Corrosion fatigue of bio-ceramic sapphire in isotonic sodium chloride solution

Alumina (sapphire) is considered as a candidate material for bio-ceramics, because of its superior strength characteristics, corrosion resistance and bio-inert properties. These biomaterials are used in aggressive corrosive e nvironments such as the human body under severe mechanical conditions super posing cyclic loading on constant load. Therefore, it is necessary to evalu ate the static and cyclic fatigue characteristics in an environment as seve re as the human body. In this paper, the effects of human body environment corrosion upon cyclic fatigue characteristics of single crystal sapphire an d polycrystalline alumina have been investigated using in vitro testing in isotonic sodium chloride solution, whose composition is closely similar to body fluid. Also, degraded corrosion morphologies and fracture surfaces of single crystal sapphire specimens were examined in derail by SEM and AFM. T he fatigue limit of single crystal sapphire was found to be extremely degra ded in the isotonic sodium chloride solution compared with that in air. The importance of environment assisted slip deformation is indicated. (C) 2000 Elsevier Science Ltd. All rights reserved.