Hydrothermal ageing of smooth and cracked 3Y-TZP

Abstract

The effect of hydrothermal degradation on the flexural strength of smooth and indented specimens of tetragonal polycrystalline zirconia doped with 3% mol yttria (3Y-TZP) has been investigated. The specimens were exposed for several periods of time to water vapour at 131 ºC in autoclave. The t-m transformation was studied by micro-Raman spectroscopy and SEM on the specimen’s surface and on Palmqvist crack faces after fracture. It is shown here that the Weibull modulus of the flexure strength of smooth degraded specimens increases, while the flexural strength decreases in the ageing interval studied. On the contrary, specimens with indentation cracks larger than the size of crack-like natural defects, increase strongly their flexural strength after an incubation ageing time. It is shown here that the Weibull modulus of the flexure strength of smooth degraded specimens increases, while the flexural strength decreases in the ageing interval studied. On the contrary, specimens with indentation cracks larger than the size of crack-like natural defects, increase strongly their flexural strength after an incubation ageing time. It is proposed that crack tip blunting by water vapour is responsible for this effect, which has not been previously reported. It is also shown that exposure to water vapour can be an excellent tool to reveal cracks in 3Y-TZP.