Modelling of the Stress Corrosion Cracking Behaviour for Low Alloy Steels in High Temperature Water

The goal of the model is to calculate the crack growth and to determine the parameters of relevance for the stress corrosion cracking of the low alloy steels in high temperature water for reactor safety purposes. The model assumes for the crack growth mechanism an anodic dissolution initiated by the rupture of the oxide film by creep at the crack tip, a repassivation, and, for representing other possible crack growth mechanisms, a cleavage. The model for the dissolution considers all the parameters of relevance for the dissolution and well accepted laws of physics. The creep is calculated by a constitutive law of Chaboche with the finite element method. The dissolution cell is found to be situated in the region of the crack tip with a length up to a few hundred micrometers. Sensitive parameters for the crack growth are the strain to film rupture, the composition of the electrolyte, the exchange current densities, and the cleavage length. The model is in qualitative agreement with measurements. It is discussed with particular attention to the geometry and dimensions of the dissolution cell and to the species transport in the dissolution cell and along the crack. Further work should be devoted to the comparison of the model to experiments. (author)