Microstructure, microhardness and corrosion resistance of laser cladding Ni–WC coating on AlSi5Cu1Mg alloy

The microstructure, microhardness, and corrosion resistance of laser cladding Ni–WC coating on the surface of AlSi5Cu1Mg alloy were investigated by scanning electron microscopy, X-ray diffraction, microhardness testing, immersion corrosion testing, and electrochemical measurement. The results show that a smooth coating containing NiAl, Ni3Al, M7C3, M23C6 phases (M=Ni, Al, Cr, W, Fe) and WC particles is prepared by laser cladding. Under a laser scanning speed of 120 mm/min, the microhardness of the cladding coating is 9–11 times that of AlSi5Cu1Mg, due to the synergistic effect of excellent metallurgical bond and newly formed carbides. The Ni–WC coating shows higher corrosion potential (−318.09 mV) and lower corrosion current density (12.33 μA/cm2) compared with the matrix. The crack-free, dense cladding coating obviously inhibits the penetration of Cl− and H+, leading to the remarkedly improved corrosion resistance of cladding coating.