Influence of alloying additions on the oxidation behaviour of zircaloy-2, Zr-2.5Nb and Zr-0.5Nb-1Cr in the temperature range 400-1200degC

Comparative assessment of the oxidation behaviour of three zirconium alloys has been done on the basis of kinetics of oxidation in steam at temperatures between 400 and 1200degC. Structural analysis of oxide films indicated that the films were predominantly monoclinic. Relative amounts of stresses in the films as estimated from peak shifts in XRD patterns showed that the films were stress free at 1200degC while at lower temperatures the stress was of the order 5 x 105 psi. Micro graphic examination of the cross-sections of oxidized samples was carried out using colour micrography and showed a difference in the morphology of the alpha layer in zircaloy on one hand and Nb-containing alloys on the other. The elemental redistribution due to oxidation was markedly seen at 1200degC. The difference in oxidation behaviour of the alloys has been explained. (author). 21 refs., 2 tabs., 6 figs