Dissimilar joining of Ti3Al-based alloy to Ni-based superalloy by arc welding technology using gradient filler alloys

Abstract

Abstract In this study, Ti–Al–Nb, Ti–Ni–Nb and Ni–Cr–Nb system alloys were designed and incorporated in order to construct a gradient structure at the surface of the joined Ti3Al base material. And the Ti3Al-based alloy and Ni-based superalloy were successfully joined together using gas tungsten arc (GTA) welding technology. The microstructure evolution, mechanical properties and fractured behaviors of the joints were investigated. The gradient structure remarkably decreased the formation tendency of brittle phases within the joints compared with a single filler alloy and thus improved the joint strength effectively. The average room-temperature tensile strength of the Ti3Al/In718 dissimilar joint reached 353 MPa, and the strength value at 873 K was 245 MPa. At the Ti–Ni–Nb/Ni–Cr–Nb interface, some Ni3(Nb, Ti) + (Nb, Ti)Cr2 and TiNi3 phases were detected in the Ti–Ni–Nb matrix. It was believed that their presence decreased the room-temperature strength of the Ti–Ni–Nb alloy but improved its high-temperature strength.