Atomic Degradation and Wear of Thin Carbon Films Under High-Speed Sliding Contact Using Molecular Dynamics Simulation

Abstract

The thermomechanical contact behavior and the resulting change in atomic structure of diamond-like carbon (DLC) film were investigated through molecular dynamics simulation. Under the high-speed sliding contact between a diamond asperity and an amorphous DLC film, the atomic stress, temperature rise, and atom coordination number were measured with the elapsed contact time. It was observed that the increase in atomic stress caused higher kinetic energy on the carbon atoms, which accordingly led to the increase in the DLC film temperature. Examining the change in atom coordination number for the carbon atoms in the DLC film, it could be found that the number of sp 2 bonds (i.e., three-fold structure) increased with the contact time, which supported the graphitization process on the DLC film. During the sliding contact, some of the carbon atoms were debonded from the diamond asperity, which were rebonded (or transferred) onto the DLC film surface right after. From the analysis of atomic structural change, it could be concluded that this rebonding process was relying on covalent bonding rather than van der Waals interaction.