Properties of Nanostructured WC-12Co Coatings Sprayed by HVOF

Abstract

In the present paper, nanostructured, multimodal and conventional WC-12Co cermet coatings were deposited by HVOF and the properties and structures of the coatings such as microhardness, microstructure, phase composition and wear resistance were compared. Finally the wear failure mechanisms of WC-12Co coatings were explored by XRD and SEM analysis. Research results show that microstructures of nanostructured and multimodal WC-12Co coatings deposited by HVOF are dense with little porosity, and their microhardness values are obviously higher than conventional WC-12Co coating. As well, it was found that nanostructured and multimodal WC-12Co coatings exhibited better erosion and adhesive wear resistance in comparison with conventional coating, and nanostructured WC-12Co coatings possessed the best erosion resistance properties at large impact angles and adhesive wear resistance. At small impact angles, WC-12Co coatings deposited by HVOF demonstrate better erosion wear resistance than at large impact angles and the erosion wear performance at 30º is more than 1.7 times higher than at 90º. In comparison with conventional WC-12Co HVOF sprayed coating, the adhesive wear resistance of the nanostructured and multimodal coatings is respectively enhanced by above 70% and 50%. Testing results also show that although decarburization of WC occurred during spraying multimodal and nanostructured WC-12Co powders, the decarburization of WC for the nanostructured powder was more severe.