Ageing effects on the nanoindentation response of sub-micrometric 3Y-TZP ceramics

The surface mechanical response, specifically hardness and Young's modulus, of two thermally aged 3Y-TZP ceramics with different grain size was evaluated by depth-sensing indentation tests. The ageing treatment were carried out in autoclave at 121°C with a water vapor pressure of 0.235 MPa for different times. The depth-sensing indentation tests were carried out using a Berkovich diamond tip on a commercial nanoindenter. The presence of microcracking in the transformed layer have been formulated only on the basis of the nanoindentation outcomes. The surface mechanical behavior of aged zirconia ceramics was influenced, at different sampling depths, by ageing time and mean grain size. Ageing treatment have been shown to replicate the transformation effects observed in retrieved prostheses and the assessment of the surface mechanical behavior gives useful information about the wear and contact properties of these aged ceramics.