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

Lach, Timothy G.; Byun, Thak Sang; Leonard, Keith J.

doi:10.1016/j.jnucmat.2017.07.059

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

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Abstract

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.

Authors:

Lach, Timothy G. ^[1]; Byun, Thak Sang ^[1]; Leonard, Keith J. ^[2]

Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Nuclear Sciences Division
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division

Publication Date:: Mon Jul 31 00:00:00 EDT 2017

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)

OSTI Identifier:: 1390578

Alternate Identifier(s):: OSTI ID: 1549663

Report Number(s):: PNNL-SA-126351
Journal ID: ISSN 0022-3115; PII: S0022311517307420

Grant/Contract Number:: AC05-76RL01830; DEAC05-76RL01830

Resource Type:: Accepted Manuscript

Journal Name:: Journal of Nuclear Materials

Additional Journal Information:: Journal Volume: 497; Journal ID: ISSN 0022-3115

Publisher:: Elsevier

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

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.

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                    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.  https://doi.org/10.1016/j.jnucmat.2017.07.059

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                    Lach, Timothy G., Byun, Thak Sang, and Leonard, Keith J. Mon .  
"Mechanical property degradation and microstructural evolution of cast austenitic stainless steels under short-term thermal aging".  United States.  https://doi.org/10.1016/j.jnucmat.2017.07.059.  https://www.osti.gov/servlets/purl/1390578.

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@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         = {Mon Jul 31 00:00:00 EDT 2017},

  month        = {Mon Jul 31 00:00:00 EDT 2017}

}

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