Effect of Cycle History on Thermomechanical Fatigue Response of Nickel-Base Superalloys

Thermo-mechanical fatigue of nickel-base superalloys has been carried out for more than twenty years, but a unified standard for such tests has yet to be fully formulated. As a consequence of this, even excluding differences in testing procedure from laboratory to laboratory, the range of testing conditions in use is very large. In this paper, the authors consider the effect of the different parameters in a TMF test such as hold-time and temperature-mechanical phase angle on the thermo-mechanical response of test samples. This is carried out in terms of both stress response and sample life, in order to identify the common trends in the sample damage during the evolution of the mechanical response. To date, no definitive test program systematically covering the different variables has been published in the scientific literature. As, even after a long span of time, the literature data for many alloys is sparse, the work presented here concentrates on analyzing TMF response data from test programs carried out by the authors on the single crystal nickel-base alloy SRR99. [S0094-4289(00)01003-3]