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) C9-217 - C9-230
DOI http://dx.doi.org/10.1051/jp4:1993920

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) C9-217-C9-230

DOI: 10.1051/jp4:1993920

The reactive element effect (REE) in oxidation of alloys

Yasutoshi Saito1, 2, Bülent Önay3, 2 and Toshio Maruyama4

1  National Institution for Academic Degrees, 4259 Nagatsuta-cho, Midori-ku, Yokohama 227, Japan
2  Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo 152, Japan.
3  High Temperature Materials Section, 2nd Materials Department, Hitachi Research Laboratory, Hitachi Ltd., 3-1-1 Saiwai-cho, Hitachi-shi, Ibaraki-ken 317, Japan
4  Department of Metallurgical Engineering, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo 152, Japan


Abstract
The reactive element effect (REE) in high temperature oxidation is discussed, for chromia-forming alloys, in terms of a mechanistic model based on postulations that (a) reactive element/oxide additions promote nucleation of Cr2O3 and (b) reactive element-oxides react with Cr2O3 to form perovskite-type compounds, such as YCrO3, along scale boundaries which promote inward oxygen diffusion. The standard Gibbs energy of formation and concentrations of ionic defects for YCrO3 are calculated. For silicon-containing chromia-forming alloys, the degradation of the scale adherence is shown to be the result of the α-β phase transformation in cristobalite. Morphologies of alumina scales formed over yttrium-containing Fe-20Cr-4Al alloys indicated that yttrium increased the stability of metastable alumina phases at 1173 K and decreased the amount of wrinkling in the α-alumina scale at 1273 K.



© EDP Sciences 1993