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

Abstract The GH4169 superalloy and SiC ceramic were subjected to vacuum brazing using AgCuTi filler and AgCuTi + Cu foam composite filler, respectively. The influence of holding time on the microstructure and shear strength of the joint between GH4169 and SiC was investigated. The results demonstrate that the interface microstructure of the GH4169/SiC joint consists of the GH4169 superalloy/Ag (s, s) +Cu(s,s) /TiNi3+Ti (Cu, Ni)2+Ag(s, s)+ Cu(s,s) +Ti5Si3+TiC /SiC ceramic. As the holding time increases, there is a more pronounced diffusion of elements between the matrix and brazing filler, leading to an increased thickness of the interfacial reaction layer (zones I and II), which facilitates an enhancement in shear strength. The average shear strength of GH4169/SiC brazed joints, obtained using two different filler materials, initially increases and then decreases with prolonged insulation time. The joint achieves a maximum shear strength of 43.7 MPa when brazed at 900 ℃ for 10 minutes using an AgCuTi+Cu foam composite filler. However, a further increased holding time leads to the complete dissolution of Cu foam and an increase in Ti-Cu intermetallic compounds, which is detrimental to shear strength due to the rise in brittle phase content.