High temperature oxidation behavior of aluminized Haynes 230

•Reactive air aluminizing improved the oxidation resistance of H230 superalloy.•A three-zone microstructure observed in the diffusion coating on H230 superalloy.•Alumina growth due to phase transformation of β-NiAl to γ'-Ni3Al during Oxidation. The effect of reactive air aluminizing (RAA) on the high temperature oxidation behavior of the H230 superalloy is studied at 850 °C for 600 h. Mass gain values are measured and microstructure is studied by XRD, SEM, and EDX. Post oxidation mass gain for the aluminized H230 is reduced compared to wrought H230. The RAA process lead to formation of a three-zone diffusion coating with dominant β-NiAl in the two outer zones and increased γ'-Ni3Al after high temperature oxidation, which is attributed to the alumina scale growth during the high temperature oxidation.