Aging degradation of cast stainless steel
A program is being conducted to investigate the significance of in-service embrittlement of cast duplex stainless steels under light-water reactor operating conditions. Microstructures of cast materials subjected to long-term aging either in reactor service or in the laboratory have been characterized by TEM, SANS, and APFIM techniques. Two precipitate phases, i.e., the Cr-rich ..cap alpha..' and Ni- and Si-rich G phase, have been identified in the ferrite matrix of the aged steels. The results indicate that the low-temperature embrittlement is primarily caused by ..cap alpha..' precipitates which form by spinodal decomposition. The relative contribution of G phase to loss of toughness is now known. Microstructural data also indicate that weakening of ferrite/austenite phase boundary by carbide precipitates has a significant effect on the onset and extent of embrittlement of the high-carbon CF-8 and CF-8M grades of stainless steels, particularly after aging at 400 or 450/sup 0/C. Data from Charpy-impact, tensile, and J-R curve tests for several heats of cast stainless steel aged up to 10,000 h at 350, 400, and 450/sup 0/C are presented and correlated with the microstructural results. Thermal aging of the steels results in an increase in tensile strength and a decrease in impact energy, J/sub IC/, and tearing modulus. The fracture toughness results show good agreement with the Charpy-impact data. The effects of compositional and metallurgical variables on loss of toughness are discussed.
- Research Organization:
- Argonne National Lab., IL (USA)
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 7181088
- Report Number(s):
- CONF-8610135-59; ON: DE87004939
- Country of Publication:
- United States
- Language:
- English
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Long-term embrittlement of cast duplex stainless steels in LWR systems: Semiannual report, October 1986-March 1987
Aging degradation of cast stainless steel
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36 MATERIALS SCIENCE
360103 -- Metals & Alloys-- Mechanical Properties
360106 -- Metals & Alloys-- Radiation Effects
AGING
ALLOYS
BWR TYPE REACTORS
CHROMIUM ALLOYS
CORROSION RESISTANT ALLOYS
CRYSTAL STRUCTURE
EMBRITTLEMENT
IRON ALLOYS
IRON BASE ALLOYS
MATERIALS
MATERIALS TESTING
MECHANICAL PROPERTIES
MICROSTRUCTURE
PHYSICAL RADIATION EFFECTS
PWR TYPE REACTORS
RADIATION EFFECTS
REACTOR MATERIALS
REACTORS
RESEARCH PROGRAMS
STAINLESS STEELS
STEELS
TESTING
WATER COOLED REACTORS
WATER MODERATED REACTORS