Atomic scale investigation of notch evolution on 4H-SiC under different cutting surfaces and environments

Due to the hardness and brittleness of silicon carbide, the surface defects of 4H-SiC are easily transferred to the machining stage. To better illustrate the influence of pre-existing notch on cutting process, the notch evolution on 4H-SiC under different cutting surfaces and environments is studied by molecular dynamics simulation. It is found that 0001 face 12¯10 basal slip is one of the most common slip systems of 4H-SiC and the basal slip is easy to start from the tip of notch. Water film can promote the evolution of notch and lead to deeper defective structures. When there is no water film, the notch will be filled with phase transformation atoms. Since the defects tend to generate and propagate along the basal plane of 4H-SiC, the subsurface damage caused by 011¯0 face cutting is much deeper. When cutting on 0001 surface, there will be massive spalling which can lead to a sharp increase in chip atoms. Thus, cutting on 0001 surface can not only reduce the depth of subsurface damage but also improve material removal rate. In addition, the basal slip is usually accompanied by long dislocation lines and more dislocation lines will be left when cutting on 011¯0 surface.