Bonding temperature effects on the wide gap transient liquid phase bonding of Inconel 718 using BNi-2 paste filler metal

Abstract Transient liquid phase (TLP) bonding of Inconel 718 with BNi-2 filler metal has traditionally been carried out using thin filler metal (narrow gap) to achieve complete eutectic-free isothermal solidification layer joints. However, for the aerospace components with relatively large cracks or worn areas where a large amount of filler metal is needed, narrow gap TLP bonding is insatiable to meet the bonding requirements. In this paper, wide gap TLP bonding of Inconel 718 with the BNi-2 paste filler metal was carried out in a vacuum furnace. The bonding temperature effects on the interfacial microstructure, phase evolution and the mechanical properties of the bonded joints were investigated. It was found that the ultimate tensile bonding strength increased by 98% as the bonding temperature increased from 1015 °C to 1150 °C and the joint with the maximum tensile strength of 482 MPa was achieved after bonding at 1150 °C for 15 mins. However, more adverse heating was induced on the base metal of the joint under a higher bonding temperature. In addition, increasing bonding temperature from 1015 °C to 1150 °C improved the local plasticity of the bonded joints owing to the reduction of the homogeneously distributed Ni3B type borides to a more heterogeneous distribution of borides.