Tensile-hold low-cycle-fatigue properties of solid-solution-strengthened superalloys at elevated temperatures

Total strain-controlled low-cycle-fatigue (LCF) tests on three solid-solution-strengthened superalloys, HAYNES 188, HAYNES 230, and HASTELLOY X, were carried out at temperatures ranging from 816 °C to 982 °C in laboratory air. Various hold times were introduced at the maximum strain to investigate the high-temperature fatigue and creep-fatigue interactions. The cyclic-stress response and fatigue life of three superalloys were compared. It was found that the fatigue life of three superalloys was dependent on the imposed total strain range, the duration of hold time, and the test temperature. The different fatigue-life behavior indicated by three superalloys appeared to be related to the difference in the damages from creep and oxidation. Several material properties for three superalloys were obtained using the Holloman and Coffin-Manson relations. The fracture surfaces and metallographic sections of the fatigued specimens were observed to determine the crack initiation and propagation modes.