On the fatigue crack propagation behavior of superalloys at intermediate temperatures

Two superalloys used in gas-turbine disks, Rene 95 and IN-100 were tested in several forms at 0.33 Hz in air, and the results were compared with earlier data on Astroloy to gain a better understanding of the effects of grain size, strength, and alloy composition on the fatigue crack propagation behavior. In addition, selected forms of Rene 95 were tested at 0.33 Hz in vacuum and in air using a cycle with a 120-sec tensile dwell to evaluate the effects of environment and creep. Results of the study emphasize the beneficial effect of large grain size on the fatigue and crep-fatigue crack growth resistance of the superalloys in the temperature range corresponding to the operating temperatures of aircraft gas-turbine engine disk rims.