Revealing grain refinement and hydrogen trapping mechanism for anti-hydrogen susceptibility of Nb-alloyed 34MnB5 press hardened steel

• Published in: International journal of hydrogen energy Vol. 92; pp. 283 - 299
• Main Authors: Jamal, Saeed, Wang, Yangwei, Shehzadi, Fatima, Abro, Irfan Ali, Wang, Jian, Gui, Lintao, Zhao, Yan, Lu, Hongzhou, Bhatti, Tahir Mehmood, Baig, Mirza Muhammad Abu Bakar
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 26.11.2024
• Subjects: Hydrogen embrittlement; Irreversible H-Traps; Nanoscale precipitates; Nb micro-alloying; Press hardened steel; Retained austenite; Irreversible H-Traps; Retained austenite; Press hardened steel; Nb micro-alloying; Hydrogen embrittlement; Nanoscale precipitates
• ISSN: 0360-3199
• DOI: 10.1016/j.ijhydene.2024.10.244

Hydrogen embrittlement (HE) extant a substantial concern to press-hardened steel (PHS) owing to superior strength. The high strength to light-weight automobile structures necessitates the advancement of superior HE resistance PHS. This study investigated the HE susceptibility of Nb-microalloyed PHS by slow strain rate tensile testing, u-shaped constant bending load test, and thermal desorption spectroscopy. Nb enhances microstructure and HE resistance by introducing retained austenite, refining prior austenite grains (21.14–13.73 μm), forming low-angle grain boundaries, and nano-scale precipitates. Nb-alloyed steel exhibits no-cracking over 300 h under high pre-bending stress and decreases elongation loss up to 48% in hydrogen environment as compared to Nb-free steel. Diffusible H-content in 0.12 wt% Nb-steel reduces to 14.9% of that in Nb-free steel owing to enhanced hydrogen traps, the Fcc/Bcc matrix, and carbide precipitation. The multi-phase microstructure with nano-scale NbC precipitation impeded the localized H-dispersion, enhancing the HE resistance in PHS despite its high strength. [Display omitted] •Grain boundary strengthening achieved by refined microstructure in Nb-steel.•Retained austenite with NbC enhances hydrogen embrittlement resistance.•0.12 wt% Nb steel mitigate diffusible hydrogen content to 14.9% of that Nb-free steel.•Nb-alloying decreases elongation loss by up to 48% in presence of hydrogen.