Investigation of microstructure of laser cladding Ni-WC layer on Al-Si alloy

A plasma-sprayed Ni-WC layer was deposited on an Al-Si cast alloy surface, and then it was further melted by a 5 kW CO2 laser, The microstructure and chemical composition of the laser-melted zone were investigated, and the microhardness in different parts was measured, Experimental results showed that the chemical composition of the sample was not uniform, Compositional segregation in the laser-melted zone was found, Some amorphous structure appeared in the nickel-rich locations after laser melting, Owing to the thermal effect of the laser scanning, an intermediate-phase Ni3Al segregated from this region and formed Ni3Al grains and amorphous grains, Some WC particles melted in the matrix, and chromium carbide Cr23C6 and (Cr,W)C separated during the cooling process. The highest microhardness (1027HV) was found in the high-nickel region.