Molten salt corrosion resistance of refractory complex concentrated alloys (RCCAs) for molten salt reactors

Refractory complex concentrated alloys (RCCAs) offer promising corrosion resistance and high-temperature stability for molten salt reactor (MSR) applications. In this study, MoNbTi and MoNbTiV RCCAs were developed and fabricated using electric field-assisted sintering (EFAS) and arc melting to investigate the effects of processing and composition on corrosion behavior. EFAS-processed alloys exhibited a fine body centered cubic (BCC) microstructure with Ti-rich secondary phase particles, while arc-melted alloys showed a single-phase BCC structure with minor interdendritic Ti segregation. Corrosion testing in molten NaCl-MgCl₂ salt at 700 °C for up to 1000 h revealed that EFAS-processed alloys suffered localized attack at Ti-rich sites, whereas arc-melted alloys demonstrated exceptional corrosion resistance with only slight Cl penetration after 1000 h. EFAS processed MoNbTiV outperformed MoNbTi due to its lower Ti content and reduced fraction of active secondary phases. The findings emphasize the importance of processing control and compositional optimization in achieving stable microstructures and superior corrosion resistance in RCCAs for MSR environments.