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This study investigated the effect of cyclic heat treatment on the resistance of tempered martensitic steels to hydrogen embrittlement. The cyclic heat treatment not only refined the prior austenite grain sizes from approximately 30 to 5 μm but also reduced the initial dislocation density. The change in microstructure by the cyclic heat treatment did not result in obvious differences in the mechanical properties compared with those of simple quenched and tempered steel when hydrogen was not introduced into the specimens. Hydrogen charging caused intergranular and quasi-cleavage cracking, and both cracking modes were restricted by cyclic heat treatment. An important feature observed in the steel subjected to cyclic heat treatment was frequent crack deflection and crack tip blunting, which occurred at block and prior austenite grain boundaries (triple junctions). Therefore, grain refinement increased the probability of crack deflection and crack tip blunting. In addition, the relatively low dislocation density in cyclically heat-treated steel is believed to contribute to the suppression of plasticity-related damage nucleation, which is critically important for quasi-cleavage cracking.

Rights:

• Creative Commons BY Attribution 4.0 International
  

Keyword: Hydrogen embrittlement, Martensitic steel, Grain size

Date published: 2024-05-24

Publisher: Elsevier BV

Journal:

• International Journal of Hydrogen Energy (ISSN: 03603199) vol. 136 p. 731-741

Funding:

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.1016/j.ijhydene.2024.05.327

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Updated at: 2025-05-29 16:30:11 +0900

Published on MDR: 2025-05-29 16:19:48 +0900