Numerical Investigation On The Deformation Behavior Of Cold Sprayed Particles And Substrate

Cold spraying is a new coating deposition technology which has been developing during the past two decades. Solid particles are accelerated to a high velocity by using a supersonic gas jet. A coating is formed through intensive plastic deformation of particles impacting on a substrate at a temperature well below the melting point of spray material. As a consequence, the deleterious effects of high-temperature oxidation, melting, residual stresses, and other common problems for traditional thermal spray methods are minimized or eliminated.In this study, a comprehensive investigation on particle deformation behavior in cold spraying was conducted by numerical method. A number of key issues of the initial temperature, collision angle, friction, as well as the deformation behavior of multi-particle collision substrate were studied in this paper. Numerical simulation results show that:The initial temperature of particles and substrate has a greater impact on the deformation behavior. The higher the initial temperature, the greater the contact area, and particle deformation is more severe, so that to raise initial temperature can increase the contact area, which can make particles completely embedded in the substrate and enhance bonding strength. In the process of numerical simulation, the temperature in the collision process don’t exceed melting point of spraying material, showing that melting is not the primary combination way of particle and substrate.The existence of contact interface friction will increase local temperature, and the squeeze effect of this friction is also conducive to the destruction of oxide layer of substrate and particle, and prompt fresh metal contact with each other, thereby improve the efficiency of combination of particles and substrate. When the spray angle exceeds20°, the positive role played by friction is offset by the negative role played by particles slip effect, and the contact area is reduced which is not conducive to the combination of particles and substrate.The subsequent incident particles can tamp the formed coating, which makes the final formed coating present sparser near the surface and denser inside the deep layer. Thus increasing the thickness of coating can also improve the quality of coating. The sputtering formed during the process of particles impact substrate is not conducive to the deformation of subsequent incident particles and increase the porosity of the coating especially the surface, due to the weak role of compaction which subsequent incident particles played, the pores are mainly concentrated in the surface of the coating. The coating structure formed by different materials of spray particles is not the same, the spray material of copper whose elastic modulus and yield limit are low form more metal sputtering, and particle deformation is more intense. Stainless steel whose yield limit and elastic modulus are higher forms a less sputtering and the coating formed by stainless steel has less pores.