A Molecular Dynamics Study of Boundary Lubrication of Silicate Glass at High Temperatures

This study employs reactive molecular dynamics (MD) simulations to investigate how key operating conditions, such as loading pressure, temperature, and sliding speed, influence the morphological evolution of iron oxide asperities lubricated by sodium silicate glass at increased temperatures. We systematically analyze the formation of wear particles, atom transfer, worn surface area, and tribological responses, such as shear stress and the coefficient of friction (CoF). Notably, this work presents, for the first time, a detailed investigation of asperity wear evolution as a function of sliding distance. The results show that the number of wear nanoparticles, the number of transferred atoms, and worn area differences all increase with sliding distance with their growth rate peaking at a loading pressure before decreasing. These metrics increase with temperature but exhibit a nonmonotonic trend with sliding speed, initially decreasing before reversing beyond a threshold velocity. Consistent with prior MD findings, shear stress increases while the CoF decreases under higher pressures. Conversely, increasing temperatures lead to a nonlinear reduction in both shear stress and the CoF. Interestingly, variations in sliding speed have a minimal impact on the CoF and shear stress. This work provides fresh insights into the wear behavior of lubricated asperities under extreme conditions, with implications for high-temperature tribological applications.