Cyclic oxidation behaviour of as-deposited Ni-11·5Cr-4·5Co-0·5Al superalloy sheet when heated at 800°C

The excellent performance of superalloys is famous for their applications under high-temperature oxidation conditions. The grain size of the superalloy affects the morphology and the composition of the oxide scale. The cyclic oxidation characteristics up to 24 times of Ni-11·5Cr-4·5Co-0·5Al microcrystalline sheets, which are prepared by electron beam physical vapour deposition, were investigated at 800°C in air for 2 hours in this paper. The oxide scales were examined by scanning electron microscopy equipped with an energy-dispersive X-ray system. The oxide scales chemical phase was determined by glancing angle X-ray diffraction. The results showed that the oxide scales were mainly composed of alumina. The surface of the scale was rough and non-uniform with grey and bright zones at the fourth cycle. It became smooth, continuous and uniform at the 24th cycle.