Effect of Hydrogen on Fatigue Life and Fracture Morphologies of TRIP-Aided Martensitic Steels with Added Nitrogen

• Published in: Metals (Basel ) Vol. 14; no. 3; p. 346
• Main Authors: Hojo, Tomohiko, Nagasaka, Akihiko, Kobayashi, Junya, Shibayama, Yuki, Akiyama, Eiji
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.03.2024
• Subjects: AlN; Aluminum compounds; Carbon; Cleavage; Corrosion resistance; Crack initiation; Crack propagation; Dimpling; Elongation; Fatigue; Fatigue cracks; Fatigue failure; Fatigue life; fatigue properties; Fatigue testing machines; Fracture mechanics; Fracture surfaces; Heat treating; High strength steel; Hydrogen; hydrogen embrittlement; Martensitic stainless steels; martensitic steel; Materials; Metal fatigue; Morphology; Nitrogen; Precipitates; Propagation; Radiation; Scanning electron microscopy; Stainless steel; Stress concentration; Tensile properties; Tensile strength; transformation-induced plasticity; Japan
• ISSN: 2075-4701; 2075-4701
• DOI: 10.3390/met14030346

The effects of hydrogen on the tensile properties, fatigue life, and tensile and fatigue fracture morphologies of nitrogen-added ultrahigh-strength transformation-induced plasticity (TRIP)-aided martensitic (TM) steels were investigated. The total elongation and number of cycles to failure (Nf) of the hydrogen-charged TM steels decreased with the addition of nitrogen; in particular, adding 100 ppm of nitrogen decreased the total elongation and Nf of the TM steels. The quasi-cleavage cracking around the AlN occurred near the sample surface, which is the crack propagation region, although dimples appeared at the center of the fracture surface in the tensile samples. The initial fatigue crack initiated at the AlN precipitate or matrix/AlN interface, located at the notch root. During crack propagation, new cracks were initiated at the AlN precipitates or matrix/AlN interfaces, while quasi-cleavage crack regions were observed around the AlN precipitates. The decrease in the total elongation and Nf of the hydrogen-charged TM steel with 100 ppm of added nitrogen might be attributable to the crack initiation around the AlN precipitates formed by a large amount of hydrogen trapped at the AlN precipitates and matrix/AlN interfaces, and to the dense distribution of AlN, which promoted crack linkage.