Molecular dynamics simulation of silicon carbide nanoscale material removal behavior

The scratching processes of monocrystalline and polycrystalline silicon carbide (SiC) with diamond grit were studied by molecular dynamics simulation to investigate the nanoscale material removal behavior. The results showed that, for both monocrystalline and polycrystalline SiC, the material removal processes were achieved by the phase transition to the amorphous structure. Large depth of cut and low scratching speed induced the large scratching forces, stress, and surface damage layer thickness. Less amorphous structure phase transition, smaller normal scratching force, and higher tangential stress were found in polycrystalline SiC, comparing to the monocrystalline SiC, due to the material soften caused by the microstructure, under all scratching conditions. Furthermore, the tangential stress showed highly dependent on the grain geometry and grain boundary (GB) location in polycrystalline. The subsurface damage layer in polycrystalline was little thinner than that in monocrystalline before the new GB generation at a low depth of cut and deteriorated at large depth of cut. In addition to the plastic deformation, which occurred in the monocrystalline SiC nanoscale scratching, the intergranular fracture and transgranular fracture were also observed through the GB generation and connection in polycrystalline SiC.