Rechnerische Beschreibung der Verformung und Schädigung von Werkstoffen für Hochtemperatur-Dampfturbinen bis 720°C

The development of highest efficiency fossil power plants has become top priority. Within the German research project COORETEC DT3 the material behavior of large Nickel base components was investigated and subsequently modeled with advanced phenomenological methods as well as with constitutive models. Within this project amongst others the forged material Alloy 617F and the cast material Alloy 625C were tested at application-typical load levels. The experimental results were modeled using explicit equation and differential equation based models. The creep deformation and relaxation can be well reproduced using both approaches. Isothermal cyclic plasticity can be well reproduced using the differential equation based CNOW-model. The description of non-isothermal cyclic plasticity is not good. Obviously mechanisms not considered in the model act here. The prediction of fatigue life using the time- and temperature dependent damage parameter DTMF is successful. With these models a good set of tools is available. These can be used to predict lifetime of high temperature steam turbines up to 720 °C