Microstructure and properties characterization of Ti-containing Ni60/Graphite self-lubricating composite coatings applied on 300M ultra-high strength steel by laser cladding

Abstract To improve the wear and corrosion resistance of 300M ultra-high strength (300M) steels, the Ni-based alloy (Ni60)/nickel-coated graphite composite coatings with the addition of titanium (Ti) were claded on 300M by laser. The microstructure, micro-hardness, tribological performance, corrosion resistance, thermal property, and dynamic mechanical property of the coatings were characterized. The cladding-layer microstructure of the Ti-containing (6 wt% Ti) coatings showed an equiaxial tendency. The microhardness of the Ti-containing coatings was higher and more homogeneous. The wear rate of the matrix was 29.4 times higher than that of Ti-containing composite coatings and was 2.4 times larger than that of the Ti-free (0 wt% Ti) composite coatings. However, the friction coefficient of the Ti-containing composite coatings was higher than that of the Ti-free composite coatings. The self-corrosion current densities of the Ti-containing, Ti-free composite coating and 300M were 0.25, 3.16 and 232.51 μA/cm2, respectively, indicating that the corrosion resistance of Ti-containing composite coatings was improved. The impact-resistance of the Ti-containing composite coatings was better than that of the Ti-free composite coatings.