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MM: Fachverband Metall- und Materialphysik

MM 19: Topical Session: Hydrogen in Materials: from Storage to Embrittlement II

MM 19.3: Talk

Tuesday, March 19, 2024, 11:00–11:15, C 130

Effect of retained austenite volume fraction on the hydrogen uptake and hydrogen embrittlement susceptibility of high-strength steels. — •Eric A.K. Fangnon and Yuriy Yagodzinskyy — Department of Mechanical Engineering, School of Engineering, Aalto University, P.O Box 11000, FI-00076, Espoo, Finland

Retained austenite (RA) is known for playing a dual role in the way hydrogen interacts with steels affecting their resistance or susceptibility to HE. In this study, we investigate the performance of five distinct high-strength steels with varying volume fractions of RA (0 - 35%) obtained from different alloying and heat-treatment processes. Electrochemical hydrogen charging under monotonic and cyclic loading modes was used to evaluate the steel's performance in hydrogenated conditions. In addition, the effect of RA on hydrogen uptake and phase transformation under load was investigated by thermal desorption spectroscopy, X-ray diffraction, and electron backscatter diffraction analysis. The Results show that there is a threshold at which the benefits of RA exist. After which the steels manifest severe susceptibility to HE as a function of RA volume fraction Via intergranular fracture modes for steels with higher contents of RA. Different hydrogen uptake and trapping were observed for the steels as a function of RA volume fraction, Load magnitude, and time. On phase transformation under load and continuous hydrogen charging, local variations in the measured RA that can be associated with the loading mode and hydrogen concentration were observed. γ-Fe into α-Fe may be specifically localized near the crack tips requiring further studies.

Keywords: high-strength steels; hydrogen embrittlement; retained austenite; Phase transformation; thermal desorption spectroscopy