Comparison of fatigue crack propagation in nickel base superalloys RR1000 and Udimet 720Li

The effects of temperature, dwell and environment on the fatigue crack growth behaviour of two nickel base turbine disc superalloys RR1000 and Udimet 720Li are presented in the present paper. Fatigue tests were carried out at room temperature in air using a 20 Hz sinusoidal loading waveform and at elevated temperatures of 650 and 725°C in both air and vacuum environments using a trapezoidal loading waveform with dwell times at a maximum load of 1 or 20 s. The fatigue crack propagation resistance of both materials is rationalised in terms of the influence of microstructure as well as the effects of alloy chemistry.