Spark plasma sintering of silicon carbide (SiC)-nanostructured ferritic alloy (NFA) composites with carbon barrier layer

Silicon carbide and nanostructured ferritic alloy (SiC-NFA) composites have the potential to maintain the outstanding irradiation resistance and enhance the mechanical integrity for nuclear cladding. By introducing a carbon reaction barrier on NFA (C@NFA), SiC-C@NFA composites are investigated in order to reduce the reaction between SiC and NFA in this work. The densities of the spark plasma sintered (SPS) SiC-C@NFA composites show an increasing trend with the SiC content to almost 100% dense. Although the SiC phase is absent, the Vickers hardness of the composites reaches 436-638 kgf/mm². The reaction leads to two types of regions in the composites, the NFA matrix and the micro-sized carbon enrich region, both of which contain extra Si element. The SiC-C@NFA composites show much improved microstructures and phases compared to the SiC-NFA composites without any coating, and the effectiveness of the carbon barrier is further verified based on the phase diagram and Gibbs free energy analysis. The SPS sintered SiC-C@NFA composites offer a new promising system for nuclear cladding.