Spherical and Vickers Indentation Damage in Yttria‐Stabilized Tetragonal Zirconia Polycrystals

Abstract

Damage induced in an yttria‐stabilized tetragonal zirconia polycrystal by spherical and Vickers indentations was investigated. Scanning acoustic microscopy revealed that, as indentation stress increased, the spherical indentation gradually developed subsurface damage, until it experienced a transition to a fully plastic state, characterized by a highly anisotropic variation in the leaky Rayleigh wave velocity, vR, and very similar to that for Vickers indentation. The transition was a result of the formation of a microcracked core beneath the contact. Indenter geometry had an appreciable effect only within the core; the distribution of microcracks differed depending on the indenter used, as confirmed by direct observations using a scanning electron microscope. In contrast, the residual stresses in the elastic‐plastic zone were insensitive to indenter geometry. The resulting plastic zone was not hemispherical but rather cylindrical, irrespective of indenter geometry.