Molecular simulation of ultrasonic assisted diamond grit scratching 4H-SiC single-crystal

Single-crystal silicon carbide (SiC), which has strong chemical inertness and high brittleness, poses a major challenge for the ultra-precision machining of its substrate. Compared to chemical-mechanical polishing, ultrasonic vibration-assisted polishing has obvious advantages, but the removal mechanism remains unclear. In this study, the single grit diamond scratching process of 4 H-SiC was investigated with and without ultrasonic vibration using molecular dynamics. The effects of different amplitudes and frequencies on the friction force, temperature, atomic removal number, surface morphology, crystal structure, stress, and dislocation were assessed, and the formation process of dislocation was revealed. The simulation results showed that the friction force decreased with increasing amplitude and frequency, whereas the influence of temperature was reversed. This amplitude is beneficial for increasing the number of atoms removed. The relationships among the stress, dislocation, amplitude, and frequency are complex. The angle of the principal stress changes with stress, which is also a key factor in the lateral and longitudinal propagation of dislocations. The stress distribution was determined based on amplitude and frequency. The results proved that a single grit with ultrasonic vibrations has better removal efficiency and processing quality, provided that the vibration parameters are appropriately matched.