Diffusion bonding of nickel-based powder metallurgy superalloy FGH98 with pure nickel interlayer

FGH98 powder metallurgy superalloy were successfully bonded via diffusion bonding technique with pure Ni interlayer. It was indicated that adding the Ni interlayer can significantly reduce joint defects, promote elements diffusion, and improve the bonding rate comparing with direct diffusion bonded joint. The typical joint is clearly divided into the IZ with larger volume dendritic γ′ phase and the DZ with narrow primary γ′ phase, petal secondary γ′ phase and granular tertiary γ′ phase. It was observed that the thinner the interlayer, the easier it is for the joint to achieve alloying, the more uneven the transition of the joint structure. Properly increasing the temperature or holding time can help with elements diffusion, but too high bonding parameters can cause grain seriously coarsening and reduce joint performance. The optimized process parameters of 1130 °C −60 min-10 μm Ni were obtained with reaching the highest shear strength of 656 MPa, which is the 201% of the direct diffusion bonded joint.