Influence of microstructure on hydrogen trapping and diffusion in a pre-deformed TRIP steel

Austenitic steels are known to exhibit a low hydrogen diffusion coefficient and hence a good resistance to hydrogen embrittlement. Therefore, it is an experimental challenge to investigate their hydrogen diffusion properties. In this study, the electrochemical perme-ation technique is used to determine the hydrogen diffusion coefficients in different pre -deformed states (4 = 0, 0.32, 0.39, 0.49) of the high-alloy austenitic TRIP steel X3CrMnNiMoN17-8-4 in a temperature range of 323 K-353 K. In combination with micro -structural analysis, a correlation between phase transformation from g-austenite to a'- martensite and dislocation density is shown. As a result of the lattice transformation from fcc to bcc, the diffusion rate of hydrogen is significantly increased (Dapp, 4 = 0-= 3.6 x 10-12 cm2 s-1, Dapp, 4 = 0.32 = 1.6 x 10-11 cm2 s-1at 323 K). With higher degrees of deformation, the dislocation density also increased in the martensite islands, resulting in a degressive growth of the diffusion coefficient (Dapp, 4 = 0.39 = 5.3 x 10-11 cm2 s-1, Dapp, 4 = 0.49 = 1.1 x 10-10 cm2 s-1at 323 K). Moreover, detailed calculations are performed to describe the way of hydrogen trapping and to give a possible mechanism of diffusion.(c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.