Effects of building orientation on the microstructure and high-temperature oxidation behavior of LPBF-processed Inconel 625 superalloy

The effects of building orientation (0°, 45°, 90°) on the microstructure and high-temperature oxidation behavior of laser powder bed fusion processed Inconel 625 (IN625) superalloy were studied in 1 atm O 2 at 900-1100℃. The results demonstrate no positive correlation between oxidation resistance and either grain boundary density or dislocation density in the as-fabricated Inconel 625 alloy. Conversely, the superior oxidation resistance observed in the 45° samples across all temperatures is attributed to the reduced dendritic structure, a deviation in preferred grain orientation to <101> and <111>, and an increased fraction of high-angle grain boundaries (HAGBs). After oxidation, δ-Ni 3 (Nb, Mo) phases precipitate on the subsurface of the alloy at 900-1000 ℃. At 1100 ℃, however, oxidation of δ-Ni 3 (Nb, Mo) led to the formation of NbCrO 4 at the oxide/alloy interface.