Isothermal fatigue behavior of cast superalloy Inconel 792-5A at 23 and 900 °C

Total strain-controlled tests have been performed on cylindrical specimens of polycrystalline Inconel 792-5A at 23 and 900 °C to study the effect of temperature on low cycle fatigue characteristics and cyclic strain localization. Hardening/softening curves, cyclic stress–strain curves, and fatigue life curves are presented. Two linear dependencies are used to approximate the room temperature data in Manson–Coffin plot. Technique of oriented foils observed in transmission electron microscope is used to study dislocation structure. Effect of temperature on surface relief topography and fracture surface is documented using scanning electron microscopy and atomic force microscopy. High-amplitude straining is characterized by slight initial hardening followed by saturation at room temperature and sustained weak softening at 900 °C. Low-amplitude cycling results in the stable stress response. Plastic strain localization into persistent slip bands lying along {111} slip planes was observed at both temperatures.