Transmission electron microscopy of oxide development on 9Cr ODS steel in supercritical water

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Abstract

Oxide layers formed on 9Cr oxide dispersion strengthened ferritic steel alloys during exposure to 600 °C supercritical water for 2- and 4-weeks were examined using cross-sectional transmission electron microscopy. A focused ion beam in situ lift-out technique was used to produce site-specific samples with electron transparent areas up to 8 μm by 10 μm. The oxide layers consist of several sub-layers: an Fe-rich outer oxide, a Cr-rich inner oxide, and a diffusion layer, extending beyond the oxide front into the metal. An evolution of the oxide layer structure is seen between 2 and 4 weeks, resulting in the development of a band of Cr2O3 at the diffusion layer/metal interface from the previously existing continuous mixture of FeCr2O4 'fingers' and bcc metal. It is believed that transport in this Cr2O3 layer at the diffusion layer/metal interface becomes the rate-limiting step for oxide advancement, since this change in oxide structure also corresponds to a decrease in corrosion rate.

Original languageEnglish (US)
Pages (from-to)280-285
Number of pages6
JournalJournal of Nuclear Materials
Volume392
Issue number2
DOIs
Publication statusPublished - Jul 15 2009

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All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Materials Science(all)
  • Nuclear Energy and Engineering

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