Regulation mechanism of transfer film on fretting regime via self-mated and hetero-mated diamond-like carbon films

Abstract

Self-lubricating solid films have been demonstrated to be effective in substantially reducing fretting wear. However, different films exhibit diverse fretting behaviors under different fretting running states. Therefore, it is of utmost importance to explore the friction-reduction mechanisms of self-lubricating films in different fretting regimes. The fretting behaviors of two solid lubricating systems, namely the Diamond-like carbon (DLC)/DLC self-mated pair and the molybdenum disulfide (MoS₂)/DLC hetero-mated pair, were evaluated. A detailed investigation was conducted on their fretting wear performances in different fretting regimes. Based on the research on transfer films, the fretting wear mechanisms were summarized. The research findings reveal that the DLC/DLC friction pair can efficiently transfer the DLC film on the substrate surface to the counterpart ball surface with low wear and dissipated energy, forming a transfer film with a higher degree of graphitization. In contrast, when amorphous carbon and MoS₂ are completely intermixed, the DLC/MoS₂ friction pair forms a transfer film with the co-presence of the layered structure of MoS₂ and amorphous carbon with a high sp² content. Their different formation mechanisms and structures are the key determinants for the discrepancies in the fretting behaviors of the two friction pairs within distinct fretting regimes. Consequently, by implementing diverse friction pairs to introduce distinct solid lubricating films, precise manipulation of the friction interface and the structure of transfer film can be achieved. This approach is designed to optimize the fretting performance, ensuring enhanced friction reduction and anti-wear capabilities across various fretting regimes.