Identification of Retained Austenite in 9Cr-1.4W-0.06Ta-0.12C Reduced Activation Ferritic Martensitic Steel

Rengachari Mythili,Ramanujam Govindaraj,Muraleedharan Vijayalakshmi,Loushambam Herojit Singh,Saibaba Saroja,Manvendra N Singh,Ravi Kirana,Anil K Sinha,Sudip K Deb

doi:10.3390/sym14020196

Abstract

Reduced activation ferritic martensitic (RAFM) 9Cr steels, which are candidate materials for the test blanket module (TBM) of nuclear fusion reactors, are considered to be air hardenable. However, alloy composition and the processing conditions play a significant role during the transformation of austenite to martensite/ferrite on cooling. The presence of retained austenite is known to influence the mechanical properties of the steel. Identifying very low amounts of retained austenite is very challenging though conventional microscopy. This paper aims at identifying a low amount of retained austenite in normalized 9Cr-1.4W-0.06Ta-0.12C RAFM steel using synchrotron X-ray diffraction and Mossbauer spectroscopy and confirmed by advanced automated crystal orientation mapping in transmission electron microscopy. Homogeneity of austenite has been understood to influence the microstructure of the normalized steel, which is discussed in detail.

Highlights

Reduced activation ferritic martensitic (RAFM) 9Cr steels are considered to be candidate materials for test blanket module (TBM) for nuclear fusion reactors, due to their excellent mechanical properties [1,2,3]
It is observed that the structure is martensitic in the normalized steel
Presence of undissolved primary carbides is observed in the normalized steel from Figure 1b

Summary

Introduction

Reduced activation ferritic martensitic (RAFM) 9Cr steels are considered to be candidate materials for test blanket module (TBM) for nuclear fusion reactors, due to their excellent mechanical properties [1,2,3]. They are a very good structural materials for steam generator circuits [4,5] as they exhibit good thermal conductivity and low thermal expansion coefficient [6,7]. The decomposition of austenite is known to be influenced by the rate of cooling (Q) from the austenitizing temperature and the alloy chemistry [11,12]

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Conclusion