Wear process of single crystal diamond affected by sliding velocity and contact pressure in mechanical polishing

• Only two wear periods are observed in diamond polishing, and the first stage can be shortened.
• A diamond carbon amorphization dependent model is established to calculate the wear rate.
• Effect laws of sliding velocity and contact pressure are different on the wear rate.

In this work, the influences of sliding velocity and contact pressure on the wear rate of diamond substrate in mechanical polishing are investigated experimentally and theoretically. The experimental observations indicate that the wearing process only consists of the wear-in and stable wear periods. The removal thickness of diamond crystal first increases nonlinearly in the wear-in stage, but then linearly in the subsequent stable wear stage. A diamond carbon amorphization-dependent model is established to calculate the linear variations of removal thickness, which gives a satisfactory prediction accuracy as compared to the experimental data. Although the experiment results demonstrate that the higher sliding velocity or contact pressure will cause a higher wear rate of diamond substrate, the action laws are thoroughly different according to the theoretical prediction. A greater sliding velocity increases the amorphization rate of diamond carbons and the scratching frequency of diamond grits. However, a higher contact pressure produces a larger contact area, which forces more diamond grits to scratch on the surface of diamond substrate.