Wear and friction between smooth or rough diamond-like carbon films and diamond tips

The tribology of diamond-like carbon (DLC) films has been studied for decades, but their friction and wear mechanisms at the nanoscale still remain unclear due to experimental limitations. To address this challenge, the friction and wear between DLC films and diamond tips are investigated via molecular dynamics simulations. It is found that the load can increase wear rate of the DLC film by inducing transition of its wear from adhesive to abrasive type. The calculated friction force follows the prediction of the Bowden-Tabor model at relatively small loads but deviates at large loads due to the formation of transfer layers. The high velocity can decrease the friction force and wear rate of the DLC film by reducing the sliding depth of the diamond tip and number of bonds at the contact interface. When the surface roughness of the DLC film increases, its abrasive wear is highly promoted, leading to the fact that the friction force increases while the wear rate initially decreases and then increases. This surface roughness-dependent wear behavior is attributed to the competition between the adhesive and abrasive wear.