Mechanical property degradation and microstructural evolution of cast austenitic stainless steels under short-term thermal aging

JOURNAL OF NUCLEAR MATERIALS

卷:497

Article; Proceedings Paper

Lach, Timothy G.¹  Byun, Thak Sang¹  Leonard, Keith J.² 

[1] Pacific Northwest Natl Lab, Div Nucl Sci, Energy & Environm Directorate, 902 Battelle Blvd, Richland, WA 99352 USA

[2] Oak Ridge Natl Lab, Mat Sci & Technol Div, 1 Bethel Valley Rd, Oak Ridge, TN 37831 USA

关键词: Thermal aging degradation;    Embrittlement;    Duplex stainless steel;    Spinodal decomposition;    Solute segregation;    G-phase precipitation;   

DOI  :  10.1016/j.jnucmat.2017.07.059

来源: Elsevier

【 摘 要 】

Mechanical testing and microstructural characterization were performed on short-term thermally aged cast austenitic stainless steels (CASS) to understand the severity and mechanisms of thermal-aging degradation experienced during extended operation of light water reactor (LWR) coolant systems. Four CASS materials-CF3, CF3M, CF8, and CF8M-were thermally aged for 1500 h at 290 degrees C, 330 degrees C, 360 degrees C, and 400 degrees C. All four alloys experienced insignificant change in strength and ductility properties but a significant reduction in absorbed impact energy. The primary microstructural and compositional changes during thermal aging were spinodal decomposition of the delta-ferrite into alpha/alpha', precipitation of G-phase in the delta-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 chemical composition, particularly the concentration of C and Mo, and aging temperature. The low C, high Mo CF3M alloys experienced the most spinodal decomposition and G-phase precipitation coinciding the largest reduction in impact properties. (C) 2017 Elsevier B.V. All rights reserved.

【 授权许可】

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