The Effects of Annealing on Surface Machining Damage of Alumina Ceramics

Abstract

The grinding process induces residual stresses and scratch cracks near the surfaces of ceramic work-pieces. In order to reduce the influences of the surface damage layers, the effects of annealing on the bending strength of alumina specimens ground with a #170 diamond wheel were investigated. Surface residual stresses were measured by the X-ray diffraction method and the effects of residual surface stresses on the bending strength were discussed using a simplified model. As a result, the annealing process restored the surfaces damage layers and bending strengths of ground alumina specimens to the initial condition. The compressive residual stress influenced the micro-cracks perpendicular to the grinding direction and consequently the bending strengths increased slightly, however, they hardly influenced the deep scratch cracks parallel to the grinding direction.