The closure of indentation cracks and strength recovery by low temperature ageing in Y-TZP

Abstract

This paper reports that the microstructure-mechanical property relationships in yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) have been well established in the advanced ceramic community. These highly toughened ceramic materials suffer, unfortunately, a thermal instability when they are subjected to a hydrothermal environment at temperatures in the range of 100 to 400[degrees]C, due to the tetragonal to monoclinic transformation occurring on the aged surface. It has been observed that a Y-TZP will be completely disintegrated on ageing at the low temperatures for a long enough period. On the other hand, surface toughening is obtainable when the Y-TZP is thermally treated at the low temperatures in a controlled manner, as a result of the development of compressive stresses on the aged surface. Structural ceramic materials are very sensitive to microstructural defects, which include both the processing-related flaws and the structural damage caused during the period of application. Catastrophic failure of ceramic materials is a consequence of fast crack propagation under loading conditions. It is therefore essential to control both the number and sizes of microstructural defects present in an advanced ceramic material in order to improve its engineering reliability. For many engineering applications, such as those in chemical engineering industries, Y-TZP ceramics aremore » often subjected to a combination of mechanical and hydrothermal environments. Apparently, the presence of any microstructural defects such as cracks and pores may have a large impact on the response of Y-TZP to these mechanical and hydrothermal conditions. The aim of the present work is to investigate the effects of a hydrothermal environment on the post-indentation cracks in a 3 mol% yttria stabilized tetragonal zirconia polycrystals.« less