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Effect of Nb on Thermal-Shock Resistance of Austenitic Heat Resistant Cast Steel
Tetsuya OkuyamaTakumi HigashizonoNgo Huynh Kinh LuanMasaki Kudo
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JOURNAL FREE ACCESS Advance online publication

Article ID: MT-M2020121

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Abstract

The effect of Nb on microstructure and thermal-shock resistance was investigated for as cast and annealed JIS SCH21 steels. Primary NbC carbide were crystallized together with M23C6 at grain boundary in as cast steel. Decomposition of primary M23C6 was detected, while NbC was also hardly decomposed when annealed at elevated temperature. It was found that chromium carbides had low thermal stability but primary NbC carbides played a role in preventing propagation of micro-cracks and restraining shape deformation under condition both heating and quenching. As a result, thermal-shock resistance was improved in the Nb-added steel.

 

This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 83 (2019) 474–478.

Fig. 12 Partitioning of alloying elements analyzed by STEM-EDS for micro-crack in Nb steel occurred when thermal shocked at 1223 K for 300 cycles. Fullsize Image
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