Microstructural characterisation and high-temperature oxidation of laser powder bed fusion processed Inconel 625

•Heat-treated IN625 shows a recrystallised microstructure, similar to wrought IN625.•Detailed analysis of the oxidation data demonstrated cubic oxidation kinetics.•A Cr2O3 scale formed with a near-continuous δ-phase layer underneath.•Suggested that the cubic behaviour was caused by the formation of the δ-phase layer. Oxidation of Laser Powder Bed Fused (L-PBF) IN625 was studied in the as-built and heat-treated conditions. Following heat treatment, recrystallisation was observed with a large fraction of twin grain boundaries, and Nb-rich carbides decorated grain boundaries. Samples of L-PBF IN625 were exposed at 950 °C in laboratory air and pressure for up to 504 h. An external chromia scale was formed, alongside a near-continuous δ-phase layer at the scale/alloy boundary. The kinetics of oxidation were similar to wrought IN625, but more closely followed cubic behaviour. It is suggested that the cubic behaviour was caused by the formation of the δ-phase layer.