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Reduction of hydrogen embrittlement on Electrogalvanized Ultra High Strength Steels
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
2014 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Ultra-high strength steels is known to be susceptible for hydrogen embrittlement at very low concentrations of hydrogen. In this thesis three methods to prevent or reduce the hydrogen embrittlement in martensitic steel, with tensile strength of 1500 MPa, were studied. First, a barrier layer of aluminium designed to prevent hydrogen to enter the steel, which were deposited by vacuum evaporation. Second, a decarburization process of the steels surface designed to mitigate the induced stresses from cutting. Last, a hydrogen relief treatment at 150°C for 11 days and 200°C for 4 days, to reduce the hydrogen concentration in the steel. The effect of the hydrogen embrittlement was analyzed by manual measurements of the elongations after a slow strain rate testing at 5*10-6 mm/s, and the time to fracture in an in-situ constant load test with a current density of 1.92 mA/cm2 in a 0.5 M Na2SO4 solution. The barrier layer showed an increase in time to fracture, but also a decrease in elongations. The decarburized steel had a small increase in the time to fracture, but not enough to make it a feasible process. The hydrogen relief treatment showed a general decrease in hydrogen concentrations, but the elongation measurements was irregular although with a tendency for improvement. The simplicity of the hydrogen relief treatment makes it an interesting process to reduce the influence of hydrogen embrittlement. However, more investigations are necessary.

Place, publisher, year, edition, pages
2014. , 26 p.
Series
UPTEC K, ISSN 1650-8297 ; 14029
Keyword [en]
hydrogen embrittlement, electrogalvanized, ultra-high strength steel, martensite, vacuum evaporation, decarburization, hydrogen relief treatment
Keyword [sv]
väteförsprödning, elförzinkning, ultrahöghållfast stål, martensit, vakuumförångning, ytavkolning, väteutdrivning
National Category
Materials Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-236603OAI: oai:DiVA.org:uu-236603DiVA: diva2:767103
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Subject / course
Material
Educational program
Master Programme in Chemical Engineering
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Available from: 2014-12-15 Created: 2014-11-20 Last updated: 2014-12-15Bibliographically approved

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Department of Chemistry - Ångström
Materials Chemistry

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CiteExportLink to record
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