High temperature oxidation of Ni-20Cr-12.5Al coatings containing 1% dispersed oxides

Oxidation studies were conducted on plasma sprayed coatings of Ni-20Cr-12.5Al containing one of the following: 1% MgO, 1% La₂O₃, 1% Y₂O₃, and 0.8% Y. The alloy powders containing dispersed oxides were prepared by a variety of processes employing attrition and ball milling. The TEM characterization of the plasma sprayed deposits of Ni-20Cr-12.5Al-1Y₂O₃ indicated that the oxide particles ranged from almost pure aluminum oxide to various compounds of aluminum and yttrium oxide. In cyclic tests conducted at 1150 and 1225°C, the coating containing 1% Y₂O₃ appeared to provide the best oxidation resistance. The oxidation resistance appeared to be influenced by the size and distribution of the oxide particles.