Spark plasma sintered 3Y-TZP has been investigated with respect to hydrothermal ageing and grinding. The sintering was performed between the temperatures of 1,100 and 1,600 °C for a soaking time of 5 minutes and the resulting materials were obtained with grain sizes between 65 to 800 nm and relative densities between 88.5 to 98.8%. Experiments on hydrothermal ageing in water vapour at 131 °C, 2 bars during 60 hours shows that phase stability is retained, elastic modulus and hardness of near surface region measured by nanoindentation does not change in fine grain (<200 nm) materials, in spite of porosity. In ground specimens, very small amount of transformation was found for all grain sizes studied.

No abstract

Study of near surface changes in yttria-doped tetragonal zirconia after low temperature degradation Full tetragonal 3 mol.% Y 2 O 3 doped zirconia has been subjected to hydrothermal ageing in water at 131 8C in order to study the change in microstructure just below the surface. The degraded layer was examined by scanning and transmission electron microscopy in a section perpendicular to the surface which was prepared by focus ion beam machining. The existence of microcracks and transformed grains in a thin surface layer of the hydrothermal degraded specimens is shown. Scratch damage in annealed and in thermally degraded specimens is compared.

Effect of low-temperature degradation of 3Y-TZP ceramics (polycrystalline zirconia stabilized by 3mol% of yttria) on contact damage resistance has been studied applying scratch testing technique. Friction properties and damage mechanisms have been investigated for various degrees of hydrothermal ageing, i.e. for different grain sizes and crystallography, and for different thickness of the degraded surface layer. The onset of plastic damage, catastrophically cracking, grain pull-out, spalling and chipping due to top layer debonding have been identified. The contact damage micromechanisms corresponding to various degrees of degradation have been studied in detail by interferometry and microscopy.