Nanoindentation characterization of the elasticity, plasticity and machinability of zirconia

Abstract

Zirconia has the loading rate-dependent nanoindentation contact hardness which is a hybrid property encompassing both the elastic and plastic behaviors which affect its machinability, wear and fatigue properties. This work aimed to partition the deformation behavior into the elasticity and plasticity, and to predict the machinability of zirconia at different nanoindentation loading rates using the Sakai and the Sakai–Nowak models. The results reveal that the resistance to plasticity of zirconia was loading-rate independent (ANOVA, p>0.05). The plastic displacement showed the loading-rate dependent character following a power law while the elastic displacement revealed approximately a loading-rate independent constant. The elastic and plastic deformation components demonstrated loading-rate dependence in which at the low loading rates the two components approximately coincided but at high loading rates, the elastic deformation component was slightly dominant. Zirconia also showed higher ductility than its elasticity indices at higher loading rates. The loading-rate independent resistance to machining-induced cracking of zirconia was lower than its pre-sintered state. This study lends credence to the realization of a small-volume material removal for crack-free zirconia surface generation at high deformation rates for zirconia in abrasive machining.