Effect of 3D-SiO₂-fiber interlayer on SiC and Nb vacuum brazing

In order to solve the problems such as the less addition and agglomeration of enhanced particles, a new composite interlayer was introduced to assist in brazing between SiC and Nb. The composite interlayer was braided by SiO₂-fiber in three dimension with loose and porous structure (3D-SiO₂-fiber). The wettability of 3D-SiO₂-fiber, microstructure and mechanical property of the joints were analyzed by SEM, XRD and electronic universal testing machine. The results show that, when the content of Ti increased from 4.5% to 6.0%, the wetting angle of AgCu-Ti active filler metal on the surface of 3D-SiO₂-fiber interlayer decreased from 90° to 3°. The wettability was significantly improved. Moreover, the immersion depth of AgCu-Ti active filler metal in 3D-SiO₂-fiber interlayer increased continuously. With the increase of brazing temperature (950 ~980 ℃) and holding time (10 ~25 min), the reaction between 3D-SiO₂-fiber and AgCu-6.0Ti active filler metal was gradually full. This method not only ensured that 3D-SiO₂-fiber was able to be added to the filler metal in a large amount, but also Cu₃Si, TiSi, α-Ti and Ti₂Cu particles dispersed in the joint. So, the residual stress was relieved and the shear strength of joint was improved. Then the reliable joint between ceramic and metal was realized.