The development of new bond coat compositions for thermal barrier coating systems operating under industrial gas turbine conditions

► A range of Ni-Cr-Al-Co coatings have been produced using magnetron co-sputtering from Ni-Co-Cr and Al targets. ► Oxide composition map produced for NiCrAl alloys at 950 °C, with proposed boundaries for protective alumina scale formation. ► For the NiCrAl system, the critical levels of Al needed to form alumina were identified. ► Higher levels of non-protective oxides, such as NiO, CoO or spinels, were found on Co-rich coatings. ► The coatings that give the lowest oxidation rates were: 14 at.% Ni-8Co-18Cr-60Al; 31Ni-8Cr-61Al; and, 17Ni-22Cr-61Al.