Oil Film Formation and Delamination Process on Nanostructured Surfaces in Boundary Lubrication: A Coarse-Grained Molecular Dynamics Study

A series of coarse-grained molecular dynamics simulations were conducted to investigate the temporal evolution of frictional behaviors of lubricants between sliding nanostructured iron surfaces. Grain boundary atoms were given a stronger interaction with the lubricant molecules. We varied the surface distance and interaction strength between grain boundary atoms and lubricants. It was found that, below the critical compressive stress, the oil film detached from the surface at first and then attached to it after several nanoseconds due to the localized molecular rearrangement within lubricants and the enhancement of interaction between lubricants and iron surfaces. The transition times required for oil film formation and de-lamination both increased as it approached the critical compressive stress. Larger interaction strength increased the delamination time but barely affected the formation time.