Creep and Fatigue Interaction Characteristics of PWA1484

One of the main methods for predicting the service life of jet engine turbine blades is through creep analysis. A sample of the turbine blade material will be mechanically tested to characterize its creep performance. This characterization will be used to determine safe operating conditions for the material. While methods for modeling creep behavior are generally well developed, this constant load creep testing does not fully represent the loading conditions present in a jet engine due to cyclic loading caused by the mission profile and throttle movements. As the industry seeks to become more accurate in physics based modeling of materials that are used in turbine blades, incorporation of these cyclic loads into the characterization of turbine blade materials is needed. It will be important to understand what effect pre-existing creep will have on fatigue life and what effect pre-existing fatigue loading will have on creep life. This research gives microstructural observations as well as data analysis of samples of PWA1484 tested at 871-C in creep-fatigue environment. This research resulted in the conclusion that prior fatigue cycling results in a non-linear reduction in the amount of primary creep, and an earlier transition to tertiary creep in PWA1484.