Tribological behaviors of hydrogenated diamond-like carbon films in different testing environments

摘要

Hydrogenated diamond-like carbon (DLC) films were deposited on Si substrate using plasma enhanced chemical vapor deposition(PECVD) technique with CH_4 plus H_2 as the feedstock. The tribological properties of the hydrogenated DLC films were measured on a ball-on-disk tribometer in different testing environments (humid air, dry air, dry O_2, dry Ar and dry N_2) sliding against Si_3N_4 balls. The friction surfaces of the films and Si3N4 balls were observed on a scanning electron microscope (SEM) and investigated by X-ray photoelectron spectroscopy (XPS). The results show that the tribological properties of the hydrogenated DLC films are strongly dependent on the testing environments. In dry Ar and dry N_2 environments, the hydrogenated DLC films provide a superlow friction coefficient of about 0. 008 -0. 01 and excellent wear resistance (wear life of above 56 km). In dry air and dry O_2, the friction coefficient is increased to 0. 025 - 0. 04 and the wear life is decreased to about 30 km. When sliding in moist air, the friction coefficient of the films is further increased to 0. 08 and the wear life is decreased to 10. 4 km. SEM and XPS analyses show that the tribological behaviors appear to rely on the transferred carbon-rich layer processes on the Si_3 N_4 balls and on the friction-induced oxidation of the films controlled by the nature of the testing environments.