EFFECTS OF LIQUID ENVIRONMENTS ON ZIRCONIA-TOUGHENED ALUMINA .2. MECHANICAL-PROPERTIES

The corrosion resistance of a zirconia-toughened alumina after prolonged exposure to a series of liquid environments is assessed. From the range of environments studied, only HCl caused a significant degradation in both strength and toughness. The mechanism of this deleterious behaviour was the transformation of the tetragonal zirconia particles to the monoclinic polymorph at the surface. The mechanical properties were determined by both the monoclinic content and the depth of penetration of the HCl, and hence the depth of the monoclinic-containing surface layer, with the latter probably being more important.