Effect of sodium environment on the creep-rupture and low-cycle fatigue behavior of austenitic stainless steels

Conference · Thu Sep 01 04:00:00 EDT 1977

OSTI ID:5056400

Natesan, K; Chopra, O K; Zeman, G J; Smith, D L; Kassner, T F

Austenitic stainless steels used for in-core structural components, piping, valves, and the intermediate heat exchanger in Liquid-Metal Fast-Breeder Reactors (LMFBRs) are subjected to sodium at elevated temperatures and to complex stress conditions. As a result, the materials can undergo compositional and microstructural changes as well as mechanical deformation by creep and cyclic fatigue processes. Information is presented on the creep-rupture and low-cycle fatigue behavior of Types 304 and 316 stainless steel in the solution-annealed condition and after long-term exposure to flowing sodium. The nonmetallic impurity-element concentrations in the sodium were controlled at levels similar to those in EBR-II primary sodium. Strain-time relationships developed from the experimental creep data were used to generate isochronous stress-creep strain curves as functions of sodium-exposure time and temperature. The low-cycle fatigue data were used to obtain relationships between plastic strain range and cycles-to-failure based on the Coffin-Manson formalism and a damage-rate approach developed at ANL. An analysis of the cyclic stress-strain behavior of the materials showed that the strain-hardening rates for the sodium-exposed steels were larger than those for the annealed material. However, the sodium-exposed specimens showed significant softening, as evidenced by the lower stress at half the fatigue life. Microstructural information obtained from the different specimens suggests that crack initiation is more difficult in the long-term sodium-exposed specimens when compared with the solution-annealed material. Based on the expected carbon concentrations in LMFBR primary system sodium, moderate carburization of the austenitic stainless steels will not degrade the mechanical properties to a significant extent, and therefore, will not limit the performance of out-of-core components.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL (United States)
• Sponsoring Organization: US Energy Research and Development Administration (ERDA)
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 5056400
• Report Number(s): CONF-771052-3
• Country of Publication: United States
• Language: English

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ALKALI METALS
ALLOYS
BREEDER REACTORS
CARBURIZATION
CHROMIUM ALLOYS
CHROMIUM STEELS
CHROMIUM-NICKEL STEELS
CORROSION RESISTANT ALLOYS
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IRON ALLOYS
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LIQUID METAL COOLED REACTORS
LMFBR TYPE REACTORS
MECHANICAL PROPERTIES
METALS
MOLYBDENUM ALLOYS
NICKEL ALLOYS
REACTOR COMPONENTS
REACTORS
SODIUM
STAINLESS STEEL-304
STAINLESS STEEL-316
STAINLESS STEELS
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