Investigation of the tribological behaviors for 4H–SiC substrate under different lubrication conditions

Lubrication conditions are an important factor affecting both the machining efficiency and quality of 4H–SiC. To investigate the tribological behaviors under different lubrication conditions, a series of scratching experiments are conducted under different loads and environments. The X-ray photoelectron spectroscopy (XPS) surveys and atomistic simulations are used to explain the different tribological behaviors. Both experimental and simulation results show that liquid lubrication can significantly reduce the coefficient of friction (COF) and minimize structural damage. Compared to pure water, the H₂O₂ solution is more conducive to the oxidation of SiC atoms and the modification of tribological behaviors. However, the difference in tribological behaviors between H₂O₂ solution and pure water diminishes as the load increases. The XPS surveys show that the liquids lead to higher-order oxidized species of SiC atoms, such as Si₄C_4-xO₂ and Si-O_x-C_y, which are also observed in the simulation results. It is shown that the oxidized species can reduce the direct bonding between SiC and diamond indenter, which is an important reason for the lower COFs in the liquids. Since the liquids can reduce the direct bonding and mechanical interaction between 4H–SiC and diamond, the material removal rate is much lower under lubrication conditions.