Laser melting deposition of Inconel625 to Ti6Al4V bimetallic structure via vanadium interlayer

Inconel 625 (IN625) nickel-based high-temperature alloy and Ti6Al4V (TC4) titanium alloy are widely used in the aerospace industry due to their respective excellent properties. Developing the IN625/TC4 bimetallic structure (BS) has more apparent benefits and broader application prospects. Still, it has been challenging for industry research to connect these two materials successfully. In this study, IN625/TC4 BS without metallurgical defects such as cracks was successfully fabricated by adding the V interlayer using laser melting deposition (LMD) technique, and its microstructure and mechanical properties were investigated. The results indicate that IN625/TC4 BS can be divided into five regions from the IN625 side to the TC4 side, namely IN625 region, IN625/V transition region, rich V region, V/TC4 transition region, and TC4 region. The phase evolution of the five regions is as follows: γ-Ni + laves → γ-Ni + (Ni2Cr)V + TiNi3 + (V, Cr, Ni) solid solution → (V, Cr, Mo) solid solution + TiNi → β-Ti + TiNi + Ti2Ni → α-Ti + β-Ti. The Vickers hardness in the transition region is not uniformly distributed, with the highest value reaching 955 HV. The tensile strength of IN625/TC4 BS via V interlayer is approximately 267.6 MPa. The fracture location is located at the interface between rich V region and V/TC4 transition region, and its fracture morphology displays features of a quasi-cleavage fracture.