Triboscopic Insights into Long-Term Tribologic Behavior of Brass/ta-C in High Vacuum

Abstract

It is widely known that tribological systems operating in vacuum environments face significant challenges. MoS2 is a well-known material for its low friction properties in both ambient and vacuum environments. However, it has a low wear resistance and a limited ability to withstand higher contact pressures. A possible alternative to MoS2 are super-hard hydrogen-free tetrahedral amorphous carbon coatings (ta-C). In normal atmospheric conditions, they have low friction and wear properties, but their performance in vacuum is limited. In this work, ta-C coatings are paired with brass in high vacuum conditions. Long-term tribological performance tests are conducted and analyzed using triboscopic imaging. It was found that the brass/ta-C friction pair exhibited an increase of the friction coefficient in the long term (up to 0.52) due to a change in wear mechanism. Different wear and healing behaviors could be found for both the brass counterbody and the ta-C discs using triboscopy.