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

We performed mechanical testing and microstructural characterization 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 °C, 330 °C, 360 °C, and 400 °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 δ-ferrite into α/α', precipitation of G-phase in the δ-ferrite, segregation of solute to the austenite/ferrite interphase boundary, and growth of M 23C 6 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. Finally, the low C, high Mo CF3M alloys experienced the most spinodal decomposition and G-phase precipitation coinciding the largest reduction in impact properties.
Authors:
 [1] ;  [1] ;  [2]
  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Nuclear Sciences Division
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division
Publication Date:
Report Number(s):
PNNL-SA-126351
Journal ID: ISSN 0022-3115; PII: S0022311517307420
Grant/Contract Number:
AC05-76RL01830
Type:
Accepted Manuscript
Journal Name:
Journal of Nuclear Materials
Additional Journal Information:
Journal Volume: 497; Journal ID: ISSN 0022-3115
Publisher:
Elsevier
Research Org:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org:
USDOE Office of Nuclear Energy (NE); USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; thermal aging degradation; embrittlement; duplex stainless steel; spinodal decomposition; solute segregation; G-phase precipitation
OSTI Identifier:
1390578

Lach, Timothy G., Byun, Thak Sang, and Leonard, Keith J.. Mechanical property degradation and microstructural evolution of cast austenitic stainless steels under short-term thermal aging. United States: N. p., Web. doi:10.1016/j.jnucmat.2017.07.059.
Lach, Timothy G., Byun, Thak Sang, & Leonard, Keith J.. Mechanical property degradation and microstructural evolution of cast austenitic stainless steels under short-term thermal aging. United States. doi:10.1016/j.jnucmat.2017.07.059.
Lach, Timothy G., Byun, Thak Sang, and Leonard, Keith J.. 2017. "Mechanical property degradation and microstructural evolution of cast austenitic stainless steels under short-term thermal aging". United States. doi:10.1016/j.jnucmat.2017.07.059. https://www.osti.gov/servlets/purl/1390578.
@article{osti_1390578,
title = {Mechanical property degradation and microstructural evolution of cast austenitic stainless steels under short-term thermal aging},
author = {Lach, Timothy G. and Byun, Thak Sang and Leonard, Keith J.},
abstractNote = {We performed mechanical testing and microstructural characterization 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 °C, 330 °C, 360 °C, and 400 °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 δ-ferrite into α/α', precipitation of G-phase in the δ-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. Finally, the low C, high Mo CF3M alloys experienced the most spinodal decomposition and G-phase precipitation coinciding the largest reduction in impact properties.},
doi = {10.1016/j.jnucmat.2017.07.059},
journal = {Journal of Nuclear Materials},
number = ,
volume = 497,
place = {United States},
year = {2017},
month = {7}
}