Influence des contraintes de croissance sur l'oxydation du fer par la vapeur d'eau en symétrie cylindrique.
Résumé
A morphological comparative study of wüstite coating, obtained on pure iron plates and wires in water vapor, indicates the presence of overstresses in the case of cylindrical samples.
By associating these results with a kinetic comparative study, it has been shown that there is no change in the oxidation mechanism, but just some deviations occuring with time for cylindrical symmetry, when regulating processes (external boundary phase process, followed by diffusion) are perturbated by manifestations of stresses relaxation either at the oxide /gas boundary phase or/and in the diffusional volume. These differences, markedly increasing with temperature lowering, result in an activated phenomenon, the activation energy of which is close to that of iron self- diffusion in wüstite.