Additive manufacturing of Inconel 718 – Ti6Al4V bimetallic structures

Abstract

Bimetallic structures belong to a class of multi-material structures, and they potentially offer unique solutions to many engineering problems. In this work, bimetallic structures of Inconel 718 and Ti6Al4V (Ti64) alloys were processed using laser engineered net shaping (LENS™). During LENS™ processing, three build strategies were attempted: direct deposition, compositional gradation and use of an intermediate bond layer. Inconel 718 and Ti64 alloys exhibit thermal properties mismatch along with brittle intermetallic phase formation at the interface resulting in delamination. For a successful build, the use of a compositional bond layer (CBL) was employed, which was a mixture of a third material - Vanadium Carbide - with the parent alloys to form an intermediate layer used in bonding the two immiscible alloys. A crack-free bimetallic structure of Inconel 718 and Ti64 was demonstrated. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction and Vickers hardness were used to characterize these bimetallic structures. XRD analysis indicated presence of Cr3C2 phases. CBL improved the bonding strength by avoiding formation of brittle intermetallic phases such as TiNi3 and Ti2Ni as well as reducing thermal stresses at the interface. Our results successfully demonstrate the formation of Inconel 718 and Ti64 bimetallic structures using a laser-based commercially available additive manufacturing approach.