Low friction and environmentally stable diamond-like carbon (DLC) coatings incorporating silicon, oxygen and fluorine sliding against aluminum

► Tribological mechanisms of a-C:H:Si:O:F coating sliding against Al were elucidated. ► a-C:H:Si:O:F exhibited low friction against Al in ambient air and vacuum. ► Cross-sectional analysis revealed SiOx and AlF3 in the carbonaceous transfer layer. ► Passivation of carbon layers by H, F and SiOx by OH reduced the friction. ► Moisture independent friction properties attributed to hydration of SiOx groups.