Creep-fatigue interaction model for crack growth of nickel-based superalloys with high temperature dwell time

A three-term crack growth model was developed by adding a creep-fatigue interaction term to the traditional linear superposition law. It is based on the hypothesis that the maximal creep-fatigue interaction occurs when creep and fatigue crack growth rates are comparable. Thereby a novel exponential form of interaction intensity factor was proposed. In order to verify the model, the creep-fatigue crack growth behaviour of a nickel-based powder metallurgy superalloy (FGH97) was experimentally investigated. Creep-fatigue crack growth rates were obtained at 750 °C with various dwell times. Comparison of the crack growth rates between fitted and measured values at 0s, 90s, 450s and 1500s dwell times show great agreement. Encouragingly, excellent predictive ability of the model was verified by the experiment at 25s dwell time. Furthermore, to test the applicability of the interaction law on other materials, experimental data of two additional superalloys from references, namely Alloy 718 and Hastelloy^® X, were used to fit the model. The results are also satisfactory.