Microstructural understanding of high-temperature oxidation behaviour of selective laser melted Inconel 718 superalloy in CO₂ atmosphere

In this work, the oxidation behavior of Inconel 718 superalloy fabricated by selective laser melting was investigated in the CO₂ atmosphere at 1000 and 1100 °C. Results show that the structure of the oxide scales is strongly dependent on the grain position (grain boundary and grain interior) and the oxidation temperature. It forms six-layer and four-layer oxide scales at the grain boundary region after 300 min oxidation at 1000 and 1100 °C, respectively, producing three-layer oxide scales in the intragranular area. The formation mechanisms of the oxide scale were discussed. Additionally, the Kirkendall voids and internal oxidation in the matrix preferentially form at 1100 °C.