Investigations Of Microstructures And Tribological Properties Of MoS₂-Ti Solid Lubricating Films In LEO Environment

Due to the significant difference between the working environment in oribit andground, the effective spatial lubrication technology is indispensable for the ensurance ofthe spatial mechanism with high reliability and the expected life span in Low Earth Orbit(LEO). MoS2-Ti solid lubricating films deposited by unbalanced magnetron sputteringdeposition were studied in this paper. FESEM, EDS, AFM, XRD, Raman spectrometer,3D confocal microscope and nano indentation hardness tester were applied to investigatedthe morphologies and properties of MoS2-Ti films. The effects of high-energy protons andatomic oxygen irradiation with different doses on the structure and properties of MoS2-Tifilms were focused on. The tribological behaviors in vacuum before and after irradiationwere investigated by changing the experiment conditions, and the effects of variable loadon the friction and wear properties were discussed. The specific results are as follows:MoS2-Ti solid lubricating films are dense with preferred orientation of (002) planeand possess the surface like the gathered cauliflower. The indentation hardness and elasticmodulus is3.85GPa and84GPa, respectively. MoS2-Ti films possess good adhesion tosubstrate and excellent lubrication performance in the high vacuum environment.The displacement damage exists in the proton irradiation on MoS2-Ti films. Thelonger the irradiation time, the more serious damage of surface coarsening caused bydisplacement damage. Atomic oxygen irradiation can denudate MoS2-Ti films. The longerthe irradiation time, the more serious damage of surface coarsening caused by denudationeffect. The vacuum coefficient of friction before and after the proton irradiation andatomic oxygen irradiation the film were studied by changing the load (2N,4N,6N) andsliding speed (0.2m/s,0.4m/s,0.6m/s), respectively. The results show that, under the highvacuum environment, the wear mechanisms after proton irradiation are mainly abrasivewear and adhesive wear, while after atomic oxygen irradiation, the wear mechanisms aremainly abrasive wear, adhesive wear and fatigue wear.The simulation of actual working condition were applied with three different variableload methods: sine wave, square wave and sawtooth wave. Under the loads with sine wave,the average film friction torque is0.045N/m, and the wear mechanism is mainly adhesive wear. Under the loads with square wave, the average film friction torque shows a trend ofdecrease, the average friction torque is0.019N/m, the wear mechanism is mainly furrowswear. Under the loads with sawtooth wave, the average film friction torque is0.02N/m,the mechanism is mainly dominated by brittle spalling.