Embrittlement of laboratory- and reactor-aged CF-3, CF-8, and CF-8M duplex stainless steels

Conference · Sun Oct 01 04:00:00 EDT 1989

OSTI ID:5422320

Chung, H M; Leax, T R ^[1]

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1. Argonne National Lab., IL (USA)

Cast duplex stainless steels of CF-3, CF-8, and CF-8M grades, containing a wide range of chemical composition and ferrite content, were aged in the laboratory at 270 to 450{degree}C to evaluate the kinetics and mechanisms of thermal-aging embrittlement. CF-8 and CF-8A steels were also obtained from components of BWRs and PWRs after service of 12 to 22 yr. After mechanical-property (i.e., Charpy impact, tensile, and J-R curve) and microhardness tests, the aged specimens were examined by transmission electron microscopy and field-ion atom-probe techniques to elucidate the aging mechanisms and identify critical factors that control the embrittlement kinetics. From the results of microstructural characterization, the primary and secondary embrittlement mechanisms were identified. A mechanistic correlation was obtained between the microstructural characteristics and the activation energy of aging (i.e., the temperature dependence of the aging kinetics) for steels with a range of chemical compositions and subjected to different fabrication and thermal-treatment conditions. The unified correlation, based on spinodal decomposition influenced by G-phase nucleation and growth in ferrite and M{sub 23}C{sub 6} precipitation on ferrite-austenite boundaries, provides a good explanation of the complex behavior of the activation energy (ranging from 18 to 55 kcal/mole) regardless of grade, chemical composition, or fabrication process. 27 refs., 13 figs., 6 tabs.

• Research Organization: Argonne National Lab., IL (USA)
• Sponsoring Organization: NRC
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 5422320
• Report Number(s): CONF-8908175-1; ON: DE90002777
• Country of Publication: United States
• Language: English

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