Impact of thermal cycles on tribological properties and oxidation of MoS2 coatings

Abstract

MoS2 based solid lubricants are extensively used in space applications, where the materials are exposed to large fluctuations of temperatures. Storage takes place in ambient conditions and so does testing, to test the mechanical systems in the harshest environments. In this work, the coatings were exposed to 40 °C, 75 °C and 250 °C for 1 hour and cooled in air to determine the effect of exposure to increased temperature. It was confirmed that MoS2/Ti is thermally stable and not significantly affected by heat treatments. Pure MoS2 observes increased strain in the structure after exposure to 250 °C, which is due to oxygen substitution that takes place in S vacancies, followed by oxide formation. Although coefficient of friction is not affected by heat treatments, wear is reduced due to increase in hardness.