The wear mechanisms of diamond grits in grinding of alumina and yttria-stabilized zirconia under different cooling-lubrication schemes

Abstract

Abrasion is the primary wear mechanism of diamond grits during grinding of advanced ceramics. This work not only highlights some unreported modes of wear of diamond grits but also illustrates and describes their mechanisms while grinding two dissimilar advanced ceramics, viz. alumina and yttria-stabilized zirconia (YSZ). Long-cycle plunge grinding of the ceramics was conducted with single-layer electroplated diamond wheels at 30 m/s and 50 m/s grinding speeds under three different cooling-lubrication schemes – flood cooling (FC), MQL-soluble oil (MQL-SO) and MQL-neat oil (MQL-NO). Radial wheel wear was measured employing indirect profilometry. Diamond grits on the electroplated wheels were observed under SEM before and after grinding to identify and characterize various modes of wear. Severe wheel loading was observed while grinding alumina and YSZ under FC and MQL-SO. Indentation fatigue fracture was found to be the dominant mode of diamond grit wear during alumina grinding under wheel loading conditions. The wear of diamond grits during YSZ grinding was dominated by thermal fatigue fracture at a higher grinding speed of 50 m/s. Thermal degradation of diamond grits was examined with Raman spectroscopy which revealed graphitization of some of the active diamond grits after YSZ grinding under FC and MQL-NO at 50 m/s.