Effect of Particle Velocity on Cold Sprayed Stainless Steel Deposits

Cold spraying is a new emerging coating technology and has been widely used to produce various material coatings. It has been widely accepted that particle velocity prior to impact is one of the most important parameters for cold spray process, and bonding occurs when the impact velocities of 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 powder with different size or morphology were utilized to prepare coatings and measure particle velocity. Thanks to the non-clogging nozzle developed in PLASMA GIKEN CO., LTD., the particle velocity can be adjusted by the change of working gas pressure and temperature as high as 4 MPa and 1000^oC. The in-flight particle velocity was measured by DPV-2000 system. The microstructure of stainless steel coatings was characterized by optical microscope. The effects of particle size and morphology on particle velocity were discussed, and the relationships between particle velocity and densification of coatings were also investigated.