Issue 51

M. Cauwels et alii, Frattura ed Integrità Strutturale, 51 (2020) 449-458; DOI: 10.3221/IGF-ESIS.51.33 449 Focussed on the 1st Benelux Network Meeting and Workshop on Damage and Fracture Mechanics The hydrogen embrittlement sensitivity of duplex stainless steel with different phase fractions evaluated by in-situ mechanical testing Margo Cauwels, Lisa Claeys, Tom Depover, Kim Verbeken Ghent University, Department of Materials, Textiles and Chemical Engineering, Technologiepark 46, 9052 Zwijnaarde, Belgium Margo.Cauwels@UGent.be Lisa.Claeys@UGent.be Tom.Depover@UGent.be, http://orcid.org/0000-0002-8856-1122 Kim.Verbeken@UGent.be, http://orcid.org/0000-0002-5190-016X A BSTRACT . The influence of the austenite ( γ) phase fraction on the hydrogen embrittlement of duplex stainless steel is investigated. Heat treatments are performed to create two duplex stainless steel specimens, containing 50% and 44% of austenite, respectively. Mechanical testing with and without hydrogen charging reveals that significant embrittlement occurs regardless of the austenite fraction. A higher austenite fraction results in a reduced ductility loss under the presence of hydrogen. Samples with a higher ferrite fraction are embrittled more due to their higher hydrogen diffusivity. In-situ tensile tests, interrupted at the ultimate tensile strength, show hydrogen-assisted cracks on the specimen surface both in austenite and ferrite and across the α/γ interface. K EYWORDS . Hydrogen embrittlement; Duplex stainless steel; In-situ mechanical testing Citation: Cauwels, M., Claeys, L., Depover, T., Verbeken, K., The hydrogen embrittlement sensitivity of duplex stainless steel with different phase fractions evaluated by in-situ mechanical testing, Frattura ed Integrità Strutturale, 51 (2020) 449-458. Received: 31.10.2019 Accepted: 03.12.2019 Published: 01.01.2020 Copyright: © 2019 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION uplex stainless steels (DSS) are a family of stainless steel grades characterised by a mixed microstructure of austenite (γ, FCC crystal structure) and ferrite (α, BCC crystal structure). They combine high mechanical strength with excellent corrosion resistance. DSS are therefore attractive materials for application in a diverse range of industries, such as energy, marine, petrochemical, paper and oil & gas industry. Their use has largely increased during the last decade. However, DSS have an important drawback: they are vulnerable to hydrogen embrittlement (HE) and hydrogen induced stress cracking (HISC) [1, 2]. Hydrogen embrittlement is used to refer to a degradation of mechanical properties due to the presence of hydrogen. This phenomenon is mostly reported as a decrease in material ductility and toughness, which can lead to unexpected and premature failure. Hydrogen can enter the DSS during production and processing, for example during welding, or during in-service conditions, such as for cathodically over-protected offshore structures or because of general corrosion that can be aggravated in environments where H 2 S is present [3–5]. D