Compositional characterisation and thermodynamic modelling of nitride precipitates in a 12% Cr steel

In 9–12% Cr steels, nitrides (MX, M2X) and modified Z-phase ((Cr, V, Nb, Fe)N)) are of special interest because of their different contribution to the creep strength of the material. The changes in the chemical composition of complex nitrides and their crystallography were investigated using transmission electron microscopy. A method based on multiple linear least squares fit procedures was applied to extract the complete element content of the nitrides from the electron energy loss spectra. These results, augmented by X-ray spectroscopic data, were compared with the outcomes of the thermodynamic model implemented in the software package MatCalc. The elemental concentrations of precipitates under study i. e. the M2X, MX and modified Z-phase are in good agreement with simulations.