Abstract
We present a quantitative evaluation of abrasive grit size dependency of subsurface damages on Zerodur glass-ceramic substrates induced by precision grinding. The depths of subsurface damages are evaluated for the metal-bonded grinding cup tools with four different grit sizes, D126, D64, D35, and D15, for the fixed nominal grinding process parameters. The micro-crack depth is driven by the mechanism between the abrasive grit and brittle glass, which generates median or radial cracks through the bulk material. The initiation and propagation of subsurface damages beneath the brittle glass-ceramic substrate of Zerodur are explored by the cross-sectional polishing method, which takes advantage of the optical contact bonding method without any adhesive, and are imaged by scanning electron microscopy. A novel hybrid methodology, which comprises both destructive and non-destructive subsurface evaluation tools, is developed and employed for evaluating the micro-cracks quantitively. The procedure is based on a repetitive and consecutive chemical acid etching after the surface is grounded, flat substrate polishing with a conventional polishing machine, a white light interferometer, and an image analysis. The four grit sizes, D126, D64, D35, and D15, correspond to the rough cut through to the complete precision grinding’s fine cut. The subsurface damages are measured to be 71 µm, 35 µm, 25 µm, and 7 µm from rough to fine grit sizes. The results are consistent with the theoretical model and previous work.