Model predictions of grain boundary chromium depletion in Inconel 690

Abstract A new three dimensional modelling technique has been developed to predict chromium depletion from grain boundaries in Ni–Cr–Fe alloys. The technique is based on precipitation kinetics represented by the Zener’s Equation and the error function solution of the diffusion law. Unlike former models, the model predicts a natural transition from sensitization to desensitisation and time delay in reaching the minimum chromium concentration at grain boundaries. In addition, the whole prediction can be made using a single Excel worksheet, therefore provides a simple and effective tool for sensitization/desensitisation predictions and studies. Grain size effects and temperature-time-concentration (TTC) maps can also be predicted. The model has been validated against experimental investigations reported in the literature on Inconel 690 aged at four temperatures for different time periods and good agreement between model predictions and experimental observations of chromium depletion has been achieved.