Microstructure, dry sliding friction performances and wear mechanism of laser cladded WC-10Co4Cr coating with different Al2O3 mass fractions

To enhance the hardness and wear resistance of cold work mold, Al2O3 reinforced WC-10Co4Cr coatings were fabricated on Cr12MoV steel using a laser cladding (LC). The morphologies, chemical elements and phase compositions of obtained coatings were analyzed using a scanning electron microscope (SEM), energy disperse spectroscopy (EDS), and X-ray diffraction (XRD), respectively. The results show that the Al2O3 reinforced WC-10Co4Cr coatings are composed of Co4W2C, WC and C-depleted W2C phases, and the chemical elements of Al2O3 reinforced WC-10Co4Cr coatings are diffused to the substrate, which form the metallurgical bonding at the coating interfaces. The hardness of WC-10Co4Cr coatings with the 2, 4 and 6% Al2O3 mass fractions increases from 538% to 640% than that of substrate. The average coefficients of friction (COFs) of WC-10Co4Cr-2%Al2O3, -4%Al2O3 and -6%Al2O3 coatings decrease from 71% to 56% than the substrate; and the corresponding wear rates also decrease from 12.4% to 4.2% than the substrate. The average COF and wear rate of WC-10Co4Cr-6%Al2O3 coating are the lowest among the three kinds of coatings, showing that the addition of Al2O3 is the main factor to reduce the COFs and increase the wear resistance of WC-10Co4Cr coatings.