Tribological behavior and self-lubricating mechanism of Ag–C fiber brushes under air and vacuum conditions

Abstract

Ag–C fiber brushes with high wear resistance and low friction were fabricated by the silver alloy fibers and carbon fibers. The tribological properties of the Ag–C fiber brushes and Ag fiber brush were evaluated, and the worn surfaces of the fiber brushes and coin-silver discs were analyzed to investigate the self-lubricating mechanism of Ag–C fiber brushes. The lubricating films containing C were generated on the worn surfaces, therefore, Ag–50%C fiber brush exhibited a low wear rate of 4.39 × 10−6 mm3/N·m and a friction coefficient as low as 0.297 under vacuum condition. Increasing the applied load increased the friction coefficient and wear rate of the fiber brushes, and the electrical noise and contact resistance had opposite tendency. When the environment changed from air to vacuum, the wear rates of the fiber brushes increased. The electrical noise and contact resistance of the fiber brushes under vacuum were extremely low. The contact resistance of the fiber brushes under air condition was higher than those under vacuum condition due to the existence of the oxide film on the worn surface.