Title: Influence of high temperature sodium exposure on microstructure and material properties of AISI 440C stainless steel

Authors: S.C.S.P. Kumar Krovvidi; Chitta Ranjan Das; R. Punniyamoorthy; S. Chandramouli; K. Mariappan; B.K. Sreedhar; Jose Varghese; B.K. Nashine; Shaju K. Albert; S. Raghupathy

Addresses: Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102, India ' Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102, India ' Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102, India ' Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102, India ' Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102, India ' Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102, India ' Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102, India ' Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102, India ' Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102, India ' Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102, India

Abstract: AISI 440C SS is one of the candidate materials for bearings in sodium-cooled fast reactor systems due to its good mechanical strength and chemical inertness compared to other bearing steels such as 100Cr6. To understand the influence of sodium exposure at the operating temperature on the properties of the steel, a systematic study of exposing this material in static sodium for one month and eight months was carried out at 550°C and the change in the hardness and microstructure were studied. Bulk hardness reduced after 550°C sodium exposure (in both the specimens). Carbon depletion and formation of a thin soft layer was observed on the sodium-exposed surfaces of eight months specimen. The reduction in the hardness of the material reduces the life of the bearings and the formation of the soft layer decreases the wear resistance of the material. Hence, bearings of this material are limited up to 200°C.

Keywords: AISI 440C SS; bearings for SFR systems; sodium exposure; tempered martensite; leaching of carbon.

DOI: 10.1504/IJMATEI.2022.124205

International Journal of Materials Engineering Innovation, 2022 Vol.13 No.2, pp.73 - 86

Received: 09 Aug 2021
Accepted: 22 Sep 2021
Published online: 18 Jul 2022 *

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