Toughening vs. Environmental aging in BIOLOX® delta: A micromechanics study

Abstract

A BIOLOX® delta femoral head has been evaluated with respect to its surface micromechanical behavior and its environmental aging response upon increasing elongation time in a hot water vapor environment. A microscopic evaluation of surface phenomena was obtained according to confocal Raman microprobe spectroscopy. The confocal configuration of the optical probe allowed spectroscopic assessments in the very neighborhood of the material surface. After extreme exposure time in moist environment, a portion of zirconia dispersoids transformed from the tetragonal to the monoclinic polymorph on the surface of the sample. A pyramidal diamond indentation technique was applied in order to analyze crack initiation. A significant influence of the transformation to the crack tip opening was observed. However, it should be noted that such an effect is likely to occur only after extremely long exposure in hot vapor environment.