The Microstructure and Mechanical Properties of a Dissimilar Rotary Friction Welded TC4 Titanium Alloy to 304SS Stainless Steel with Inconel 718 Alloy Interlayer

This study investigates the microstructure and mechanical properties of a dissimilar joint formed by rotary friction welding, which joins TC4 titanium alloy to 304 stainless steel using an Inconel 718 interlayer. The welding parameters were as follows: a friction time of 9 s, a friction pressure of 160 MPa, an upset time of 2 s, a forging pressure of 250 MPa, and a rotational speed of 1400 rpm. Microstructural analysis revealed the formation of intermetallic compounds (IMCs), including Fe2Ti, Ni3Ti, NiCrFe, FeNi3, Ti2Ni, and FeNi, at the TC4/Inconel 718 interface, while Ni3Ti and FeNi3 IMCs were identified at the Inconel 718/304SS interface. The tensile tests demonstrated that the joint with the Inconel 718 interlayer (TC4/Inconel 718/304SS) achieved an ultimate tensile strength (UTS) of 717.73 MPa and an elongation of 13.05%. In contrast, the direct joint without the interlayer (TC4/304SS) exhibited a lower UTS of 631.58 MPa and a reduced elongation of 7.39%. Therefore, the introduction of the Inconel 718 interlayer significantly improved joint quality, increasing tensile strength by 13.64% and elongation by 76.59%. More importantly, the interlayer effectively inhibited the formation of brittle Ti-Fe intermetallic compounds, which are typically detrimental to joint performance.