Effect of prior austenite grain morphology on hydrogen embrittlement behaviour under plastic straining in as-quenched 500 HBW steels

Renata Latypova*, Tun Tun Nyo, Oskari Seppälä, Eric Fangnon, Yuriy Yagodzinskyy, Saara Mehtonen, Hannu Hänninen, Jukka Kömi, Sakari Pallaspuro

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

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Prior austenite grain (PAG) structure is an important factor influencing hydrogen embrittlement (HE) susceptibility of ultrahigh-strength steels. In this study, the effect of PAG shape and size on HE behaviour is investigated using a novel tuning-fork testing method and hydrogen thermal desorption spectroscopy (TDS). Different PAG structures were acquired via re-austenitization (860 °C = A860, 960 °C = A960) and rapid quenching of an as-received 500 HBW direct-quenched (DQ) steel, which has an auto-tempered lath-martensitic microstructure and elongated PAG morphology. Fractography reveals different crack propagation mechanisms depending on the PAG shape. With the elongated PAG structure, hydrogen-induced crack propagation transverse to elongated PAGs was transgranular quasi-cleavage. Propagation was partially intergranular with the equiaxed PAG structures, regardless of the PAG size, leading to equally faster fracture. The TDS results show that there are no significant differences between the total hydrogen contents, but re-austenitized A860 and A960 steels contain a higher fraction of weakly trapped hydrogen. This indicates that the PAG boundaries are not the dominant hydrogen traps, and the different crack propagation mechanisms are rather linked to the geometrical shape of the grain structure.

Original languageEnglish
Title of host publication23rd European Conference on Fracture, ECF 2022
EditorsPedro Moreira, Luis Reis
Number of pages8
ISBN (Electronic)978-1-7138-7030-2
Publication statusPublished - 2022
MoE publication typeA4 Conference publication
EventEuropean Conference on Fracture - Funchal, Portugal
Duration: 27 Jun 20221 Jul 2022
Conference number: 23

Publication series

NameProcedia Structural Integrity
ISSN (Electronic)2452-3216


ConferenceEuropean Conference on Fracture
Abbreviated titleECF


  • hydrogen embrittlement
  • prior austenite grain structure
  • steel
  • TDS
  • tuning-fork test


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