Molecular dynamics study of the effect of water lubrication three-body polishing sapphire

Sapphire is widely used owing to its superior mechanical, physical, and chemical properties. However, the removal mechanism of sapphire in chemical mechanical polishing (CMP) is not yet fully understood. This study investigated the polishing mechanism of rolling abrasive grains in sapphire under water lubrication and employed molecular dynamics (MD) to simulate the polishing process under different abrasive grain sizes and polishing velocities. The abrasive chips, energy, polishing force, and dislocation motion were analyzed to determine the deformation damage mechanism of sapphire during polishing. The results indicated that the material removal rate and surface roughness reached their maximum critical values with increased abrasive grain size. Moreover, the highest surface roughness and atom removal rate were achieved when the abrasive grain radius was 30 A. With variations of the polishing velocity, more atoms were retained in the workpiece when the tangential speed was smaller than the abrasive grain rotation velocity, resulting in better surface quality. These findings provide a theoretical foundation for sapphire polishing.