Article révisé par les pairs
Résumé : Ni-Co-ThO//2 composites prepared by a coprecipitation method have been studied under air oxidation conditions between 800 and 1000 degree C. Thermogravimetry showed slight but continuous oxidation of the material. The effect of 5-20% chromium powder additions to the base powder mixture was studied. The results demonstrated significant decreases in oxidation rate, starting from 10 wt. -% chromium addition while efficient protection was obtained from 15 wt. -% by formation of a Cr//2O//3 scale. Polarized light microscopy studies, as well as scanning electron microscopy, coupled with x-ray emission microanalysis and x-ray diffraction, enabled qualitative analysis of the different zones distinguished inside the oxide scale. This led to the establishment of an oxidation mechanism related to the chromium content.