Microstructure and mechanical properties of low-pressure cold-sprayed (LPCS) coatings

In low-pressure cold spraying, compressed air is used as a process gas. The most important process parameters are temperature and pressure. In the Low-Pressure Cold Spraying (LPCS) system in this study, the maximum preheating temperature is 650 °C and pressure is 9 bar. Powders used in LPCS process contain alumina with metallic powders; therefore LPCS is the method to spray soft metallic coatings with ceramic hard phase for different application areas, e.g., thick coatings and coatings for electrical and thermal conduction and corrosion protection applications. The aim of this study was to investigate microstructure, denseness, and mechanical properties of LPCS Cu, Ni, and Zn coatings. LPCS coatings seemed to be dense according to Scanning Electron Microscope (SEM) studies but corrosion tests were needed to identify the existence of porosity. Through-porosity was observed in structures of the LPCS coatings. Bond strengths of LPCS Cu and Zn coatings were found to be 20-30 MPa, and hardness was high indicating reinforcement and work hardening.