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

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 degrees 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 gamma-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 (similar to 84.4 %) and 600 degrees C (similar to 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 degrees 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 degrees C.