Influence of prior austenite grain structure on hydrogen-induced fracture in as-quenched martensitic steels

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Journal Title
Journal ISSN
Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2023-03-28
Major/Subject
Mcode
Degree programme
Language
en
Pages
19
Series
Engineering Fracture Mechanics, Volume 281
Abstract
Suppressing hydrogen embrittlement in martensitic steels is a longstanding challenge. Here, we studied the effects of prior austenite grain (PAG) shape and size with a 0.25C steel utilising novel in situ H-charging, constant-displacement Tuning-fork testing (TFT) and H-permeation tests. Anisotropic elongated PAG structure has enhanced HE resistance transverse to the rolling direction (RD) with slower crack propagation rate (CPR) and quasi-cleavage fracture. Larger elongated grains are prone to intergranular fracture when crack propagates in RD. Reaustenitised equiaxed PAGs fail with intergranular cracking, which accelerates max CPR up to threefold compared to quasi-cleavage. All the microstructures have similar H-diffusion ∼5 × 10−7 cm2/s and density of reversible H-traps NT ∼ 3 × 1016, irrespective of PAG surface area, indicating that PAG boundaries are not effective diffusion paths. Deformed PAG boundaries mitigate susceptibility to intergranular cracking.
Description
Funding Information: This research was supported by Business Finland Oy, and projects ISA – Intelligent Steel Applications and FOSSA–Fossil-Free Steel Applications, are acknowledged. Academy of Finland (#337108) is thanked for funding, too. The authors wish to thank the technical staff of the Materials and Mechanical Engineering unit at the University of Oulu for their help with the experiments and sample preparation, and the work of Kaarlo Vähätaini with the loadcell clamp. Publisher Copyright: © 2023 The Authors
Keywords
Brittle fracture, Fractography, Hydrogen embrittlement, Steels
Other note
Citation
Latypova, R, Seppälä, O, Tun Nyo, T, Kauppi, T, Mehtonen, S, Hänninen, H, Kömi, J & Pallaspuro, S 2023, ' Influence of prior austenite grain structure on hydrogen-induced fracture in as-quenched martensitic steels ', Engineering Fracture Mechanics, vol. 281, 109090 . https://doi.org/10.1016/j.engfracmech.2023.109090