Effect of molten particle temperature on the bonding formation during plasma spraying of metal alloy coatings

Interface temperature is a determinant factor influencing the bonding formation at the interface between splats, which can be increased by increasing the deposition temperature or particle temperature. However, the oxidation of metallic substrate during the preheating process has a negative effect on the interface bonding. Therefore, the increase of the particle temperature will be the possible way to improve the interface bonding. In this study, the effect of particle temperature on the interface bonding formation between nickel-base alloy splats was investigated. One novel shell-core-structured Mo-clad NiCr powder and conventional NiCr powder were used as the feedstocks. Stainless steel with surface polishing was used as the substrate. Since the temperature of molten NiCrMo particles generated by plasma spraying can reach over 2650oC in comparison with about 2100oCfor NiCr droplets, the molten droplet temperature when it impacts on the substrate surface can be changed continuously through spray distance in above mentioned range. The particle temperature was measured by DPV2000 and the interface bonding state was revealed by the cross-sections of splat-substrate interface prepared by FIB. It was shown that the interface bonding can be increased from ~40% to 90% when the molten droplet temperature is increased from ~2100 oC to 2650 oC.