Low temperature air braze process for joining silicon carbide components used in heat exchangers, fusion and fission reactors, and other energy production and chemical synthesis systems

Fabrication of large, or complex, components from silicon carbide, or other technical ceramics, used in heat exchanger devices, energy production and chemical synthesis systems, and for components within fusion and fission reactors require robust joining processes. Ceramatec has developed a novel method for achieving bonds using an air brazing process. For silicon carbide joining, the braze acts under certain conditions to promote diffusion bonding. The resulting joined regions are thought to form by rapid interdiffusion of the diffusion-enhancing braze material and silicon and carbon species, resulting in a microstructure more similar to one formed by diffusion bonding than brazing. Processing of these joints is accomplished at relatively low temperatures, 900°C-1200°C in air, with minimal applied load. The brazed joint strength was found to be statistically equivalent to monolithic control samples at room temperature. Oxidation testing, using dry oxygen and saturated steam, was conducted at 1000°C for 1000 hours on joined specimens, resulting in further microstructural development of the joint, with subsequent shear testing showing no appreciable reduction in strength. Torsion tests on irradiated joined samples show that the joint’s mechanical integrity is resistant to radiation degradation.