A Closed Concept to Associate the Hot-forging Process Controlled Microstructure with Fatigue Life

Abstract

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.