Corrosion behavior of wire arc additive manufactured Inconel 718 superalloy

The corrosion behavior of Inconel 718 (IN718) superalloy fabricated using wire-arc additive manufacturing (WAAM) and post-deposition heat treatment is investigated and compared to that of wrought alloy. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) analyses show that the corrosion resistance of heat-treated WAAM IN718 (WAAM-HT IN718) is inferior to that of heat-treated wrought alloy (wrought-HT). Potentiostatic polarization and X-ray photoelectron spectroscopy (XPS) are used to analyze passivation properties of the materials. The results indicate that in comparison to the wrought-HT material, the passive film formed on the WAAM-HT IN718 contains more NiO, which is porous and less protective than Cr2O3. The formation of more NiO and lesser Cr2O3 in the passive film formed on the WAAM-HT IN718 could be related to its {100} < 001 > (Cube) texture. Moreover, based on thermodynamic calculations, Nb depletion in its gamma matrix, due to selective partitioning of Nb into Laves phase and delta phase particles, can also contribute to formation of the porous passive film. (C) 2020 Elsevier B.V. All rights reserved.