Influence of alloying elements on the coarsening coefficients of M23C6 and M2B precipitates in a 10% Cr Belgorod steel

Abstract

A 10% Cr steel designed by ‘Belgorod State University’, has been considered in the present work in order to study the effect of alloying elements on the coarsening characteristics of precipitates. The stepped equilibrium diagram was constructed through the CALPHAD approach, employing the ThermoCalc software. The precipitates observed at the temperature of interest, i.e., 650 °C, were M23C6 (M=Cr, Fe), Laves phase, M2B, NbC and TiN. Amongst all the precipitates, M23C6 has the maximum phase fraction, i.e., 0.022. The magnitude of the coarsening coefficients for all the precipitates other than Laves phase, were observed to be of the order of 10-29 m3/s. In case of Laves phase, it was of the order of 10-31 m3/s. The variation of the coarsening coefficients of M23C6 and M2B, with respect to weight percent of alloying elements has been also investigated. It was observed that, with the increase in the weight percent of Co, Nb and W; the coarsening coefficients of M23C6 and M2B decrease. However, with the increase in weight percent of the V, the coarsening coefficients of M23C6 decrease and M2B increase.