Numerical modelling of the microstructure effect on fatigue behaviour of Ni-base superalloys for turbine disk

Abstract : Nickel-based alloy like N18 can present various types of precipitate distributions according to the applied heat treatment. A model involving a three scale homogenization procedure is developed to characterize the influence of this microstructure on fatigue life. The microstructural parameters are the size and the volume fraction of the secondary and tertiary precipitates of gamma phase. Experimental results at 450 °C, specially designed to calibrate the model, allow to understand the role of tertiary precipitation. The first identification of the three scale homogenization model is shown.