The W-added 12%Cr ferritic heat resistant steel has been developed as a turbine rotor material which is used under high temperature creep-fatigue conditions. In this study, crack growth tests using C(T) specimen under the creep-fatigue interaction conditions were conducted under various conditions of stress holding time, applied stress and temperatures. As a result, the effect of load frequency on crack growth behaviour and its life for this steel was characterised by the three-dimensional curved surface based on the concept of non-equilibrium science. Furthermore, a predictive law of crack growth life under the creep-fatigue interaction conditions was derived based on the concept of Q∗with the transition function of crack growth life from fatigue to creep.
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