Microstructure and wear properties of self-lubricating MoS2/Ni coating by laser cladding

Self-lubricating MoS₂/Ni coating was prepared on a medium carbon steel substrate by CO₂ laser cladding using powder mixture of Ni60+50% (wt.%) Ni-coated MoS₂. The chemical compositions and microstructures of the coatings were analyzed using SEM, EDS and XRD. Microhardness was measured on a microhardness tester. The friction coefficient and wear properties were investigated using on a pin-on-ring wear tester. The results show that, during laser cladding process, MoS₂ decomposes to generate some new lubricants such as Cr_xS_1+x and Fe_xS_1+x. Most spherical blocks Cr_xS_1+x exist in the upper section, while white dots Fe_xS_1+x disperse continuously on γ-Ni grain boundary from top to bottom of coating. The coating has a homogeneous microhardness distribution, which is higher than that of the substrate. The friction coefficient of the coating was reduced to 0.09~0.22 in air. The coating wear mass and wear volume was 33.3% and 2.2% of the substrate, respectively.