Surface Engineering Design of Alumina/Molybdenum Fibrous Monolithic Ceramic to Achieve Excellent Lubrication in a High Vacuum Environment

Abstract

Al2O3/Mo fibrous monolithic ceramics are potential candidates for space applications because of their excellent mechanical properties and low density. This study aims at achieving low friction and long life of this material in a high vacuum environment. Three-dimensional composite-lubricating layers were fabricated by considering texture pattern as storage dimples and MoS2 synthesized via hydrothermal method as lubricant. The tribological properties were studied sliding against Si3N4 ceramic and GCr15 bearing steel balls under high vacuum condition. Results showed that the lubricating properties of the Al2O3/Mo fibrous monolithic ceramics were improved greatly by the micro-texture and MoS2 solid lubricant; the friction coefficients were as low as approximately 0.08 and 0.04, respectively, when Si3N4 ceramic and GCr15 bearing steel balls acted as the pairing materials. It was also demonstrated that the low friction coefficient can be realized with various normal loads and sliding speeds, indicating the composite-lubricating layers have good adaptation of working conditions. This excellent performance of the material is mainly because of MoS2 stored in dimples can be easily dragged onto the friction surface to form lubricating and transferring films during the friction process. This work is an extension of studies that were previously published in Tribology Letters journal.