Influence of grain size on fatigue strength of nitrided pure Ti

Metallurgical factors controlling the fatigue properties of gas-nitrided titanium have been studied through some critical experiments concerning the fatigue strength of nitrided pure titanium whose grain size had been changed from 100 μm to 2 800 μm through annealing prior to nitriding. The results are summarized as follows. (1) There exists a Hall-Petch-types relationships between the fatigue strength of nitrided pure titanium and its grain size. (2) The fatigue strength of pure titanium is improved by low-temperature nitriding (620°C) where the grain growth can be suppressed. (3) The fatigue strength of nitrided pure titanium decreases with increasing the thickness of compound layer at the specimen surface.