A study of the SiCf/SiC composite/Ni-based superalloy dissimilar joint brazed with a composite filler

Uniform and fine in-situ short-fiber/particle hybrid reinforcements were obtained in a SiCf/SiC composite/Ni-based superalloy joint by using a novel AuCuTiB/Mo/AuCuTiB composite filler. The growth of in-situ phases showed a strong dependence on the numbers of nucleation sites and metal atoms on the ceramic side. Inadequate brazing conditions adversely affected the formation of indirect TiB whiskers, and excessive brazing conditions induced an accumulation of metal atoms. As a result, the in-situ phases switched from Ti5Si3 + TiC to Ti5Si3 + Ni + TiB + TiC, and to (Ni, Ti)-(Si, C) + TiB with increasing brazing conditions. The size, type, and composition of the in-situ phases were effectively controlled by adjusting the brazing conditions (B content, brazing temperature, and holding time). In light of this, the shear strength of the joint was optimized at 124.9 MPa. The excellent mechanical performance was ascribed to (i) a suitable interfacial layer and (ii) the effective stress relief of in-situ phases and ductile/rigid/ductile multiple layers. Moreover, the joint exhibited mechanical stability at 973 K because the in-situ phases can serve as a high-temperature resistant second structure.