Subsurface characterization of an oxidation-induced phase transformation and twinning in nickel-based superalloy exposed to oxy-combustion environments

►Oxidation products of Ni-based superalloy were studied in oxy-fuel combustion conditions. ► An oxidation-induced phase transformation occurred in the subsurface region. ► One of the two product phases was not in the Ni database of Thermo-Calc. ► This unknown phase is an ordered derivative of FCC structure of Ni-Ti(-Ta) system. ► This phase is likely detrimental to the mechanical integrity of the alloy in use.