Phase evolution of diffusion bonding interface between high Nb containing TiAl alloy and Ni-Cr-W superalloy

The diffusion bonding between high Nb containing TiAl alloy and Ni-Cr-W superalloy was carried out under the condition of 1000℃-50 MPa-60 min. The microstructure and the composition of diffusion bonding interface were characterized by optical microscope (OM), scanning electron microscope (SEM), energy disperse spectroscopy (EDS) and X-Ray diffraction (XRD). The phase evolutions of bonds with and without Ti/Cu interlayers were analyzed. The results indicate that the interfacial phases of high Nb containing TiAl alloy/Ni-Cr-W superalloy joint consist of γ-TiAl, Ni₂AlTi, Ni₃Ti, (NiCr)ss (ss represents solid solution), γ phase, while the interfacial phases of joint with Ti/Cu interlayers consist of Ti₃Al, Tiss, Ti₂Ni, rich Cu-NiAlTi, α₂-Wss, Ni₂AlTi, (NiCr)ss, γ phase. Besides, Cr and W atoms are concentrated in the zone near Ni-Cr-W superalloy because their diffusion is difficult. Ti/Cu foils can promote diffusion and reaction; therefore the micro-cracks in the bonded joint will be avoided efficiently.