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Evaluation of time dependent thermomechanical fatigue crack growth in a nickel alloy for power plant applications

: Schlesinger, M.; Schweizer, C.; Brontfeyn, Y.; Charkaluk, E.

Beck, Tilmann ; Deutscher Verband für Materialforschung und -prüfung e.V. -DVM-, Berlin; American Society for Testing and Materials -ASTM-, Philadelphia/Pa.:
Seventh International Conference on Low Cycle Fatigue, LCF 2013 : September 9-11, 2013, Aachen, Germany
Berlin: DVM, 2013
ISBN: 978-3-9814516-2-7
International Conference on Low Cycle Fatigue (LCF) <7, 2013, Aachen>
Fraunhofer IWM ()
damage mechanisms; fatigue crack growth; microstructure evolution; nickel-based superalloys; thermomechanical fatigue

In the present study fatigue crack growth rates were measured under isothermal and nonisothermal conditions up to 700 °C for the nickel base material alloy 617. The microstructure and mechanical properties of alloy 617 are influenced by the thermal heat treatment and the following thermal exposure in service. Hence, a solution annealed and a long-time service exposed material were studied. The service exposed material was extracted from the component test plant, which was operated for a time of about 20.000 hours within the EUproject COMTES700 whereof 13.000 h were at a temperature above 680°C. The measured fatigue crack growth rates results in a function of material condition, temperature and load waveform. Furthermore, the results of the non-isothermal tests depend on the phase between thermal and mechanical load (in-phase, out-of-phase). A fracture mechanic based, time dependent model is upgraded by an approach to consider environmental effects, where almost all model parameters represent directly measureable values. A consistent description of all results and a good correlation with the experimental data is achieved.