Hydrogen Embrittlement of the Precipitation Hardening Nickel-Based Alloy 718

Research output: ThesisMaster's Thesis

Abstract

With the urgency of the energy transition and in the context of climate change, hydrogen is gaining increasing importance as a promising alternative to fossil fuels. The key-challenge, however, is the safe transport and storage of significant quantities of the element. In this context, nickel-based alloys are of particular interest, as they are generally considered to be highly resistant to hydrogen embrittlement. However, occasional incidents of hydrogen embrittlement related failure, particularly within the oil and gas sector, have been noted with Inconel 718. This work focuses on the precipitation hardening nickel-based alloy Inconel 718, examined in three different heat treatment conditions, in order to identify potential differences regarding the susceptibility to hydrogen embrittlement. The slow strain rate technique with concomitant hydrogen charging as well as saturation simulations, implementing Python, were employed for characterization. A comprehensive microstructural analysis using scanning electron microscopy and atom probe tomography completed the experimental series. The initial segment of this thesis offers a detailed elaboration of the microstructure and precipitates in Inconel 718, as well as the behaviour of hydrogen within the alloy itself. These insights, along with the applied methods, form the scientific foundation for the conducted experiments, which are further supplemented by an in-depth discussion of the results. The alloy was analysed in both the homogenized condition and in two precipitation hardened states that differed in terms of precipitate size. The slow strain rate tests revealed a decrease in elongation at fracture, attributed to the presence of hydrogen. This serves as an indicator of embrittlement within the alloy. Moreover, the conjunction of insights derived from simulated hydrogen saturation curves and pertinent literature enabled the estimation of the influence of the individual applied heat treatments on the hydrogen diffusion rates as well as the sensitivity of Inconel 718 to hydrogen embrittlement.
Translated title of the contributionWasserstoffversprödung der ausscheidungshärtenden Nickelbasis-Legierung 718
Original languageEnglish
Awarding Institution
  • Montanuniversität
Supervisors/Advisors
  • Mori, Gregor Karl, Supervisor (internal)
Award date28 Jun 2024
Publication statusPublished - 2024

Bibliographical note

embargoed until 18-06-2027

Keywords

  • Nickel-Based Superalloys
  • Inconel 718
  • Precipitates
  • Hydrogen Embrittlement
  • Atom Probe Tomography
  • Slow Strain Rate Technique
  • Hydrogen Diffusion
  • Hydrogen Uptake
  • Hydrogen Saturation

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