Brazing of metallized SiC ceramic to GH99 superalloy using graphene nanoplatelets reinforced AgCuTi composite filler.

Abstract A two-step process involving, first, the pre-metallization of the SiC ceramic, followed by the vacuum brazing using graphene nanoplatelets (GNPs) reinforced AgCuTi composite filler was developed to join SiC ceramic and GH99 superalloy. The metallization characteristics, joint microstructure and fracture behavior were investigated. Through pre-metallization, a smooth metallic coating formed on the SiC ceramic surface; the carbide layer adjacent to SiC ceramic had a semi-coherent interface with it. Brazing process showed that in situ synthesized TiC particles with fine-grains were evenly dispersed in the filler matrix due to GNPs acting as nucleation sites, promoting the refinement of microstructure of the joint. Moreover, the effect of GNPs in retarding the diffusion of metal atoms limited the reaction of Ti with Cu and Ni, thereby reducing the negative impact induced by the brittle compounds. The maximum shear strength of 26.4 MPa was obtained at AgCuTi-1%GNPs, which was ∼151.4% higher than the joint brazed using AgCuTi filler. [ABSTRACT FROM AUTHOR]