Microstructure control for high strength 9Cr ferritic-martensitic steels

L. Tan, D. T. Hoelzer, J. T. Busby, M. A. Sokolov, R. L. Klueh

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84 Scopus citations

Abstract

Ferritic-martensitic (F-M) steels with 9 wt.%Cr are important structural materials for use in advanced nuclear reactors. Alloying composition adjustment, guided by computational thermodynamics, and thermomechanical treatment (TMT) were employed to develop high strength 9Cr F-M steels. Samples of four heats with controlled compositions were subjected to normalization and tempering (N&T) and TMT, respectively. Their mechanical properties were assessed by Vickers hardness and tensile testing. Ta-alloying showed significant strengthening effect. The TMT samples showed strength superior to the N&T samples with similar ductility. All the samples showed greater strength than NF616, which was either comparable to or greater than the literature data of the PM2000 oxide-dispersion-strengthened (ODS) steel at temperatures up to 650°C without noticeable reduction in ductility. A variety of microstructural analyses together with computational thermodynamics provided rational interpretations on the strength enhancement. Creep tests are being initiated because the increased yield strength of the TMT samples is not able to deduce their long-term creep behavior.

Original languageEnglish
Pages (from-to)45-50
Number of pages6
JournalJournal of Nuclear Materials
Volume422
Issue number1-3
DOIs
StatePublished - Mar 2012

Funding

This research was sponsored by the US Department of Energy (DOE), Office of Nuclear Energy, for the FCRD & Gen-IV Research Program, under contract DE-AC05-00OR22725 with UT-Battelle, LLC. The Shared Research Equipment (SHaRE) User Facility at the ORNL was used to obtain the TEM results. The authors would like to express special thanks to Drs. T.S. Byun and Y. Yamamoto for their technical reviews and thoughtful comments.

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