Microstructural Conditions Contributing to Fatigue Variability in P/M Nickel-Base Superalloys (Preprint)

摘要

Variability in the fatigue behavior of two common nickel-base superalloys is discussed, with emphasis given to understanding the behavior of short fatigue cracks. Rene88DT and IN100 are the materials of interest. and serve important roles in many turbine engine systems. Multiple specimens of each material were tested under low cycle fatigue (LCF) conditions at elevated temperature. Two IN100 specimens that exhibited significant difference in cycles to failure and three Rene88DT specimens having dissimilar short fatigue crack growth rates were interrogated to determine the reasons for these variation. This paper will discuss the microstructure adjacent to the initiation sites in these specimens and its role in affecting the observed disparate crack growth behavior. Additionally, an image correlation technique, use to evaluate the development of strain concentrations in a Rene88DT tensile specimen at room temperature, is described. The utility of image correlation for identifying microstructural 'hot spots' (i.e., initiation sites) in concert with LCF testing is considered.