Wear properties of self-lubricating Cr _x S _y /Ni coatings on 304 stainless steel by pre-placed laser cladding

Self-lubricating NiCrBSi–Ni/MoS₂ coatings are prepared on 304 stainless steel by pre-placed laser cladding, in which Ni/MoS₂ is almost completely decomposed and the Cr _x S _y anti-friction phase is in situ generated. Meanwhile, (Cr, Fe)₂B and (Cr, Fe)₇C₃ are generated from the molten pool as a result of oversaturated B and C atoms in γ-Ni and the diffusion of Fe atoms. Therefore, the composite coatings are mainly composed of γ-(Ni, Fe), (Cr, Fe)₂B, (Cr, Fe)₇C₃, and Cr _x S _y. When compared with the substrate, the wear rate of the coatings with 20 wt-% Ni/MoS₂ is reduced by 21.16%, owing to the Cr _x S _y lubricating phase, while it is reduced by 25.61% for the coatings with 5 wt-% Ni/MoS₂, owing to blocky (Cr, Fe)₂B or (Cr, Fe)₇C₃ hard phases. The wear mechanism of the coatings is adhesive wear and oxidative wear.