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

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-MnCr 2 O 4 and rutile-TiO 2 phases. The cross-sectional view yielded an outer layer of protective Cr 2 O 3 scale, an inner layer of Nb-rich Ti 0.67 Nb 1.33 O 4 oxide and discretely formed internal Al 2 O 3 oxides. The mechanism of scale formation is suggested on the basis of thermodynamic and kinetic abilities of cationic species.