Cyclic deformation fatigue behaviour of Ti6Al4V thermochemically nitrided for articular prostheses

Titanium and its alloys have many attractive properties including high specific strength, low density, and excellent corrosion resistance. Titanium and the Ti6Al4V alloy have long been recognized as materials with high biocompatibility. These properties have led to the use of these materials in biomedical applications. Despite these advantages, the lack of good wear resistance makes the use of titanium and Ti6Al4V difficult in some biomedical applications, for example, articulating components of prostheses. To overcome this limitation, nitriding has been investigated as a surface-hardening method for titanium. Although nitriding greatly improves the wear resistance, this method reduces the fatigue strength. Low cycle fatigue performance in air of nitrided Ti6Al4V at different deformation amplitudes has been studied. Results show a reduction of low cycle fatigue life of up to 10% compared to the non-treated material. Studies suggest it is not related to the titanium nitride surface layer, but to microstructural changes caused by the high temperature treatment. (Journal of Applied Biomaterial & Biomechanics 2003; 1: 43-7).