Surface Integrity of Quartz Glass Induced by Ultra-precision Grinding

Abstract

In order to achieve high efficiency and low damage grinding for quartz glass, surface and subsurface qualities of ground quartz glasses using diamond wheels of various grit sizes are systematically investigated, and a mathematic relationship between the surface roughness and the subsurface damage depth is established. Grinding performance and surface integrity of quartz glass under diamond grinding using grit size of 400#, 1 500 #, 2 000# and 5 000#, respectively, are characterized in terms of surface topography, surface roughness and subsurface defect depth. The material removal mode of quartz glass for such diamond wheels is presented as well. The mechanism of surface morphology and subsurface microcrack produced in brittle removal mode is analyzed using indentation fracture mechanics, and the relationship between roughness value PV and subsurface damage depth SSD is established. The experiment results showed that with the decrease in wheel grit size, the quality of defects including pits, microcracks and deep scratches generated on the surface decreased, resulting in the decreased surface roughness and subsurface damage depth from Ra 274.0 nm, PV 5.35 μm and SSD 5.73 μm for 400# wheel to Ra 1.4 nm, PV 0.02 μm and SSD 0.004 μm for 5 000# wheel. The dominant removal mode in grinding quartz glass for 400# and 1 500# wheel is brittle fracture, that for 2 000# wheel included both brittle fracture and ductile cutting but ductile removal is more prevalent, and that for 5 000# wheel is ductile cutting removal. In the brittle mode grinding process, the relationship between subsurface roughness value PV and subsurface damage depth SSD is in accord with the formula SSD=(0.627~1.356) PV4/3.