Sensitivity of Scratch Resistance to Grinding-Induced Damage Anisotropy in Silicon Nitride

Single-grit scratch experiments were conducted on polished as well as on longitudinally and transversely ground silicon nitride specimens to investigate the influence of grinding direction on scratch resistance. It was found that the volume of material removed and the extent of cracking were the largest when the scratches were parallel to the grinding direction and were the least on the polished specimens. These results were rationalized based on the grinding-induced sub-surface damage anisotropy and were quantified using a scratch resistance measure. A linear elastic fracture mechanics analysis revealed that only cracks of certain length and orientation grow to cause the observed trends in the scratch resistance.