Mechanisms of the Texture Influence on the Corrosion Behavior of Zr-Alloy Cladding Tubes

摘要

Different mechanisms of how the crystallographic texture affects the corrosion behavior of the cladding tubes made of commercial Zr-based alloys are considered under service conditions. It is shown that the dependence of corrosion resistance of the tubes on the degree of recrystallization correlates with the distribution of prismatic axes in the tube texture, which can be regarded as an indicator of the propensity of the tube to intergranular oxygen diffusion. The effect of the layerwise inhomogeneity of a texture on tensile stresses is studied in the surface layers of the tube. It is shown that tensile stresses enhance oxygen diffusion into internal layers of the tube. It is established that, under the action of tensile stresses arising during oxide formation in the surface layer, twinning of the a-Zr matrix takes place near the front of oxidation. The texture of the monoclinic phase of the oxide layer is stable under tube surface treatment owing to existence of the orientation relationship with the substrate.