Improvement of fatigue properties of Ti-6Al-4V alloy under four-point bending by low temperature nitriding

•A nitrogen compound layer is formed on the surface of Ti-6Al-4V nitrided at 873 K.•Nitrogen diffusion is observed on the surface of Ti-6Al-4V nitrided at 823 K.•Low temperature nitriding suppresses the grain-coarsening of Ti-6Al-4V.•Low temperature nitriding at 823 K increases the fatigue limit of...

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Bibliographic Details
Published in:International journal of fatigue 2019-03, Vol.120, p.134-140
Main Authors: Kikuchi, Shoichi, Yoshida, Sho, Ueno, Akira
Format: Article
Language:English
Subjects:
Bending fatigue
Coarsening
Fatigue
Fatigue limit
Fatigue tests
Fractography
Fracture mechanics
Heat treating
Low temperature
Materials fatigue
Nitriding
Nitrogen
Nitrogen compounds
Stress ratio
Titanium alloy
Titanium alloys
Titanium base alloys
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Summary:•A nitrogen compound layer is formed on the surface of Ti-6Al-4V nitrided at 873 K.•Nitrogen diffusion is observed on the surface of Ti-6Al-4V nitrided at 823 K.•Low temperature nitriding suppresses the grain-coarsening of Ti-6Al-4V.•Low temperature nitriding at 823 K increases the fatigue limit of Ti-6Al-4V. Low temperature nitriding (LTN) was performed for titanium alloy (Ti-6Al-4V) to improve its fatigue properties. A nitrogen compound layer was formed on the surface nitrided at temperatures higher than 873 K, whereas nitrogen diffusion was observed on the surface nitrided at 823 K. Fatigue tests were performed by four-point bending in air under a stress ratio of 0.1. The fatigue limit for Ti-6Al-4V tended to increase with a decrease in the nitriding temperature. LTN at 823 K increased the fatigue limit of Ti-6Al-4V due to the formation of the surface with no nitrogen compound layer and suppression of grain-coarsening.
ISSN:0142-1123
1879-3452
DOI:10.1016/j.ijfatigue.2018.11.005