INFLUENCE OF ALLOYING ADDITIONS ON THE OXIDATION BEHAVIOR OF ZIRCALOY-2, ZR-2.5NB AND ZR-0.5NB-1CR IN THE TEMPERATURE-RANGE 400-1200-DEGREES-C

Comparative assessment of the oxidation behaviour of three zirconium a lloys has been done on the basis of kinetics of oxidation in steam at temperatures between 400 and 1200-degrees-C. Structural analysis of ox ide films indicated that the films were predominantly monoclinic. Rela tive amounts of stresses in the films as estimated from peak shifts in XRD patterns showed that the films were stress free at 1200-degrees-C while at lower temperatures the stress was of the order 5 x 10(5) psi . Micrographic examination of the cross-sections of oxidized samples w as carried out using colour micrography and showed a difference in the morphology of the alpha layer in Zircaloy on one hand and Nb-containi ng alloys on the other. The elemental redistribution due to oxidation was markedly seen at 1200-degrees-C. The difference in oxidation behav iour of the alloys has been explained.