Oxidation resistance of NiCoCrAlTaY coated and uncoated Mar-M247 superalloys were compared experimentally in the air at 1150 A degrees C. It was found that the oxidation behavior of the NiCoCrAlTaY coated and uncoated Mar-M247 superalloys generally followed the parabolic kinetics with the rate of 1.5 and 9.8 x 10(-3) mg(2)/cm(4) h for each one. Microstructural observation and elemental analysis indicated that after 200 h the uncoated alloy covered with an oxide scale of 6-10 times thicker than the coated one, beneath which a fairly continuous and relatively thin alpha-Al(2)O(3) could be found along the interface close to the substrate. Comparatively, the NiCoCrAlTaY coated alloy uniformly produced the continuous, dense and thick alpha-Al(2)O(3) layer adhesive to the coating to prevent the metal elements against excessive oxidation, and finally formed the steady oxide scales: outer (Ni, Co)(Al, Cr)(2)O(4) spinels, NiO, (Al, Cr)(2)Ni(3); inner protective alpha-Al(2)O(3) with a little Cr(2)O(3). On the surface of the uncoated alloy, however, it mainly formed the Ni-rich oxides in which a large quantity of cracks propagated to result in the more oxidation.