The tribological performance of selected solid lubricant films in sand-dust environments

► The sand-dust markedly affects the tribological performance of solid lubricant film. ► The sand particles reduce the COF of film but not increase the wear rate. ► The transferred composite layer plays the vital role in reducing friction and wear. ► The films possess a certain extent sand-dust environmental adaptability. ► A transfer layer-hardening composite model to clarify the wear mechanisms.