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Hydrogen Embrittlement of Automotive Ultra-High-Strength Steels: Mechanism and Minimisation / JAMES LELLIOTT

Swansea University Author: JAMES LELLIOTT

DOI (Published version): 10.23889/SUthesis.62149

Abstract

Automotive manufacturers are increasingly using ultra-high-strength steels in vehicle components to facilitate mass reduction via downgauging. Unfortunately, as the strength of steels increases, so does susceptibility to ‘hydrogen embrittlement’, a process in which ductility is significantly impaire...

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Published: Swansea 2022
Institution: Swansea University
Degree level: Doctoral
Degree name: EngD
Supervisor: Sackett, Elizabeth; Figueroa-Gordon, Douglas
URI: https://cronfa.swan.ac.uk/Record/cronfa62149
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first_indexed 2022-12-08T15:22:05Z
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spelling 2022-12-08T15:36:54.8367735 v2 62149 2022-12-08 Hydrogen Embrittlement of Automotive Ultra-High-Strength Steels: Mechanism and Minimisation e8551b85fef0d6618f80f9a9fc311b05 JAMES LELLIOTT JAMES LELLIOTT true false 2022-12-08 Automotive manufacturers are increasingly using ultra-high-strength steels in vehicle components to facilitate mass reduction via downgauging. Unfortunately, as the strength of steels increases, so does susceptibility to ‘hydrogen embrittlement’, a process in which ductility is significantly impaired by ingress of hydrogen. Mechanisms and environmental conditions by which this degradation occurs are not fully understood. In this work, 2 fully-ferritic, 2 fully-martensitic boron, and 2 ferrite-martensite dual-phase, ultra-high-strength steels, were assessed for susceptibility to hydrogen embrittlement via 3 key characteristics: firstly, with particular regard to hydrogen evolution under corrosion conditions, through well-established open circuit potential and potentiodynamic polarisation experiments. Exacerbation of hydrogen evolution through galvanic corrosion of a zinc coating was assessed by scanning vibrating electrode technique (SVET), and an attempt made to quantify increased risk of hydrogen evolution during crevice corrosion through a novel time-lapse photography experiment. Secondly, hydrogen diffusivity was assessed via permeation experiments. Finally, degradation in mechanical properties due to diffusing hydrogen was evaluated through slow strain rate tests (SSRT), whereby susceptibility to embrittlement was equated to reduction in ductility of hydrogen-charged test specimens. The fully-ferritic steels showed the greatest resistance to mechanical degradation, attributed to micro-alloy nano-precipitates within their microstructure acting as ‘traps’, leading to lower diffusivity compared to dual-phase steels of equivalent strength. Indeed, lower diffusivity showed a strong correlation with lower levels of embrittlement across all steels. 1000 MPa dual-phase steel showed the greatest degradation in mechanical properties, with fully-martensitic boron steels also found to be particularly susceptible. 1000 MPa dual-phase steel also showed the largest increase in hydrogen evolution reaction in response to polarisation, thought to result from the inherent potential difference between ferrite and martensite phases. Galvanic corrosion of a damaged zinc coating was found to polarise the exposed steel substrate, triggering sufficient hydrogen evolution to reach critical concentrations for embrittlement. E-Thesis Swansea Embrittlement, Steel, Hydrogen, SSRT, Permeation, Corrosion 2 12 2022 2022-12-02 10.23889/SUthesis.62149 ORCiD identifier: https://orcid.org/0000-0002-3036-3326 COLLEGE NANME COLLEGE CODE Swansea University Sackett, Elizabeth; Figueroa-Gordon, Douglas Doctoral EngD Tata Steel 2022-12-08T15:36:54.8367735 2022-12-08T15:19:40.5739766 Faculty of Science and Engineering School of Engineering and Applied Sciences - Uncategorised JAMES LELLIOTT 1 62149__26047__71be331f29d14206926dced37551eb75.pdf Lelliott_James_A_EngD_Thesis_Final_Redacted_Signature.pdf 2022-12-08T15:28:08.7019511 Output 34863267 application/pdf E-Thesis – open access true Copyright: The author, James A. Lelliott, 2022. true eng
title Hydrogen Embrittlement of Automotive Ultra-High-Strength Steels: Mechanism and Minimisation
spellingShingle Hydrogen Embrittlement of Automotive Ultra-High-Strength Steels: Mechanism and Minimisation
JAMES LELLIOTT
title_short Hydrogen Embrittlement of Automotive Ultra-High-Strength Steels: Mechanism and Minimisation
title_full Hydrogen Embrittlement of Automotive Ultra-High-Strength Steels: Mechanism and Minimisation
title_fullStr Hydrogen Embrittlement of Automotive Ultra-High-Strength Steels: Mechanism and Minimisation
title_full_unstemmed Hydrogen Embrittlement of Automotive Ultra-High-Strength Steels: Mechanism and Minimisation
title_sort Hydrogen Embrittlement of Automotive Ultra-High-Strength Steels: Mechanism and Minimisation
author_id_str_mv e8551b85fef0d6618f80f9a9fc311b05
author_id_fullname_str_mv e8551b85fef0d6618f80f9a9fc311b05_***_JAMES LELLIOTT
author JAMES LELLIOTT
author2 JAMES LELLIOTT
format E-Thesis
publishDate 2022
institution Swansea University
doi_str_mv 10.23889/SUthesis.62149
college_str Faculty of Science and Engineering
hierarchytype
hierarchy_top_id facultyofscienceandengineering
hierarchy_top_title Faculty of Science and Engineering
hierarchy_parent_id facultyofscienceandengineering
hierarchy_parent_title Faculty of Science and Engineering
department_str School of Engineering and Applied Sciences - Uncategorised{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Engineering and Applied Sciences - Uncategorised
document_store_str 1
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description Automotive manufacturers are increasingly using ultra-high-strength steels in vehicle components to facilitate mass reduction via downgauging. Unfortunately, as the strength of steels increases, so does susceptibility to ‘hydrogen embrittlement’, a process in which ductility is significantly impaired by ingress of hydrogen. Mechanisms and environmental conditions by which this degradation occurs are not fully understood. In this work, 2 fully-ferritic, 2 fully-martensitic boron, and 2 ferrite-martensite dual-phase, ultra-high-strength steels, were assessed for susceptibility to hydrogen embrittlement via 3 key characteristics: firstly, with particular regard to hydrogen evolution under corrosion conditions, through well-established open circuit potential and potentiodynamic polarisation experiments. Exacerbation of hydrogen evolution through galvanic corrosion of a zinc coating was assessed by scanning vibrating electrode technique (SVET), and an attempt made to quantify increased risk of hydrogen evolution during crevice corrosion through a novel time-lapse photography experiment. Secondly, hydrogen diffusivity was assessed via permeation experiments. Finally, degradation in mechanical properties due to diffusing hydrogen was evaluated through slow strain rate tests (SSRT), whereby susceptibility to embrittlement was equated to reduction in ductility of hydrogen-charged test specimens. The fully-ferritic steels showed the greatest resistance to mechanical degradation, attributed to micro-alloy nano-precipitates within their microstructure acting as ‘traps’, leading to lower diffusivity compared to dual-phase steels of equivalent strength. Indeed, lower diffusivity showed a strong correlation with lower levels of embrittlement across all steels. 1000 MPa dual-phase steel showed the greatest degradation in mechanical properties, with fully-martensitic boron steels also found to be particularly susceptible. 1000 MPa dual-phase steel also showed the largest increase in hydrogen evolution reaction in response to polarisation, thought to result from the inherent potential difference between ferrite and martensite phases. Galvanic corrosion of a damaged zinc coating was found to polarise the exposed steel substrate, triggering sufficient hydrogen evolution to reach critical concentrations for embrittlement.
published_date 2022-12-02T04:21:33Z
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score 11.012678

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