Development of a NanoSIMS Methodology for the Assessment of Hydrogen Uptake in Corrosion Resistant Alloys

  • Yasser Al Aboura

Student thesis: Phd

Abstract

The recovery of oil and gas resources is becoming more challenging with time due to the highly demanding environments found in deep offshore wells. Hence, there is a need in the oil & gas (O&G) industry to improve knowledge on the topic of hydrogen embrittlement of high strength corrosion resistant alloys. Accurate hydrogen mapping is one of the main difficulties in tackling hydrogen damage and embrittlement of metallic alloys. Mapping hydrogen distribution in high strength metals will reveal a wealth of information on the local interaction of hydrogen with the various metallurgical features found in complex microstructures of high strength corrosion resistant alloys. The information will elucidate on the mechanisms of hydrogen embrittlement and act as input for designing effective alloys used in applications where exposure to hydrogen is expected. The NanoSIMS is a high-resolution SIMS imaging technique that has great potential for mapping hydrogen and deuterium in metallic alloys with high spatial resolution and sensitivity. The thesis focuses on exploring the capabilities of NanoSIMS in mapping hydrogen and deuterium in metallic alloys, with a specific interest in O&G nickel-based alloys. Several outcomes were achieved in this study. An experimental methodology/protocol for NanoSIMS analysis of hydrogen (deuterium) has been established uncovering unreported artefacts and a novel approach to mapping hydrogen and deuterium in alloys. The protocol was applied to map hydrogen (deuterium) distributions in austenitic stainless steel and precipitation hardened nickel-based superalloy. Results from the stainless steel investigations revealed localised deuterium enrichments in the as-received deformed condition as opposed to no localised enrichments observed in the solution annealed microstructure. The localised signals in the as-received alloys corresponded to deformation bands, alpha' martensite and MnS inclusions suggesting that such sites may be responsible for the initiation of hydrogen-induced cracking. The NanoSIMS results from the in-situ deuterium charging during slow strain rate cracking tests of nickel alloy 625+ revealed local enrichments at dislocation slip bands and grain boundary sigma phase. The results highlighted the importance of slip band formation and grain boundary metalloid segregation in determining hydrogen cracking susceptibility of high strength precipitation hardened nickel-based superalloys. Additionally, mapping of deuterium at delta phase and Laves phase has been successfully performed on a heat-treated alloy 625+ using the proposed methodology. The results revealed deuterium enrichments at the interface of delta phase and at the Laves phase.
Date of Award1 Aug 2020
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorDirk Engelberg (Supervisor) & Katie Moore (Supervisor)

Keywords

  • NanoSIMS artefacts
  • NanoSIMS
  • Hydrogen
  • Deuterium
  • Hydrogen trapping
  • Hydrogen induced cracking
  • Hydrogen/deuterium mapping

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