Simple Technique for Observing Subsurface Damage in Machining of Ceramics

A simple technique is proposed for directly observing subsurface damage in the machining of ceramics. The technique requires two polished specimens and an optical microscope with Nomarski illumination for examination. The subsurface damage created by the grinding of an alumina ceramic is investigated using this technique. The mode of damage is identified as intragrain twinning/slip, and intergranular and transgranular cracking. Chipping along the twinned planes and along the transgranular crack planes, and dislodgement of the intergranularly debonded grains are suggested to be the mechanisms of material removal in the machining of this alumina ceramic.