In Situ Tribochemical Reconstruction of Ti₃C₂T_x Enables Low Friction in Oil-Lubricated Steel Contacts

MXene has emerged as a promising two-dimensional (2D) lubricant additive due to its layered structure, low interlayer shear strength, and tribochemical activity. However, their structural instability under oxygen-containing and high-temperature conditions often leads to oxidation and decomposition, which severely limits their practical use in lubrication systems. In this study, instead of suppressing this transformation, we harness the tribochemically induced in situ evolution of MXene to construct a self-adaptive lubricating interface for low friction and wear under oil lubrication. Comprehensive interfacial characterizations reveal that tribological loading drives the transformation of MXene into a highly graphitized carbon-rich tribofilm, while coordination interactions between oleic acid (OA) and MXene facilitate carbon reconstruction at the sliding interface. Reactive molecular dynamics (RMD) simulations further demonstrate that friction-induced shear promotes Ti-C bond dissociation and carbon graphitization, providing atomistic insights into the dynamic interfacial reconstruction process. The combined effects of tribochemical transformation and molecular coordination promote the formation and progressive reconstruction of a robust graphitized tribofilm, thereby sustaining low friction and enhancing wear resistance. This work provides new insights into the tribological behavior of MXene-based additives and highlights their potential for high-performance lubrication in advanced mechanical systems.