Effect of holding time and AgCuTi composite filler on microstructure and mechanical properties of GH4169/SiC vacuum brazed joints

The GH4169 superalloy and SiC ceramic were joined via vacuum brazing using AgCuTi filler and AgCuTi + Cu foam composite filler, respectively, to investigate their joint properties. The influence of holding time on the microstructure and shear strength of the GH4169/SiC joint was systematically investigated. The results revealed that the interface microstructure of the GH4169/SiC joint comprised the GH4169 superalloy/Ag (s, s) +Cu(s, s)/Ni3Ti/Ag(s, s)+ Cu(s, s)/Ti5Si3+TiC/SiC ceramic. As the holding time increased, elemental diffusion between the matrix and brazing filler became more pronounced, resulting in an increased thickness of the interfacial reaction layer (zones I and II), which enhanced the shear strength. The average shear strength of GH4169/SiC brazed joints, using both filler materials, initially increased and then decreased with prolonged holding time. The joint achieved a maximum shear strength of 43.7 MPa when brazed at 900 degrees C for 10 min using an AgCuTi+Cu foam composite filler. However, further increasing the holding time resulted in the complete dissolution of Cu foam, which negatively impacted the shear strength due to the increased content of brittle phases.