Vitreous bond silicon carbide wheel for grinding of silicon nitride

This study investigates the grinding of sintered silicon nitride using a SiC wheel with a fine abrasive grit size and dense vitreous bond. The difference of hardness between the green SiC abrasive and sintered Si₃N₄ workpiece (25.5 vs. 13.7 GPa) is small. Large grinding forces, particularly the specific tangential grinding forces, are observed in SiC grinding of Si₃N₄. The measured specific grinding energy is high, 400–6000 J/mm³, and follows an inverse relationship relative to the maximum uncut chip thickness as observed in other grinding studies. The SiC wheel wears fast in grinding Si₃N₄. The G-ratio varies from 2 to 12. Two unique features in SiC grinding of Si₃N₄ are the trend of increasing G-ratio at higher material removal rate and the excellent surface integrity, with 0.04–0.1 μm R_a and no visible surface damage. For a specific material removal rate, surface cracks along the grinding direction are generated on the ground surface. The problem of chatter vibration was identified at high material removal rates. Periodic and uneven wheel loading marks and clusters of workpiece surface cracks across the grinding direction could be observed at high material removal rates. This study demonstrates that the SiC grinding wheel can be utilized for precision form grinding of Si₃N₄ to achieve good surface integrity under a limited material removal rate.