High speed moderate depth grinding of alumina and yittria stabilized zirconia

Abstract

Material removal in low speed ceramic grinding is primarily due to micro-brittle fracture. High speed grinding of ceramics reduces micro-brittle fracture, but the main challenge to restrict the surface and sub-surface damage remains intact. In this work, alumina and yittria stabilized zirconia (YSZ) were ground using single layer electroplated diamond grinding wheels at wheel speed up to 200 m/s under conventional flood cooling environment. Wheel downfeed and work speed were kept constant. Grinding forces were monitored, morphology of the ground surfaces was investigated and surface roughness was measured across and along grinding directions. Surface residual stresses were measured using sin2ψ method of X-ray diffraction. Results indicated that micro-brittle fracture got substantially reduced at high wheel speed. A transition from brittle fracture to ductile flow was observed for alumina as the wheel speed was increased beyond 120 m/s. The ratio of average surface roughness values across and along the grinding directions was in good agreement with morphological observations. High wheel speed reduced grain fracture and surface crack density for alumina and YSZ, respectively. Compressive residual stresses were generated for alumina and YSZ, and were found to be in good correlation with normal grinding force. Overall, high speed grinding yielded better surface characteristics.