Fabrication and tribological properties of laser cladding WC-Cu/Co-based composite coatings

Abstract

Different proportions of WC/Cu particle-reinforced Co-based composite coatings were successfully prepared by laser cladding on the Inconel 718 superalloy to investigate their tribological properties sliding against the Si3N4 ball at room temperature (RT) and 600 °C. The results show that the addition of WC and Cu can serve to improve the microhardness and tribological properties of the composite coatings. The composite coatings demonstrated a greater than 1.7-fold increase in microhardness as compared to the substrate, which was mainly attributed to the grain refinement of the coatings resulting from the γ-Co phase and intergranular eutectic structure, and the presence of hard phases, such as WC, FexNby and Cr2C3. Notably, the 5wt.%WC and 5wt.%Cu additives obviously raise the wear resistance of Co-based composite coating, in which significant decreases in wear rates are attained under RT (∼84.4 %) and 600 °C (∼64.9 %). In addition, excellent friction-reduction abilities are also found in the Co-5wt.%WC-10wt.%Cu coating at RT and Co-5wt.%WC-15wt.%Cu coating at 600 °C, with corresponding friction reductions of about 30.8 % and 26.7 %, respectively. The main wear mechanisms of coatings were found to be oxidative and fatigue wear at RT; oxidative and adhesive wear at 600 °C.