Abstract:In industrial thermal spray production processes, the workshop and route of powder feeding system needs to be cleaned when changing spraying materials. The powder feeding system include powder feeding tank, powder feeding tray, stirrer, powder feeding pipeline, powder feeding needle. Due to the internal structure of the powder feeding system is complex and the electrostatic adsorption effect, the residual powder in the spray system cannot be completely removed and thus affects the properties of the coating. In this paper, the high-velocity oxy- fuel (HVOF) spray technology were adopted to prepare the MCrAlY coatings on the surface of single crystal substrate, the hereditary behavior in the coatings and the interface between coating and substrate of WC impurity particles (WC-10Co4Cr) remaining in the powder feeding system was studied. The microstructure and phase composition of WC impurities in spray and heat treatment coatings were analyzed by SEM and EDS. The results showed that WC impurity particles exist in the MCrAlY coatings and would be dissolved into coating and even diffuse into single crystal substrate to form new W carbides during heat treatment and oxidation processes. As a result, the microstructure of coating and single crystal substrate has been affected and the local composition uniformity has been changed. Thermocalc software was also used to perform thermodynamic calculations for analyzing the hereditary behavior of W and C elements in the microstructures. If the WC powder and MCrAlY powder shared HVOF spraying equipment, it is recommended to provide MCrAlY powder with a separate powder feeding system to ensure the purity and quality of the coating.