EDP Sciences Journals List
Issue J. Phys. IV France
Volume 03, Number C9, Décembre 1993
Proceedings of the 3rd International Symposium on High Temperature Corrosion and Protection of Materials
Actes du 3ème Colloque International sur la Corrosion et la Protection des Matériaux à Haute Température
Page(s) C9-551 - C9-557
DOI http://dx.doi.org/10.1051/jp4:1993958

Proceedings of the 3rd International Symposium on High Temperature Corrosion and Protection of Materials
Actes du 3ème Colloque International sur la Corrosion et la Protection des Matériaux à Haute Température

J. Phys. IV France 03 (1993) C9-551-C9-557

DOI: 10.1051/jp4:1993958

The effect of reactively-sputtered alumina films on the oxidation resistance of CoCrAlY coatings

Fuhui Wang, Shenglong Zhu, Hanyi Lou and Weitao Wu

Corrosion Science laboratory, Institute of Corrosion and Protection of Metals, Academia Sinica, Shenyang 110015, China


Abstract
Thin alumina films have found applications in electronic circuits and cutting tools and have been recently explored as protective coatings against high temperature oxidation, but these studies have been relatively rare. In this study, amorphous alumina films 3.5 µm thick were produced by reactive sputtering on Co-30Cr-6Al-0.5Y coatings, using a pure aluminum target in Ar + O2 atmosphere. Isothermal oxidation tests were carried out at 1000-1100 °C in static air. The results showed that the alumina films improved the oxidation resistance at all testing temperatures. At 1000°C, the Co-30Cr-6Al-0.5Y coating could form pure alumina scale on its surface, but the reactively-sputtered alumina films reduced the oxidation rate. At 1100 °C, the Co-30Cr-6Al-0.5Y coating could not form pure alumina scale, as a result of a severe internal oxidation of aluminum along the columnar defects. The scales were composed of Al2O3, Cr2O3 and TiO2, which were not so protective as pure alumina scales. On the contrary, the Co-30Cr- 6Al-0.5Y coatings with 3.5 µm preformed alumina films exhibited excellent oxidation resistance at 1100 °C. Only minor amounts of TiO2 were detected on the surface. Moreover, the reactively-sputtered alumina films were very adherent to the CoCrAlY coatings. At 1000 °C no spallation was found, while at 1100 °C only a little spallation produced during cooling was observed.



© EDP Sciences 1993