Effect of Microstructure on the Fatigue Crack Growth Resistance of Nickel Base Superalloys

摘要

The objective of this study is to determine the effect of microstructural properties on the fatigue crack propagation (FCP) response of nickel base superalloys. This report describes the results of four experimental alloys containing various amounts of aluminum, titanium, and molybdenum. Chemistry, precipitate size, and grain size were varied to produce systematically controlled microstructures. The four alloys were characterized for chemical composition, microstructure, tensile properties, low cycle fatigue (LCF), and FCP resistance. The FCP tests were performed under constant load (increasing K) conditions in air at a stress ratio (R) of 0.1 and 0.8. Closure loads were measured with a clip gage, back-face strain gage, and a laser extensometer.