Mechanism for material removal in diamond turning of reaction-bonded silicon carbide

Reaction-bonded silicon carbide (RB-SiC) is a new ceramic material that has extremely high strength and hardness. Diamond turning experiments were performed on RB-SiC to investigate the microscopic material removal mechanism. Diamond tools with large nose radii of 10 mm were used for machining. It was found that the surface roughness was not significantly affected by the tool feed rate, but was strongly dependent on the tool rake angle. The mechanism for material removal involved plastic deformation, microfracture and dislodgement of 6H-SiC grains. Raman spectroscopy revealed that the silicon bond component underwent amorphization, while no phase transformation of 6H-SiC grains was observed. Tool wear was also investigated and two types of wear patterns were identified. Under the experimental conditions used, a surface finish of 23 nm Ra was obtained even at an extremely high tool feed rate of 72 μm/rev. This study demonstrates the feasibility of precision machining of RB-SiC by diamond turning at a very high material removal rate.