Inconel 718-CoCrMo bimetallic structures through directed energy deposition-based additive manufacturing

Abstract

Bimetallic structures and coatings through additive manufacturing (AM) have demonstrated a high degree of freedom for tailoring properties depending on the application. In this study, Inconel 718 and CoCrMo were used as both are common alloys and exhibit unique properties, such as high-temperature oxidation, wear, and fatigue resistance. Using directed energy deposition-based metal AM, bimetallic structures containing these two alloys were manufactured, and the resulting structures exhibited no intermetallic phase formation, cracking, or porosity. Scanning electron microscopy and energy dispersive spectroscopy revealed a smooth elemental transition between the two compositions. Hardness testing showed a linear transition in the interfacial zone, validating no brittle intermetallic phase formation. Compression testing and fracture surface analysis revealed that the failures were not dependent on the interface properties. High-temperature oxidation showed no distinct effect on the interface, a firmly attached chromium oxide layer on the Inconel 718 side and a loosely attached chromium oxide layer on the CoCrMo side. There was also evidence of pit formation on the Inconel 718 surface, but not on the CoCrMo. These findings confirm a stable bimetallic system in which one of the two alloys can be used on the other material to improve the structure’s high-temperature oxidation or wear/corrosion resistance.