Fatigue strength of nitrided high-strength titanium alloy

This study is conducted to clarify the relationship between the fatigue strength of nitrided titanium and that of the substrate. The result shows that the fatigue strength of nitrided pure titanium is improved by the increase in the fatigue strength of its substrate. It can be considered that this improvement is caused by the reduction in the magnitude of the stress field which is generated in the compound-layer by the slip of the substrate. However, the above improvement is limited in case of nitrided titanium alloys which have high strength such as nitrided Ti-6 Al-4 V and SP-700 alloys. That is because the compound-layer is subjected to the additional intensive tensile stress induced by the difference of Young's moduli between the layer and the substrate.