High-temperature oxidation performance of wire-arc additively manufactured Inconel 718 superalloys

Abstract

This work investigated the high-temperature oxidation kinetics and evolution of oxide phases of as-fabricated (AF) and heat-treated (HT) Inconel 718 alloys in air fabricated by the wire-arc additive manufacturing process. The results showed that the oxidation kinetics of all samples followed the parabolic time dependence. The microstructural study revealed the formation of very similar oxide scales in both AF and HT conditions. The oxide surface was found to be a mixture of complex spinel-MnCr₂O₄ and rutile-TiO₂ phases. The cross-sectional view yielded an outer layer of protective Cr₂O₃ scale, an inner layer of Nb-rich Ti_0.67Nb_1.33O₄ oxide and discretely formed internal Al₂O₃ oxides. The mechanism of scale formation is suggested on the basis of thermodynamic and kinetic abilities of cationic species.