Comparison of Microstructure and Properties between Co-based and Ni-based Gradient Wear-resistant Coating Obtained by Laser Cladding

The alloy powder of St6, St12B was successively fused on the surface of 20CrMnMo steel, then the alloy powder of Co47+5%w(WC) and the alloy powder of Ni60+5%w(WC) was respectively fused on the earlier layer by laser cladding to fabricate the Co-based and the Ni-based gradient wear-resistant coatings with about 2.4mm thickness. The microstructures analysis and properties test of the two coatings were carried out. The results showed that the wear-resistant layer thickness of Co-based is greater than that of Ni-based, the microstructure of two gradient wear-resistant coatings are similar, such as the surface layer appeared the dense amorphous crystals, the transition layer appeared the large columnar crystals, and the bottom layer appeared the flat crystals and dendrites. The microhardness of Co-based wear-resistant layer reached 713HV0.1, and that of Ni-based wear-resistant layer reached 683HV0.1, the friction coefficient of Co-based wear-resistant layer reached 0.4 and that of Ni-based wear-resistant layer reached 0.43, both of the wear resistance increased by 300% compared with the substrate.