Optimizing multi-interlayered additive manufacturing for high strength robust joints in Inconel 718 and Ti–6Al–4V alloys

The fabrication of a robust joint of Ti–6Al–4V and Inconel 718 is indispensable for numerous industries including aerospace, space, and biomedical industries, and to date not achieved without intermetallic compounds (IMCs) and microcracks. In this study, the additive manufacturing of a dissimilar functionally graded joint of Ti–6Al–4V and Inconel 718 alloy was achieved by employing V, Cr, and Ni multi-interlayers. Interlayer materials were carefully selected to mitigate the limitations of brittle IMC formation. Microstructure characterization, EBSD, and elemental analysis confirmed that all joints of Ti–6Al–4V/V, V/Cr, Cr/Ni, and Ni/Inconel 718 were crack and IMC-free, despite substantial elemental diffusion throughout the fabrication route. The as-built specimen exhibited a tensile strength of 210 MPa, which increased to 250 MPa after stress-relief heat treatment and is 40% higher than the reported tensile strength of 150 MPa for a laser welded Ti–6Al–4V/Inconel 718 specimen. The maximum hardness of the entire fabrication was 380 VHN, a typical solid-solution hardness value, indicating no detrimental brittle IMC formation. Furthermore, the finite elemental analysis predicted a moderate stress level of 90 MPa at the interface, indicating robust fabrication.