IN-SITU TRIBOLOGICAL EVALUATION OF GREASES AND SOLID LUBRICANTS IN A SIMULATED ATOMIC OXYGEN ENVIRONMENT

Four greases and nine solid lubricants have been applied to 440C steel surfaces and subjected to in situ tribo-testing in a simulated-atomic -oxygen (SAO) environment. The test apparatus, procedures and results are described. The discussion addresses the calibration of tile SAO tr ibometer using Kapton H film, the effect of SAO on wear and fiction ch aracteristics of unlubricated 440C steel, and the screening test resul ts for all the lubricants under SAO conditions. Endurance test results of selected greases and solid lubricants, such as a PFPE-type grease and MoS2 coatings, are also presented. The results of this research sh ould facilitate selection of effective solid lubricants and greases an d hence lend to improved lifetimes for mechanisms that must operate in the atomic-oxygen environment of low-Earth orbits.