Charakterisierung der Rekristallisationsvorgänge in IN718 beim Hammerschmieden mittels Servotest-Versuchen

In order to optimize the production costs of manufacturing processes of structural aircraft parts out of a nickel-based superalloy, a shift of individual forming steps up to the entire production from screw presses to hammers would be beneficial. Unfortunately the results of the used microstructure model deviate significantly from the real grain size. This can be explained by the missing experimental support points for the sequential deformation and very high strain rates and thus inappropriate model parameter sets. As a result the microstructure simulation is strongly based on extrapolation. To correct this error, the structural changes of the nickel-based superalloy Inconel® 718 should be analyzed under the conditions as they exist in the hammer forging process in this master thesis. For this purpose a Servotest forming simulator is used to deform cylindrical upsetting samples of different pre-materials with varying temperatures and stroke sequences. Subsequently the samples are analyzed metallographically. Furthermore, the compression test are simulated in a finite element (FE) model, to derive a temperature, strain and strain rate history for each position of interest in the sample. The simulation results and the corresponding metallographic evaluations are intended to provide the previously mentioned necessary support points for the microstructure model.