Influence of a Ni Plating Surface Preparation on Transient Liquid Phase Bonding Behaviour of Inconel 718/BNi-2

The influence of a Ni plating surface treatment on transient liquid phase bonding (TLPB) of superalloys was investigated through a comparison of BNi-2 filler metal joints made with IN718 base metals (BM) with and without a Ni plating surface treatment. Interdiffusion between the BM and Ni plating occurred during initial heating, creating a compositional gradient at the faying surface. This resulted in the formation of a boride free denuded zone immediately below the BM faying surface. In parallel, the Ni plating acted as a diffusion barrier against the filler metal, preventing BM dissolution (BMD). The lack of BMD was accompanied by a reduced initial boron uptake by the BM and little gap widening in Ni-plated samples. The rate of IS was approximately the same regardless of surface preparation. Overall, the presence of a Ni plating reduced the time to complete isothermal solidification by approximately 25 pct, primarily due to the prevention of BMD and the associated gap widening.