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

Abstract

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 hours 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. A comprehensive model is being developed to correlate the microstructural evolution with mechanical behavior and simulation for predictive evaluations of LWR coolant system components.

Authors:
; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE Office of Nuclear Energy (NE)
OSTI Identifier:
1411902
Report Number(s):
PNNL-SA-126351
Journal ID: ISSN 0022-3115; 49663; 830403000
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Nuclear Materials; Journal Volume: 497; Journal Issue: C
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; Environmental Molecular Sciences Laboratory

Citation Formats

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., 2017. 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. Fri . "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.
@article{osti_1411902,
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 = {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 hours 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. A comprehensive model is being developed to correlate the microstructural evolution with mechanical behavior and simulation for predictive evaluations of LWR coolant system components.},
doi = {10.1016/j.jnucmat.2017.07.059},
journal = {Journal of Nuclear Materials},
number = C,
volume = 497,
place = {United States},
year = {Fri Dec 01 00:00:00 EST 2017},
month = {Fri Dec 01 00:00:00 EST 2017}
}