Effect of Long Time Orbit Exposure Test on Solid Lubricative Coating

概要

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Moving components materials in orbit environment require surface modification with stable lubrication for preventing increase in friction due to oxidation and irradiation damages. We have prepared a stainless steel substrate and four kinds of lubricative coatings such as TiN, MoS2, mixture of Cu and BN and Cu on the substrates and installed them on the International Space Station in orbit for exposure test from about a year to three years. We have analyzed tribological properties, surface roughness, chemical concentration and so on. Most of substrates exposed for one year decreased their friction in vacuum as well as at atmospheric pressure, whereas most of substrates exposed for two and three years increased their friction. XPS analysis shows Si based contamination layer that might affect the change in tribological properties.