Silicon carbide based joining materials for fusion energy and other high-temperature, structural applications

Three methods for obtaining joints consisting of silicon carbide based material were evaluated: reaction-forming, reaction bonding, and pyrolysis of preceramic polymers. Joints were successfully fabricated without evidence of deleterious reactions with silicon carbide substrates. A direct comparison of the bending strength and through-thickness shear strength of butt joints was made using four-point bending and asymmetric four-point bending. The values of the bending strengths varied from 53-134 MPa. The through-thickness shear strength of the reaction formed was approximately 40% of the bend strength. Reaction-formed joints between composites were stronger than those between monolithic substrates. Various joints were heat treated at 1100°C, in flowing argon, for 100 h to investigate the high temperature stability of the joints. The bending strength of the reaction bonded joints improved, the bending strength of polymer derived joints did not change significantly, and the through-thickness shear strength of a reaction-formed joints decreased.