Accelerated aging embrittlement of cast duplex stainless steel: Activation energy for extrapolation

Conference · Mon May 01 04:00:00 EDT 1989

OSTI ID:5651597

Chung, H M; Chopra, O K

Cast duplex stainless steels, used extensively in LWR systems for primary pressure boundary components such as primary coolant pipes, valves, and pumps, are susceptible to thermal aging embrittlement at reactor operating or higher temperatures. Since a realistic aging embrittlement for end-of-life or life-extension conditions (i.e., 32--50 yr of aging at 280--320{degree}C) cannot be produced, it is customary to simulate the metallurgical structure by accelerated aging at {approximately}400{degree}C. Over the past several years, extensive data on accelerated aging have been reported from a number of laboratories. The most important information from these studies is the activation energy, namely, the temperature dependence of the aging kinetics between 280 and 400{degree}C, which is used to extrapolate the aging characteristics to reactor operating conditions. The activation energies (in the range of 18--50 kcal/mole) are, in general, sensitive to material grade, chemical composition, and fabrication process, and a few empirical correlations, obtained as a function of bulk chemical composition, have been reported. In this paper, a mechanistic understanding of the activation energy is described on the basis of the results of microstructural characterization of various heats of CF-3, -8, and -8M grades that were used in aging studies at different laboratories. The primary mechanism of aging embrittlement at temperatures between 280 and 400{degree}C is the spinodal decomposition of the ferrite phase, and M{sub 23}C{sub 6} carbide precipitation on the ferrite/austenite boundaries is the secondary mechanism for high-carbon CF-8 grade. 20 refs., 10 figs., 3 tabs.

• Research Organization: Argonne National Lab., IL (USA)
• Sponsoring Organization: NRC
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 5651597
• Report Number(s): CONF-890820-5; ON: DE90001773
• Country of Publication: United States
• Language: English

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36 MATERIALS SCIENCE
360101 -- Metals & Alloys-- Preparation & Fabrication
360103* -- Metals & Alloys-- Mechanical Properties
ACTIVATION ENERGY
AGING
ALLOYS
BWR TYPE REACTORS
CARBIDES
CARBON COMPOUNDS
CHEMICAL COMPOSITION
CHROMIUM
CONTROL EQUIPMENT
COOLING SYSTEMS
CRYSTAL STRUCTURE
ELEMENTS
EMBRITTLEMENT
ENERGY
ENERGY SYSTEMS
EQUIPMENT
FABRICATION
FLOW REGULATORS
HEAT TREATMENTS
HIGH ALLOY STEELS
IRON ALLOYS
IRON BASE ALLOYS
KINETICS
METALS
MICROSTRUCTURE
PIPES
PRIMARY COOLANT CIRCUITS
PWR TYPE REACTORS
REACTOR COMPONENTS
REACTOR COOLING SYSTEMS
REACTORS
SEGREGATION
STAINLESS STEELS
STEELS
TEMPERATURE DEPENDENCE
TRANSITION ELEMENTS
VALVES
WATER COOLED REACTORS
WATER MODERATED REACTORS