Preparation and characterization of WC/Co-W-C cermet coatings with molten zinc corrosion resistance by HVOF spraying of bimodal-structured WC/Co powder

摘要

During continuous hot-dip galvanizing process, the sink rolls are immersed in the molten zinc and corroded seriously by liquid zinc. The WC-based cermet coatings with a Co-W-C ternary phase matrix prepared by HVOF spraying was reported to have an effective zinc corrosion resistance. In this study, WC/Co-W-C coating was developed by HVOF using bimodal-structured WC/Co powder with both micro-sized WC particles and nano-sized WC particles. For comparison, WC/Co-W-C coating was also prepared by HVOF using WC/Co-W-C powder. Results show that the micro-sized WC particles are retained in the coating due to the semi-melting of the spray powder during HVOF spraying. However, the nano-sized WC particles are dissolved in the Co matrix phase to form a Co-W-C ternary phase matrix. Compared to the HVOF sprayed WC/Co-W-C coatings deposited using WC/Co-W-C powders with relatively large WC particles, the coating deposited using bimodal-structured WC/Co powder presents a similar microhardness, better abrasive wear resistance and corrosion resistance.