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

[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.

[发布日期] 2017-12-15

[效力级别]  Proceedings Paper

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