Actes du 3ème Colloque International sur la Corrosion et la Protection des Matériaux à Haute Température
J. Phys. IV France 03 (1993) C9-257-C9-264
Beneficial effects of Y2O3 dispersion on Al2O3 protective coatingY. Ikeda and M. Yata
National Research Institute for Metals, 1-2-1, Sengen, Tsukuba, 305, Japan
We have studied the mechanism by which dispersed Y2O3 exerts beneficial effects on the oxidation protection of an Al2O3 coating (film) on the basis of the following models : 1) Y2O3 suppresses surface segregation of S by trapping it in the alloy matrix and accordingly suppresses spalling of the Al2O3 film ; 2.1) The diffusion of alloying elements into the Al2O3 film is retarded by dispersed oxide particles, probably through formation of a diffusion barrier at the Al2O3/alloy interface ; 2.2) The diffusion in film is retarded through incorporation of Y2O3 into the film ; 3) Y2O3 acts as an adhesive at the Al2O3/alloy interface ; 4) Y2O3 incorporated into the film suppresses the spalling by increasing the plasticity of the film. We reached the following conclusions : 1 is very important, 2 is also significant but 3 and 4 are negligible.
© EDP Sciences 1993