Diffusion bonding of Zr-2.5Nb zirconium alloy and 304L stainless steel with Nb/Ni hybrid interlayer

•Nb/Ni hybrid interlayer was applied to join 304L SS and Zr-2.5Nb Zr alloy.•The diffusion area has significantly stratified structure.•Ni3Nb IMCs occurred in the Nb/Ni interface with high hardness. Diffusion bonding of Zr-2.5Nb zirconium alloy and 304L stainless steel with Nb and Ni hybrid interlayer was performed at 850-1050 ℃ under 4 MPa for 30 min. From 304L side to Zr-2.5Nb side, the typical interfacial structure of the 304L/Ni/Nb/Zr-2.5Nb joints was (Ni, Cr, Fe) solid solution/Ni/Ni3Nb IMCs/Nb/(Zr, Nb) solid solution. Of the five layers, the nano-hardness of Ni3Nb IMCs layer was the highest, reaching ∼9.22 GPa for the joint bonded at 1000 ℃. With the increase of bonding temperature, the shear strength of the joint increased first and then decreased, and the maximum strength of 84.4 MPa was obtained at 1000 ℃. For the joint bonded at 1000 ℃, the fracture location was between the residual Ni layer and Ni3Nb IMCs layer, and the fracture type was a mixture of brittle fracture and ductile fracture.