Abstract
Cold spraying is a new emerging coating technology and has been widely used to produce coatings of various materials. It has been widely accepted that particle velocity prior to impact is one of the most important parameters for the cold spray process, and bonding occurs when the impact velocities of the particles exceed a critical value. As we know, particle velocity is influenced by many parameters, such as nozzle design, particle size, particle morphology, working gas pressure and temperature. In this work, three types of commercial stainless steel powders with different sizes or morphologies were employed to prepare coatings. Their respective particle velocities were also measured. With a non-clogging nozzle developed in Plasma Giken Company, Ltd., the particle velocities can be adjusted by changing the working gas pressures and temperatures to values as high as 4 MPa and 1000°C, respectively. The in-flight particle velocity was monitored via the DPV-2000 system. The results show that the particle velocity was influenced by the working gas pressure, temperature, particle diameter and morphology. Much denser coatings can be obtained with higher particle velocities, and consequently higher micro-hardness values of the coatings can also be achieved.
