Zum thèrmisch-mechanischen Ermüdungsverhalten von NiCr22Co12Mo9

On the Thermal-Mechanical Fatigue Behaviour of NiCr22Co12Mo9 The fatigue behaviour of the Ni-based alloy NiCr22Co12Mo9 (corresponding to Inconel 617) under combined cyclic thermal and mechanical “in-phase”- and “out-of-phase”-loading was investigated with a constant minimum cycle temperature of 473K and a constant total strain amplitude of 6,25% at maximum cycle temperatures T_o ranging from 873K to 1473K. It was found that the cyclic deformation behaviour and the corresponding development of the microstructure during the tests were mainly determined by the maximum cycle temperatures. With increasing T_o increasing recovery processes occurred accompanied by charakteristic changes in the microstructure which reduced cyclic hardening. In contrast, both maximum cycle temperature and cycle mode determined surface deteriorations, which were characterized by surface cracks, and fatigue life. At the highest temperatures during the in-phase-loading cycles, the occuring tensile stresses caused increasing amounts of intergranular damage with corresponding reductions of fatigue life.