Effects of the content of MoS2 on microstructural evolution and wear behaviors of the laser-clad coatings

Abstract

New self-lubricating laser-clad coatings were successfully fabricated on the surface of Ti6Al4V to improve its wear resistance. A new lubricating phase (TiS2) with a lamellar structure was in situ synthesized to resolve the easy-decomposition shortcoming of commonly used sulfides (MoS2, WS2 etc.) during cladding and high-temperature service. Effects of the MoS2 content in the cladding materials on the coatings' macrophologies and microstructures were revealed thoroughly. The evolution in their microhardness and wear behaviors was also explored in detail. Their wear mechanisms were especially highlighted. Results showed that the microstructures of the coatings with MoS2 less than 6 wt% were nearly identical, in which Ti2Ni, TiNi, TiB2 and TiC were in situ synthesized. However, a new spherical phase (TiS2) was in situ synthesized and its volume fraction presented the increasing trend with the increase in content of MoS2 from 6 wt% to 10 wt%. Accompanied with the change, the friction coefficient fluctuated more slightly along with the change in sliding time and its average value was also lower in the stable wear stage. Their wear volumes were similar (about 0.6104 mm3 for 0 wt% MoS2, 0.6408 mm3 for 4 wt% MoS2 and 0.5889 mm3 for 6 wt% MoS2). The wear volumes of the coatings with 8 wt% and 10 wt% MoS2 were significantly reduced to 0.3624 mm3 and 0.2686 mm3, respectively. TiS2 with anti-friction and protection roles can be in situ synthesized in the laser-clad when MoS2 involved in the cladding material exceeds the threshold value of 6 wt%, which significantly improves wear resistance of Ti6Al4V.