Microstructure evolution of nanostructured ferritic alloy with and without Cr 3 C 2 coated SiC at high temperatures

This work focuses on fundamental understanding of microstructure evolution of nanostructured ferritic alloy (NFA) and 25 vol.% Cr 3 C 2 coated SiC(Cr 3 C 2 @SiC)-NFA composite during spark plasma sintering at 950 °C and the following thermal treatment at 1000 °C. A unique bi-phase microstructure with distinct Cr-rich and Si-rich phases has been observed for the 25 vol.% Cr 3 C 2 @SiC-NFA composite, while for the NFA sample, the traditional large grain microstructure remains. Grain sizes are significantly smaller for the 25 vol.% Cr 3 C 2 @SiC-NFA composite compared to those for the pure NFA, which can be attributed to the presence of grain boundary phases in the composite sample. During the thermal treatment, microstructure features can be directly correlated with the dissolution kinetics and phase diagrams calculated using Thermo-Calc/DICTRA/PRISMA®.