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Understanding passive film degradation and its effect on hydrogen embrittlement of super duplex stainless steel - Synchrotron X-ray and electrochemical measurements combined with CalPhaD and ab-initio computational studies

DOI: 10.1016/j.apsusc.2023.157364 DOI Help

Authors: Cem Ornek (Istanbul Technical University; Leibniz Institute for Materials Research) , Fan Zhang (University of Sussex) , Alfred Larsson (Lund University) , Mubashir Mansoor (Istanbul Technical University) , Gary S. Harlow (Malmö University) , Robin Kroll (The University of Manchester) , Francesco Carla (Diamond Light Source) , Hadeel Hussain (Diamond Light Source) , Dirk L. Engelberg (The University of Manchester) , Bora Derin (Istanbul Technical University) , Jinshan Pan (KTH Royal Institute of Technology)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Applied Surface Science , VOL 628

State: Published (Approved)
Published: August 2023
Diamond Proposal Number(s): 23388

Open Access Open Access

Abstract: The passive film stability on stainless steel can be affected by hydrogen absorption and lead to microstructure embrittlement. This work shows that the absorption of hydrogen results in surface degradation due to oxide reduction and ionic defect generation within the passive film, which decomposes and eventually vanishes. The passive film provides a barrier to entering hydrogen, but when hydrogen is formed, atomic hydrogen infuses into the lattices of the austenite and ferrite phases, causing strain evolution, as shown by synchrotron x-ray diffraction data. The vacancy concentration and hence the strains increase with increasing electrochemical cathodic polarization. Under cathodic polarization, the surface oxides are thermodynamically unstable, but the complete reduction is kinetically restrained. As a result, surface oxides remain present under excessive cathodic polarization, contesting the classical assumption that oxides are easily removed. Density-functional theory calculations have shown that the degradation of the passive film is a reduction sequence of iron and chromium oxide, which causes thinning and change of the semiconductor properties of the passive film from n-type to p-type. As a result, the surface loses its passivity after long cathodic polarization and becomes only a weak barrier to hydrogen absorption and hence hydrogen embrittlement.

Journal Keywords: Passive film; Cathodic polarization; Super duplex stainless steel; Hydrogen embrittlement; Ab-initio density-functional theory; FactSage thermodynamics

Diamond Keywords: Alloys

Subject Areas: Materials, Chemistry, Social Sciences

Instruments: I07-Surface & interface diffraction

Added On: 03/05/2023 09:50


Discipline Tags:

Surfaces Physics Physical Chemistry Chemistry Corrosion Materials Science interfaces and thin films Metallurgy

Technical Tags:

Diffraction Grazing Incidence X-ray Diffraction (GIXD) X-ray Reflectivity (XRR)