. Spherical and irregular-shaped Cu powders were sprayed on Al substrates at gas temperatures ranging from 100 to 650 °C. Rebound particles were collected and examined and various coating qualities were assessed, including deposition efficiency, hardness, stack morphology, and adhesion strength. In order to explain certain discrepancies between predicted and measured data, as-sprayed and heat-treated coatings were compared and powder hardness was analyzed in detail. Contrary to simple theoretical hydrodynamic simulations, the critical threshold velocity for irregular particles was higher than that of the spherical ones. The results and practical implications of the study are discussed in the paper.

Post-annealing of cold spray coatings has great potential for wear applications because it produces intermetallic compounds at low temperature far below equilibrium. This study investigates the effects of spraying pressure on the intermetallics formed and their dispersion characteristics. In the experiments, Al and Al-Ni powders were sprayed on Ni and Al substrates at 0.7, 1.5, and 2.5 MPa and a portion of the coating samples were annealed in argon at 500, 550, and 600 °C. Detailed examinations showed that Al particles are subject to peening effects that can interfere with the formation of intermetallic compounds during annealing, but that the effects can be mitigated by controlling gas pressure. Spraying pressure was also found to have an effect on the formation of eutectic pores in Al-Ni composite coatings, with higher pressures corresponding to fewer pores.