Corrosion and wear resistant WC17Co-TC4 composite coatings with fully dense microstructure enabled by in-situ forging of the large-sized WC17Co particles in cold spray

Although cold spray is a potential alternative to produce high quality Ti-based coatings due to its low process temperature, the cold sprayed Ti or Ti-based alloys usually exhibit a porous microstructure and thus cannot provide effective corrosion protection for the substrate and behave poor wear resistance. In this work, an additional forging/hammering effect for the Ti alloy coatings was introduced by mixing large-sized WC17Co particles into TC4 powder. During spraying, the impact of the large-sized WC17Co particles could plastically deform the deposited TC4 particles and therefore in-situ densify the deposited TC4 coating layer. The embedded WC17Co particles would help to improve the wear resistance of the coating. The effect of WC17Co content in the feedstock powder on microstructure, corrosion and wear performance of the coatings was examined. The porosity of WC17Co-TC4 composite coatings was reduced from 16 % to below 0.5 %. The composite coatings possessed excellent corrosion protection to substrates and the 80 vol.% WC17Co-TC4 composite coating showed the best corrosion resistance. As compared with the pure TC4 coating, the corrosion rate was reduced by 100 times and no corrosion production was observed at coating/substrate interface even after 1000 h salt-fog corrosion test. An increasing trend was detected in wear resistance with the proportion of WC17Co in the feedstock. The 80 vol.% WC17Co coating performed 10 times wear resistance higher than the pure TC4 coating. It is attempted to provide a new approach to develop corrosion and wear resistant Ti and Ti alloy coatings by cold spray.