Friction-induced construction of PTFE-anchored MXene heterogeneous lubricating coating and its in-situ tribological transfer mechanism

In this work, a surprisingly simple and versatile strategy was developed to construct organic/inorganic bi-layer coating, and excellent lubricating properties and long service life are achieved simultaneously. The PTFE/Al3+-MXene coating was fabricated by a two-step strategy including self-assembly of Al3+-induced MXene coatings and in-situ transfer of PTFE under the induction of friction force and heat, which are designed to promote the molecular interaction and mechanical properties of composite coating, respectively. The ratio of Al3+/MXene concentration and pre-friction time against PTFE ball were regulated and optimized. It was found that the interaction exists between the transferred PTFE layer and MXene layer. Molecular dynamics simulations confirmed that the PTFE molecular chains could be anchored at the oxidation site of MXene sheets through friction-induced molecular welding, slowing MXene’s oxidation diffusion from the edge to the surface. The research results show that PTFE/Al3+-MXene coating after 1.0 h of pre-friction time presents the best service life among the prepared coatings, approximately 9 times longer than the PTFE transfer layer-1.0 h, and also much better than the Al3+-MXene 10 raw coating without transferring PTFE. It was further found that the obtained PTFE/Al3+-MXene/T-1.0 composite coating facilitates the easy formation of secondary transfer film on the upper counterpart, which is critical in extending the wear-resisting life of PTFE/Al3+-MXene/T-1.0 bi-layer coating.