Pressure-less joining materials for SiC-based components for light water reactors

Silicon carbide fiber-reinforced composites (SiC/SiC) are leading candidates to replace zirconium-based alloys as cladding in light water reactors (LWR), owing to their exceptional oxidation resistance and mechanical performance under accident conditions. However, pressure-less joining methods compatible with the extreme chemical and thermal environment of LWRs remain a major technological hurdle. This work evaluates two promising joining materials—Mo-wrap (a MoSi₂/Si composite) and SAY (a silica–alumina–yttria glass-ceramic)—under simulated LWR conditions. Joining was performed using both conventional furnaces and laser-assisted techniques. Joint integrity and microstructure were assessed by SEM/EDS and X-ray computed tomography. Hydrothermal stability was evaluated in static and flowing-water (loop) autoclaves up to 30 days at 330 °C and 150–155 bar. Mo-wrap joints showed partial degradation due to silicon dissolution, while SAY joints retained good structural integrity in static tests but suffered phase-selective corrosion under flowing conditions, with keivite emerging as the most stable crystalline phase. Laser-processed amorphous SAY joints exhibited improved corrosion resistance, though still limited under prolonged exposure. These findings advance the understanding of joining performance in nuclear-relevant environments and support the development of accident-tolerant fuel cladding.