In this work, the high temperature oxidation behavior of selected MCrAlY overlay coatings has been investigated using the elemental concentration pro. le analysis. Emphasis is placed upon the influence of chemical composition on the oxidation. The results show that the oxide scale formation on coatings is considerably influenced by the microstructure of coating, the chemical composition of M as well as CrAlY, and the interdiffusion from substrate. If an element exists only in the one side of the overlay coating system, the diffusion amount of that particular element becomes higher. The vacancies which formed near the substrate/coating interface after thermal exposure could be generated by the diffusion of Ni and Al. A seriously diffusion-affected zone between substrate and coating are observed within 80 mm from the substrate/coating interface toward the coating surface. The cobalt-including CoCrAlYs and CoNiCrAlYs outperform the nickel-based system under the high temperature oxidizing condition. (C) 2008 Elsevier B.V. All rights reserved.