The evolution of microstructure of hot-forged superalloy 718 can be tailored to specific customer demands by local adjustment of the overall metallic forming process. Further on, increased economic sustainability will continuously comply with the lightweight demands. Therefore it is necessary to incorporate the local fatigue behavior right during the design stage. The main output of hot-forging process simulation is defined by microstructural parameters like grain size, amount of δ-phase as well as γ '('')-precipitation contents, etc. The presented work shows the use of an alternative microstructural approach leading to two ancillary microstructural parameters called 'microstructural energy parameter e' and 'factor of heterogeneity b'. This newly developed microstructural evaluation model, which is based on interpretation of the cumulated shape of individual grains, supports an alternative characterization method of microstructure, encompassing morphological information in a combined manner. Based on the thoroughly used microstructural based energy approach it is possible to close the complex simulation chain between forging process simulation and fatigue. The developed method to assess a closed simulation loop at design stage is based on extensive fatigue tests and corresponding metallographic work. This leads to a parametric interface between the individual project tasks. The basic approach presented here establishes a common link between hot forging simulation codes and calculation of the component life time for superalloy 718.

Description of a forging process which relates the fatigue life to microstructure needs to take into account several influencing factors throughout the entire hot-forging process. The calculation of dynamic fatigue strength based on static properties for hotforged components of superalloy 718, especially at elevated temperatures, is in general not possible. The main objective of this paper is to present the capability of the 'Micro Structural Energy Approach' (MSEA), to determine the influence of different forging parameters on fatigue life, within a valid process window for aerospace components. This MSEA technique is based on extensive experimental data, and considers short-crack growth for damage assessment. The two parameters, viz. mean grain size and factor of heterogeneity, are used to link experimentally obtained life time results with its microstructure. These parameters are also capable of establishing a stable fatigue life prediction tool, by evaluation of the microstructure coupled with the hot-forging process simulation.