Effect of In-situ Softening on the Deposition Behavior of Particles by Controlling Gas Stream Traversing During Cold Spraying

Abstract

Abstract The deposition behavior of particles during cold spraying is determined by plastic deformation of both substrate and impinging spray particles. In this paper, the in-situ heating and subsequent softening of the local substrate were examined to reveal their influence on the deposition behavior of spray particles and the microstructure and property of the cold-sprayed 316L stainless steel and copper coatings. Results show that the temperature of the substrate surface, where the spray gas stream and high velocity particles were projected on, increased to 300°C when the gas temperature was 500°C. Such effect is referred to as the in-situ substrate heating. The in-situ heating of the substrate surface was enhanced with the decrease in the gun nozzle traverse speed. With the decrease of nozzle traverse speed from 100 to 20 mm/s, the relative deposition efficiency significantly increased and the porosity of cold-sprayed 316L coatings decreased from 5.6% to 2.5%, and the micro-hardness of the coatings increased from 283 Hv to 351 Hv. The influence of the nozzle traverse speed on the microstructure and property of cold-sprayed coatings is discussed based on the influence of the in-situ heating and softening effect of substrate surface on its deformation behavior and particle deposition upon the impact of spray particles. The in-situ substrate surface heating is proposed as an essential processing parameter as a function of gun traverse speed during cold spraying.