A Role of Texture in Controlling Oxidation and Hydrogen Ingress in Zr-Nb Pressure Tubes

Abstract

A nano-scale microstructural computer model for predicting ZrO₂ structure and texture development during oxidation of Zr-Nb alloy has been proposed. The model assumes that the main driving force for texture formation in oxide and growth of the oxide grains is the compression stress parallel to the oxide surface. The orientation of substrate grains also plays an important role. The oxide texture, microstructure, grain boundary character distribution and the stress development can be simulated. The substrate texture, microstructure, phase composition are the major factors determining the oxide structure. This structure controls the oxygen and hydrogen transport through oxide layer; therefore the model that predicts the oxide structure allows the simulation of the corrosion behaviour and hydrogen ingress through the oxide. The proposed model has been used to predict the Zr oxidation kinetics in air for different textures of the substrate. The result of simulation agrees with character of changes observed in oxidation experiments. Eventually, this model will be able to simulate the hydrogen ingress process and to predict hydride formation and cracking of the pressure tube. The comparison between the simulation and experimental results will be presented.