Preparation, Microstructure And Properties Of WS₂/W-DLC Composite Solid Lubrication Film

With the purpose of improving the tribological property of W doped diamondlike carbon (W-DLC) film, on the basis of the coating concept of multilayer, twoseries of WS2/W-DLC composite solid lubrication films were prepared using hybriddeposition techniques in combination with low temperature ion sulfurizationtechnique, including hydrogenated and hydrogen-free WS2/W-DLC composite solidlubrication coatings. The tribological property of the films before or after thetreatment was investigated by a MS-T3000friction and wear tester. SEM and three-dimensional light interfering profilometer were employed to observe themorphologies of surface of films, XRD was adopted to detect the surface phasestructure. Raman was adopted to characterize the structure of C atoms and XPS wasused to identify the valence state of different elements of the films. The influence ofW concentration on the micro-morphology, composition, microstructure, mechanicaland tribological property of the coatings were investigated. The results were shown asfollowed:(1) The hydrogenated WS2/W-DLC composite solid lubrication films werefabricated by ion beam deposition+magnetron sputtering techniques in combinationwith low temperature ion sulfurization. The surfaces were smooth, only with somenanoscale particles. With the increasing of W concentration, the content of sp2increased, however the formation of hard nanoparticles WXC in carbon matrix to forma nanocomposite structure led to an enhancement in hardness. Graphitization and WS2was formed on the surface of W-DLC film after ion sulfuration, which made thehardness of W-DLC film decreases. The optimum wear performance with frictioncoefficient of0.19and wear rate of1.65×10-7mm3/Nm was achieved for27.7%WS2/W-DLC film.(2) The hydrogen-free WS2/W-DLC composite solid lubrication film wasprepared by ion beam assistant deposition technique in combination with lowtemperature ion sulfurization. All the surfaces were nanoscale and without defect. Theroughness was lower than30nm after ion sulfurization. The hardness and elastic modulus of the films were increased gradually, as the W target current increased.After ion sulfurization the hardness decreased, due to the formation of metal sulfidesand graphite-rich composite solid lubrication layer on the top surface. The lowestfriction coefficient0.107and wear rate2.37×10-7mm3/Nm were achieved from thesample at W target beam current of75mA.(3) The metal sulfides and graphite-rich composite solid lubrication layer on thetop surface contributed to the friction-reducing and wear-resistence. After ionsulfuizeation, the harder sublayer can provide a strong support for the softer WS2andgraphite-rich toplayer. Under dry friction condition, high W content WS2/W-DLCcomposite solid lubrication film decreased the contact area and plastic deformation,which led to reduce the friction and wear rate efficiently.