Process optimization, microstructure characterization, and tribological performance of Y2O3 modified Ti6Al4V-WC gradient coating produced by laser cladding

In this study, the two layers Ti6Al4V-based wear-resistant coatings with a gradient WC structure were produced on a Ti6Al4V substrate by laser cladding. The cladding parameters were optimized by setting the range and gray relation analyses. Furthermore, a comprehensive study was performed on the microstructure and phase composition of the gradient coatings. Particularly, the hardness, tribological performance, and strengthening mechanism of the coating were explored. Results reveal that the gradient coating mainly contains TiC, Ti, (Ti,W)C and TixW(1-x) solid solution with minor Y2O3. The coating not only has a gradient structure but also shows a gradually decreasing trend in hardness and wear resistance from the top layer to the substrate. Compared to the Ti6Al4V substrate, the bottom and top of the coating show 34.9 % and 72.1 % reductions in wear volume, respectively. The improvement of the wear resistance property can be attributed to the formation of reinforcing phases (WC, TiC, (Ti,W)C and TixW(1-x)).