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Microstructural Evolution of Cast Austenitic Stainless Steels Under Accelerated Thermal Aging

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Proceedings of the 18th International Conference on Environmental Degradation of Materials in Nuclear Power Systems – Water Reactors

Part of the book series: The Minerals, Metals & Materials Series ((MMMS))

Abstract

Thermal aging degradation of cast austenitic stainless steels (CASS) was studied by electron microscopy to understand the mechanisms for thermal embrittlement potentially experienced during extended operations of light water reactor coolant systems. Four CASS alloys—CF3, CF3M, CF8, and CF8M—were thermally aged up 1500 h at 330 and 400 °C, and the microstructural evolution of the material was characterized by analytical aberration-corrected scanning transmission electron microscopy. The primary microstructural and compositional changes during thermal aging were spinodal decomposition of the δ-ferrite into α/α′, precipitation of G-phase in the δ-ferrite, segregation of solute to the austenite/ferrite interphase boundary, and growth of M23C6 carbides on the austenite/ferrite interphase boundary. These changes were shown to be highly dependent on aging temperature and chemical composition, particularly the amount of C and Mo. A comprehensive model is being developed to correlate the microstructural evolution with mechanical behavior and simulation.

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Acknowledgements

This research was sponsored by U.S. Department of Energy/Office of Nuclear Energy through Light Water Reactor Sustainability R&D Program and International Nuclear Energy Research Initiative (I-NERI) Program. Pacific Northwest National Laboratory is operated by Battelle Memorial Institute for the U.S. Department of Energy under Contract No. DEAC05-76RL01830. APT and FIB/SEM were performed at PNNL’s Environmental Molecular Sciences Laboratory, a Department of Energy—Office of Biological & Environmental Research national scientific user facility.

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Authors and Affiliations

  1. Nuclear Sciences Division, Energy and Environment Directorate, Pacific Northwest National Laboratory, 902 Battelle Blvd., Richland, WA, 99352, USA

    Timothy G. Lach & Thak Sang Byun

Authors
  1. Timothy G. Lach
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  2. Thak Sang Byun
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Corresponding author

Correspondence to Timothy G. Lach .

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Editors and Affiliations

  1. Idaho National Laboratory, Idaho Falls, ID, USA

    John H. Jackson

  2. Naval Nuclear Laboratory, Pittsburgh, PA, USA

    Denise Paraventi

  3. Chalk River Laboratories, Canadian Nuclear Laboratories, Chalk River, ON, Canada

    Michael Wright

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© 2019 The Minerals, Metals & Materials Society

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Lach, T.G., Byun, T.S. (2019). Microstructural Evolution of Cast Austenitic Stainless Steels Under Accelerated Thermal Aging. In: Jackson, J., Paraventi, D., Wright, M. (eds) Proceedings of the 18th International Conference on Environmental Degradation of Materials in Nuclear Power Systems – Water Reactors. The Minerals, Metals & Materials Series. Springer, Cham. https://doi.org/10.1007/978-3-030-04639-2_125

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