Factors influencing the service-like thermomechanical fatigue test cycle endurance of 1% CrMoV rotor steel

Service-like thermomechanical fatigue tests have been performed in order to characterize the endurance of 1 % CrMoV rotor steel under such transient thermal conditions. The key features of these tests are low strain rates(≤10 - 5 s - 1 ) and longer hold periods. In all testpieces, ratcheting with progressive section reduction is observed in the central portion of the gauge length accompanied by local amplification of the strain range. The finite-element-based analysis of this phenomenon allows the measured endurances to be rationalized with those determined from isothermal tests. Post-test inspection has revealed the development of two concurrent damaging mechanisms in the testpieces: (i) fatigue at the surface and (ii) creep in the interior. Different methods of damage calculation for creep-fatigue interaction are applied and compared in their predictive capabilities.