Fatigue life curves of alloy 617 in the temperature range of 800–950 °C

The cyclical behavior of Alloy 617 was examined at 25 °C and high temperatures of 800, 850, 900, and 950 °C in air to obtain its fatigue life curves. The specimens tested at 25, 800, and 850 °C cyclically hardened, whereas those tested above 900 °C cyclically softened from the first cycle, that is, their fatigue life was reduced at high temperatures owing to loss of strength. Parameters of the typical Coffin−Manson−Basquin relationship were determined for each test temperature. Interestingly, no significant difference in fatigue life was observed for the specimens tested in the range of 800–950 °C. Owing to the similarity in fatigue life, we determined fatigue strength and fatigue ductility exponents that could be applied for this temperature range. The parameters obtained were close to the universal slopes, although the fatigue ductility exponent was slightly different. The proposed fatigue life curves were compared with those presented in ASME code.