Laser Directed Energy Deposition of Inconel625 to Ti6Al4V Heterostructure via Nonlinear Gradient Transition Interlayers

Heterostructure (HS) refers to a class of structural materials composed of two or more different chemical components or crystal structures. Integration of Inconel 625 (IN625) nickel-based superalloy and Ti6Al4V (TC4) titanium alloy to a HS material offers a promising strategy to achieve graded thermo-mechanical properties, extended service temperature ranges, and significant weight reduction, which are highly desirable in aerospace applications. However, obtaining a better metallurgical bonding between the two alloys remains a critical challenge. In this study, laser directed energy deposition (L-DED) technology was employed to fabricate IN625/TC4 HS materials with a nonlinear gradient transition, following systematic investigations into the phase composition and crack sensitivity of IN625/TC4 gradient layers prepared from mixed powders of varying compositions. In addition, microstructure, phase distribution, and mechanical properties of HS materials at room temperature were characterized. The metallurgical defect-free IN625/TC4 HS material was successfully prepared, featuring a smooth transition of microstructure, reduced cracking sensitivity, and reliable metallurgical bonding. Furthermore, a novel design concept and illustrative reference for the L-DED fabrication of N625/TC4 HS material with excellent comprehensive performance was presented, while providing a theoretical metallurgical basis and data support for the potential applications of IN625/TC4 HS materials in the field of aerospace.