Dr.-Ing, Linde AG, Höllriegelskreuth,
Dr.-Ing, Institut für Werkstoffkunde I, Universität Karlsruhe (TH), Karlsruhe,
Prof. Dr.-Ing, Institut für Werkstoffkunde I, Universität Karlsruhe (TH), Karlsruhe,
Prof. Dr.rer.nat Dr.-Ing. E.h.mult., Institut für Werkstoffkunde I, Universität Karlsruhe (TH), Karlsruhe,
Pages: 15 Published: Jan 2000
In total strain controlled in-phase and out-of-phase thermo-mechanical fatigue (TMF) tests on NiCr22Co12Mo9 (Inconel 617, Nicrofer 5520 Co) with a maximum temperature of 1123 K, a minimum temperature of 473 K and different mechanical strain amplitudes the cyclic stress-strain response, the change of the microstructure and the development of damage were analysed. The initial values of the induced stress amplitudes and plastic strain amplitudes, and the amount of cyclic hardening increase with the total mechanical strain amplitude. The observed cyclic hardening results from strong dislocation-dislocation and dislocation-particle interactions during plastic deformation at lower temperatures the latter being enhanced by the precipitation of small semi-coherent carbides at elevated temperatures of the TMF cycles. For each type of TMF tests the lifetime behaviour can be adequately described by the combination of the relationships of Basquin and Coffin-Manson. At equal total mechanical strain amplitudes in-phase tests always yield smaller lifetimes than out-of-phase tests. The difference between the two types of TMF-tests rises with increasing lifetime. This behaviour is caused by different accumulation of creep damage which is favoured by tensile stresses at high temperatures.
nickel-base superalloy, thermo-mechanical fatigue, cyclic deformation behaviour, damage development, lifetime behaviour
Paper ID: STP15252S