Diffusion bonding of FGH98 superalloy and DD5 single crystal using pure Ni interlayer

In this study, the FGH98 superalloy and DD5 single crystal were diffusion bonded using pure Ni interlayer under the pressure of 4 MPa. The elemental interdiffusion of Ni interlayer and base materials induced Ni3Al phases (γ’) reinforced Ni-based solid solution (γ) bonding seam (Ni layer zone), achieving the reliable joining of FGH98 and DD5. With the increase of diffusion bonding temperature, the elemental interdiffusion was promoted significantly, which was beneficial to the formation of γ’ phase in the joint. Due to the formation and enlargement of γ’ phase, the hardness of the Ni layer zone and the joint shear strength raised. The high diffusion bonding temperature (1160 ℃) resulted in γ’ phase bulk in the Ni layer zone, and the maximum joint strength of 630 MPa was achieved. However, the fracture of the joint obtained at 1160 ℃ was located in the Ni layer zone.