Friction dependence on the textured structure of an amorphous carbon surface: A reactive molecular dynamics study

Abstract

Amorphous carbon (a-C) film provides ultralow friction when combined with lubricating oil. However, it is unclear how textured surfaces affect the friction behavior of a-C at atomic scale, specifically the transformation of interfacial structure and the flow of lubricating oil, owing to the limitations of experimental characterization. Here, a-C films with different textured surfaces were fabricated, and the friction behaviors of mating a-C surfaces with textured parameters, including nanoscale depth and width, were examined by reactive molecular dynamics simulation. Results indicate that compared to that under dry condition, the introduction of a textured surface reduces the friction coefficient of a-C under oil lubrication condition. However, its efficiency highly depends on the depth and width of textured surface, exhibiting different effects on hydrodynamic lubrication. The increase in textured depth causes the friction coefficient decreased first and then increased, attributing to the lubrication from hydrodynamic to boundary state as primary mechanism. The regional aggregation of lubricant atoms with a textured width on the a-C surface occurs at the friction interface following the increased friction coefficient. These results provide insights into the underlying friction mechanism of a-C films induced by surface texturing and enable the development of highly efficient lubrication systems for applications.