Prediction Model of EAC Growth Rate of Nickel-based Alloy under Low Temperature and High Stress

One of the recognized quantitative calculation models of crack growth rate is the Ford and Andresen model for predicting the crack growth rate of environmentally assisted cracking (EAC) based on oxide film rupture theory. In the Ford-Andresen model, the crack tip strain rate is the core mechanical parameter needed to obtain the quantitative calculation of crack growth rate, but obtaining an accurate calculation is difficult. To obtain a more simplified quantitative model of environmental crack growth rate, the nickel-based alloy 600, a nickel-based alloy commonly used in structural material for nuclear power, was used as the research object, and its mechanical properties, low-temperature/high-stress creep curve, and creep rate were obtained in experiments. Based on the creep characteristics of alloy 600 under low temperature and high stress, a quantitative calculation of its creep rate was obtained. The creep rate can be used to replace the strain rate at the crack tip in the EAC growth rate prediction model, and a quantitative prediction model for the crack growth rate based on using the creep rate at the crack tip as the mechanical parameter can then be established, which simplifies the crack growth rate prediction model based on using the crack tip strain rate as a mechanical parameter. The relationship between stress and the stress intensity factor at the crack tip obtained by finite element simulation, as well as a quantitative calculation model of creep rate, is established, which is characterized by the stress intensity factor of the crack tip. Moreover, experiments establish a quantitative calculation model of creep rate characterized by stress at the crack tip so that different quantitative prediction models of crack growth rate characterized by crack tip creep rate can be established. Then the effect of the mechanical parameters, creep parameters, and electrochemical parameters of alloy 600 on the prediction model is analyzed, providing a basis for the application of the prediction model.