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Steels with various chromium contents are widely applied in steamturbine components and have been introduced steadily in the last decades. The initialaim in the development of such steels is to achieve high performance in creep resistance.Due to the fluctuations of electrical power demand nowadays, power plants areincreasingly forced to run at varying utilization levels, which can shift the critical loadto fatigue domain by superimposed creep on the heated surface of components. In thecurrent paper, the creep fatigue behavior of 1%-, 2%- and 10%Cr steels undermultiaxial loading is described. The experimental investigation was conducted on steelsof the types 1Cr-1Mo-Ni-V, 2Cr-1Mo-W-V and 10Cr-1Mo-1W-V-Nb-N asrepresentative samples for each of the three steel grades. The experimental databaseconsists of uniaxial as well as biaxial creep fatigue experiments which were conductedon a biaxial cruciform testing machine. Of special interest was a lifetime comparison ofexperiments under thermomechanical and isothermal loading at the maximumapplication temperature. A unified viscoplastic constitutive material model with anincorporated damage variable was applied for lifetime assessment. Finally,metallographic investigations contribute to a better knowledge of the evolution ofdamage and its modelling. The investigation shows slightly different effects on lifetime,dependent on the three steel grades.