High Temperatures Oxidation of Inconel 718 Superalloy Produced by Additive Manufacturing: Influence of Scanning Direction Strategy, Microstructure and Heat Treatment

LPBF is an additive manufacturing technique that allows the building of complex geometries. Its process parameters directly influence the microstructure of the material. Inconel 718 is a nickel-based superalloy with excellent mechanical properties and oxidation resistance at elevated temperatures. However, when built by AM, its anisotropic microstructural character can influence the oxidation resistance, impairing the mechanical integrity. This work investigates the effects of high temperature exposure on the LPBF IN718. Samples manufactured with two different scanning strategies and with and without age-hardening heat treatment were prepared in three different orientations: X, Y and Z, and subjected to oxidation tests at 1000 °C for 24 h in order to measure the mass variation and characterize their surfaces. Conventional forged samples were used for comparison. ANOVA, OM, SEM-EDS and XRD analyses showed a strong influence of both parameters on the oxidation of all faces. The samples produced using 0° angle had better performance compared to 67°, with less mass gain. Heat treatment promoted grain recrystallization, improving the resistance to oxidation in some cases. Faces X and Y presented similar mass gains at 0°, with better performance for non-treated samples. Face Z showed the lowest mass gain, with better performance for treated samples.