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Picture for Modifying Martensitic Steels to Reduce Susceptibility to Hydrogen Embrittlement by Heat Treatment and Mo Addition

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Modifying Martensitic Steels to Reduce Susceptibility to Hydrogen Embrittlement by Heat Treatment and Mo Addition

Product Number: 51324-20964-SG

Author: Magdalena Eškinja; Gregor Mori; Gerald Winter; Jürgen Klarner; Holger Schnideritsch

Publication Date: 2024

$40.00

On a global scale there is a tendency to substitute fossil fuels with cleaner and renewable sources of energy. In recent years, hydrogen appears to be a promising alternative to achieve energy transition. In this context, the new infrastructure for the hydrogen transportation and storage should be considered. Exposure of high-strength steels to hydrogen can result in the deterioration of the mechanical properties by the mechanism of hydrogen embrittlement (HE). To prevent this phenomenon, pipeline steels can be modified by various means. One of the possible ways is to change the microstructural features by addition of carbide forming elements such as Mo. This paper aims to investigate the role of different Mo content as well as different heat treatment on susceptibility of two martensitic steels to HE. Hydrogen trapping behavior and permeation were investigated by means of electrochemical permeation test and Thermal Desorption Spectroscopy (TDS). Slow Strain Rate Tests (SSRT) of electrochemically charged steels were performed to elucidate mechanical performance. The carbide distribution and microstructure of the steels were observed using Scanning Electron Microscopy (SEM) and Electron Backscatter Diffraction (EBSD). The results implied that change of heat treatment leads to the control of Mo carbides size and dispersion and positively effects on HE susceptibility. Tempered martensitic steels with higher Mo content and modified heat treatment were found to be less susceptible to HE.

Picture for Susceptibility to Hydrogen Embrittlement of Engineering Steels with Martensitic Microstructures

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Susceptibility to Hydrogen Embrittlement of Engineering Steels with Martensitic Microstructures

Product Number: 51324-20800-SG

Author: Clara Herrera; Merlin Seifert

Publication Date: 2024

$40.00

Hydrogen emerged as a solution to increasing environmental problems and is becoming an important energy resource. However, hydrogen can deteriorate the mechanical performance of metallic components. This phenomenon is known as hydrogen embrittlement (HE). Engineering steels, such as nickel-chromium-molybdenum steels, are widely used in the industry and can be attractive materials for hydrogen applications such as pressure vessels, owing to a good combination of tensile strength (up to 1.1 GPa) and ductility (e.g., 10 % or higher). They can decrease product weight and reduce construction costs. However, as HE susceptibility tends to increase with increasing strength of steels, high-strength steels are susceptible to HE when used in hydrogen gas environment. The aim of this paper is to investigate the susceptibility of different engineering steels to hydrogen embrittlement. Three martensitic Cr-Ni-Mo steels were investigated. Slow strain rate tests were performed in gaseous hydrogen at 100 bar (10 MPa) and room temperature. Microstructure characterization and fractography study were carried out. Ni-Cr-Mo steels show a martensitic microstructure with precipitates in quenched and tempered condition. Their YS and UTS are higher than 1000 MPa (145 ksi) and 1100 MPa (159 ksi), respectively. Hydrogen gas degrades the ductility of Cr-Ni-Mo steels considerably, while strength deteriorates slightly. Fractography is characterized by a brittle fracture assisted by hydrogen. Hydrogen-Enhanced Localized Plasticity (HELP) is seen to be the primary failure mechanism in martensitic steels.

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