Vacuum brazed Ni-based coating reinforced with core-shell WC@Cu/Co-P

Abstract

Improving the wettability and bond strength of WC with Ni-based matrix and preventing the growth of WC in the melt of Ni-based alloy are always the challenges that should be considered in the fabrication of Ni/WC infiltration brazed coatings. In this research, to improve interface in Ni/WC infiltration brazed coatings, a thin shell of Cu/Co-P was employed. The shell had a thickness of about 80 nm and it was deposited on WC powders by electroless plating. The morphology of WC@Cu/Co-P powders and its microstructure as the reinforcement phase in Ni-based matrix were characterized by field emission scanning electron microscopy equipped with energy dispersive X-ray spectroscopy, and X-ray diffraction. The results showed that this proposed coating had very low porosity, resulting a dense free porosity coating with homogenous distribution of WC. Also, the average growth rate of WC@Cu/Co-P particles was approximately 75 % lower than the same figure for the bare WC particles during liquid phase sintering. These results led to a desirable wear property; the pin on disk test was carried out to investigate the wear behavior of coatings. The wear rate reduction was reduced by 52 % compared to the coatings processed without the shell layer. The average hardness of WC@Cu/Co-P/NiCrBSi coatings was reported about 1590 Vickers, which is 30 % higher than the average hardness of conventional WC/NiCrBSi coatings.