Multiscale Investigation of the Anti-Friction Mechanism in Graphene Coatings on Copper Substrates: Substrate Reinforcement via Microstructural Evolution

Graphene exhibits great potential as an anti-friction coating material in MEMS. However, its underlying microscopic friction-reduction mechanism remains unclear. In this paper, the microstructural evolution and nanomechanical behavior of graphene coatings on copper substrates were systematically investigated by AFM friction experiments and MD simulations. MD simulations reveal that the anti-friction properties of graphene coatings primarily stem from microstructural regulation and load-bearing reinforcement of the substrate. The graphene coatings increase indentation diameter by forming transition radii at the indentation edges, and suppress the plowing effect of the substrate by restricting atomic upward movement, both of which enhance the dislocation density and load-bearing capacity of the substrate. Additionally, graphene coatings also reduce the scratch edge angle, weakening the interlocking effect between the substrate and tip, further lowering the friction force. Experimental results indicate that the tribological behavior of graphene coatings exhibits staged characteristics: graphene coatings show excellent ultrafriction properties under intact structural conditions, while showing a higher friction force in wear and tear states. This research provides a theoretical basis and technical guidance for the development of anti-friction and wear-resistant coatings for micro-nano devices.