Hyperthermal atomic oxygen interaction with MoS{sub}2 lubricants and relevance to space environmental effects in low earth orbit - effects on friction coefficient and wear-life

摘要

Wear-life of the MoS{sub}2 film was evaluated by in situ tribological testing under 5 eV atomic oxygen exposures which simulated atomic oxygen environment in low Earth orbit. A combination of a laser-detonation atomic oxygen source and a conventional pin-on-disk friction tester was used to perform tribological tests. It was confirmed that the friction coefficient was not affected by atomic oxygen exposure when atomic oxygen fiuence was low; however, the friction coefficient increased with increasing atomic oxygen fluence and it reached as high as 0.05 at the atomic oxygen fiuence of 3.4 × 10{sup}16 atoms/cm{sup}2/cycle (nine times larger than the normal value). Effect of atomic oxygen on the wear-life of the film has much more drastic With atomic oxygen fluence of 1.7 × 10{sup}16 atoms/ cm{sup}2/cycle, wear-life of the film was reduced less than one-tenth of that during ex situ testing result of the same film. It was also observed that the wear-life of the film was inversely proportional to the atomic oxygen fluence between sliding passes.