Strength and grinding residual stresses of Y-TZP with duplex microstructures

The influence of grinding surface stresses on the strength and apparent fracture toughness of Y-TZP doped with 2.8% molar Yttria has been analysed. It is shown that by means of heat treatments of 2.8Y-TZP at 1650 °C for different times, a duplex cubic-tetragonal microstructure can be produced, which is more transformable and tougher than the starting 2.8Y-TZP. The effect of grinding is studied in samples heat-treated under different conditions and it is shown that compression residual stresses are induced in a surface layer. These are estimated by X-ray diffraction and by measuring the length of indentation cracks in ground and in annealed specimens. The effect of residual stresses on strength and fracture toughness is discussed in terms of a simple model based on a uniform compression residual stress in a surface layer.