Synthesis and Triboligical Behavior of Ag-Doped MoS₂ Coatings for Robot Joint

The Ag-doped MoS₂ coatings on 1Cr18Ni9 Ti stainless steel,a good robot-joint material,were synthesized by atmospheric plasma spraying(APS).The influence of the Ag-content on the microstructures and tribological properties was investigated with X-ray diffraction,energy dispersive spectroscopy,scanning electron microscopy,Raman spectroscopy and mechanical probes.The results show that the Ag-doping had a major impact.For instance,Ag-doping increased the compactness,enhanced the interfacial adhesion and decreased pore-size and micro-crack density; Ag and MoS₂ powders easily formed tight clusters at high temperatures.As the Ag-content increased,the friction coefficient significantly decreased,from 0.76 to 0.46 at 20℃ and from 0.32 to 0.13 at 800℃,respectively,accompanied by a considerable decrease of wear-rate.The fact that thermal and/or friction heat possibly induce formation and decomposition of laminar Ag₂MoO₄ and surface segregation of Ag-atoms explains the good lubrication and smooth wear-tracks.