Abstract
To investigate atomic oxygen effects on tribological properties of Mo/MoS2-Pb-PbS film and further enlarge application range, atomic oxygen exposure tests were carried out for 5 h, 10 h, 15 h, and 20 h by the atomic oxygen simulator with atomic oxygen flux of 2.5 × 1015 atoms/cm2·s. The exposure time in test was equivalent to the atomic oxygen cumulative flux for 159.25 h, 318.5 h, 477.75 h, and 637 h at the height of 400 km in space. Then, the vacuum friction test of Mo/MoS2-Pb-PbS thin film was performed under the 6 N load and 100 r/min. By SEM, TEM, and XPS analysis of the surface of the film after atomic oxygen erosion, it was observed that atomic oxygen could cause serious oxidation on the surface of Mo/MoS2-Pb-PbS film, and the contents of MoS2, PbS, and Pb, which were lubricating components, were significantly reduced, and oxides were generated. From AES analysis and the variation in the main element content, Mo/MoS2-Pb-PbS thin film showed self-protection ability in an atomic oxygen environment. Hard oxide generated after atomic oxygen erosion such as MoO3 and Pb3O4 could cause the friction coefficient slight fluctuations, but the average friction coefficient was in a stable state.
Highlights
Friction parts are the important component of space equipment such as manipulator arms, solar arrays, satellite attitude adjustment mechanisms, and driving mechanisms for space exploration instruments and communication antennas, etc. [1,2]
After RF magnetron sputtering and low temperature ion sulfurizing, Mo/MoS2-PbPbS multilayer thin film was exposed to the AO with different incident fluence, and the corresponding composition and structure changes were investigated by SEM and EDS
PbS multilayer thin film was exposed to the AO with different incident fluence, an5dotfh1e2 corresponding composition and structure changes were investigated by SEM and EDS
Summary
Friction parts are the important component of space equipment such as manipulator arms, solar arrays, satellite attitude adjustment mechanisms, and driving mechanisms for space exploration instruments and communication antennas, etc. [1,2]. To improve oxidation resistance and tribological properties of MoS2 film, researchers have explored metal and ceramic incorporated as well as multilayer structures by element doping modification such as Ti, Cr, Au, Al, and Nb [10–12]. The pure molybdenum disulfide film system has been studied by Wang P, the result showed the diffusion of AO can reach 600 nm, which is much higher than the depth of AO at energy (5 eV), and is higher than the 2–5 nm considered in the common literature [13,14] They found that revising the MoS2 lubricant film by doping Ti atoms or especially fabricating in an MoS2/Ti multilayer structure can effectively improve the film resistance to oxidation in AO exposure [15]. The changes in microstructure and friction properties of the film after AO erosion were studied, and the damage mechanism of AO erosion was analyzed
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