Molecular dynamics simulation and microscale experimental investigation on the tribological interactions between Cu and PTFE

This study investigated the dry tribological interactions between a copper (Cu) indenter and polytetrafluoroethylene (PTFE) at the molecular and microscopic scales through a combined molecular dynamics (MD) and atomic force microscopy (AFM) experiments. The interfacial adhesion force ratio between Cu–Cu and Cu–PTFE was quantitatively verified to be approximately 5:1 across both scales. Deconvolution of the friction components indicated that adhesion dominated in the Cu–Cu system due to metallic bonding, whereas friction in the Cu–PTFE system was primarily governed by mechanical plowing effects, with interfacial adhesion playing only a secondary role. By monitoring Von Mises stress, surface morphology, energy and temperature, friction force and wear rate, the molecular dynamics mechanism underlying the plowing effect were revealed, tracing the transition from chain entanglement and stretching to bond fracture and debris formation. Furthermore, the simulations reveal that increasing indentation depth, indenter radius, and scratching speed intensifies stress concentration and molecular deformation. The wear rate exhibits a linear relationship with sliding distance, confirming the applicability of Archard’s law at the single-asperity nanoscale. It was also found that the wear performance of PTFE is more sensitive to penetration depth than to asperity radius. AFM experiments further confirmed that as the scratching speed and normal load increased, the friction and wear of PTFE gradually increased. This work provides a simulation and experiment routine for disclosing wear mechanism of water-lubricated materials.