Development of thermal fatigue damage in 1CrMoV rotor steel

Crack initiation endurances have been determined for a 1CrMoV rotor steel in uniaxial service cycle thermo-mechanical fatigue (TMF) tests formulated to simulate a range of steam turbine start cycles with a maximum temperature of 565 deg. C. The experimental details for these TMF tests are described. Post test inspection has been employed to characterise the associated thermal fatigue damage mechanisms for the steel which are observed to be dependent on the magnitude of the thermal transient in the TMF cycle. The lowest resistance to thermal fatigue damage development occurs in these tests when the conditions determine that the rate of creep damage accumulation below the surface exceeds the rate of fatigue crack development at the surface