Investigation on the surface topography and surface/subsurface damage mechanisms of polycrystalline yttrium aluminum garnet ceramics in ultra-precision grinding

Abstract

This study investigates the surface topography and surface/subsurface damage mechanisms of polycrystalline yttrium aluminum garnet (YAG) ceramics in ultra-precision grinding. Firstly, the impacts of grinding parameters on the depth of subsurface damage was studied using the cross-sectional polishing method. Secondly, focused ion beam (FIB) thinning and transmission electron microscopy (TEM) were applied to observe the subsurface damage of YAG ceramics in ultra-precision grinding. Finally, the effect of process arguments on the formation of subsurface damage of polycrystalline YAG ceramics in ultra-precision grinding was analyzed. The results indicate that process parameters significantly affect the surface/subsurface damage defects of YAG ceramics during ultra-precision grinding. The degree of effect follows the order: grinding depth (a_p) > feed rate (F) > diamond wheel speed (n_s) > workpiece speed (n_w). The surface roughness increases with the increase of workpiece speed, feed speed and grinding depth, but the increase of grinding depth will lead to a steep increase in surface roughness, and the surface roughness under different parameters is positively correlated with the surface defects. The all-plastic ultra-precision grinding surface of YAG ceramics with a roughness of 6 nm can be achieved with the resin bonded D7 diamond grinding wheel under the process parameters of the grinding speed is 7000 rpm, the workpiece speed is 60 rpm, the grinding depth is 0.5 μm, and the feed speed is 1.5 mm/min. The subsurface damage depth of YAG ultra-precision grinding is less affected by workpiece speed, and increases linearly with the increase of feed speed and wheel speed, and increases sharply with the increase of grinding depth. The transition from crystal to amorphous occurs in the grain, including atomic scale defects such as dislocation, layer fault and lattice distortion, which is the fundamental cause of subsurface microscopic damage.