Investigation on surface/subsurface damage mechanism in yttrium aluminum garnet crystal lapping and polishing

The surface/subsurface damage of yttrium aluminum garnet (YAG) crystal is inevitable in lapping and polishing. The effects of fixedabrasive lapping and polishing on the surface topography, surface/subsurface damage characteristics and material removal mechanism of YAG crystal are investigated. The experimental results show that the material is in brittle removal mode when the surface is lapped by fix abrasive and polished by 7μm and 5μm alumina, while the material is in ductile removal mode when the surface is polished by 2.5μm, 0.3μm alumina and silica sol. In the brittle removal mode, obvious pits and scratches are on the surface and the subsurface damage is serious. But in the ductile removal mode, the surface is smooth and the subsurface damage is shallow.