Influence of SiC content in B ₄ C– n SiC composites corrosion in molten FLiNaK salt at 800°C

Abstract The present study investigates the influences of SiC incorporation on the microstructure and corrosion behavior of B ₄ C– n SiC composites in molten FLiNaK salt at 800°C. The corrosion characteristics and mechanisms of B ₄ C– n SiC composites in molten FLiNaK salt were thoroughly characterized and extensively discussed. The B ₄ C– n SiC composites exhibited a more refined grain size and lowered apparent porosity as the SiC content increased. Additionally, the concentration of high‐angle grain boundaries (HAGBs) in B ₄ C– n SiC composites increased as the SiC content increased. The incorporation of 10 wt.% SiC improved the corrosion resistance of B ₄ C– n SiC composites against molten FLiNaK salt. However, the incorporation of excessive SiC (≥20 wt.%) did not improve the corrosion resistance. The best corrosion resistance of B ₄ C–10% SiC ceramic composite was attributed, on the one hand, to its relatively low apparent porosity and the low concentration of HAGBs with high structural disorder. On the other hand, the selective corrosion of B ₄ C in B ₄ C–10% SiC ceramic composite rapidly formed a sufficiently thick and highly graphitized C‐rich layer on its surface during the initial stages of the corrosion test. The C‐rich layer maintained the integral structure of the ceramic and prevented subsequent corrosive medium from penetrating into the ceramic.