Analysis of surface and subsurface damage of micro-ground Bk7 glass using on machine fabricated PCD micro-tool

This paper presents the research results of the morphology of subsurface damage (SSD) in BK7 glass ground with on-machine fabricated PCD micro tool. Grinding generated damages during this process are assessed and characterized using bonding interface sectioning technique combined with field emission scanning electron microscopy (FESEM). Both the damage depth and surface roughness are found to be influenced by the depth of cut, and spindle speed. In addition to this, two major type of grinding damage have been identified likely chipping damage and micro-cracking damage. Lateral, median and cone cracks are found to be existed in the sub-surface. As long as the cutting points are unloaded and residue can escape; the material is removed in a combined brittle and ductile mode. When the cutting surface is loaded with residue, the tool work piece interface temperature becomes so high that the material is removed by plastic flow. Hence the surface is polished with fine debris. Unfortunately, as this surface cools down, thermal quenching produces a network of crack. Although the machined surface seems to be show ductile mode of cutting behaviour even at higher material removal, analysis of subsurface damage shows that the material removal is a combined effect of grain dislodgement, micro-cracking and plastic deformation. These results provide valuable insight into the grinding damage induced due to the properties of glass as well as process parameters.