Concurrent Precipitation of Nb(C,N) and Metastable M23C6 in Alloy 347H at 700°C and 750°C: Computer Simulations and Comparison to Experiment

Michael V. Glazoff, Michael C. Gao, Laurent Capolungo, Michael P. Brady, Gabriel O. Ilevbare, Yukinori Yamamoto, Qing Qiang Ren, Jonathan D. Poplawsky, Jianguo Yu, Feng Zhang

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Abstract

We present our results for the concurrent precipitation of metastable M23C6, Nb(C,N) secondary precipitates, and the Nb(C,N) primary crystals in 347H austenitic stainless steel. For precipitation modeling, we have accounted for the elastic contribution to interfacial energy, and for the Fe-spin-polarization for NbC/Fe and M23C6/Fe interfacial energy values: for NbC/Fe ~ 0.63 J/m2. For M23C6 precipitates, an error function was used to describe the interfacial energy growth with particle size. In precipitation simulations, the average size of the primary Nb(C,N) particles remained ~ 1 μm at 700°C and ~ 0.3 μm at 750°C. The M23C6 precipitates at 750°C dissolved after 120 h (our simulations) compared to 300 h (experiments). The Nb(C,N)/Fe interfacial energy was not affected by the nitrogen additions. With these modifications, reasonable agreement with the available experimental data was obtained, which allows using them in the development of the 2nd-phase particle-informed creep theory.

Original languageEnglish
JournalJOM
DOIs
StateAccepted/In press - 2022

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