Fatigue Properties of Conventional and Hybrid Inconel 718 Brazed Joints with Nickel-Based Filler Metal Ni 660

Nickel-based superalloys such as Inconel 718 are widely used in aerospace and energy applications due to their high strength and excellent temperature resistance. In addition to conventional manufacturing methods such as casting and machining, additive manufacturing - particularly laser powder bed fusion - is gaining increasing importance. Combining conventional and additive manufacturing routes into hybrid components offers potential for greater design flexibility and material efficiency. A metallurgical joint between the individual parts can be achieved through brazing. However, the fatigue properties of such hybrid brazed joints have not been sufficiently investigated to date. In this study, both conventional and hybrid brazed joints made from Inconel 718 were produced using the nickel-based brazing alloy Ni 660. Brazing was carried out in a vacuum furnace at 1190 °C for 15 minutes. The fatigue behavior of the brazed joints was then characterized through fatigue testing. Across the entire load range, the conventional brazed joints exhibited higher fatigue strength compared to the hybrid ones. The inferior performance of the hybrid brazed joints can be attributed to the microstructure of the joining zone: while conventional brazed joints feature a continuous brittle phase band, the hybrid brazed joints contain two distinct brittle phase bands. These brittle phase bands govern the failure behavior of the hybrid brazed joints.Fabian Frittgen