Low Cycle Fatigue Behaviour of Modified 9Cr–1Mo Steel at 600 °C

Abstract

Low cycle fatigue behaviour of modified 9Cr–1Mo steel was studied at different strain amplitudes from ±0.25 to ±0.50 %, at a strain rate of 10−2, at 600 °C. It exhibited cyclic softening at all the strain amplitudes. Masing and non-Masing behaviour was found to be strongly dependent on the strain amplitudes. Serrations of type A were observed at high strain amplitudes (≥±0.31 %) in the hysteresis loops, however the magnitude of serrations was low at low strain amplitudes. Examination of fracture surface revealed oxidation on the surface. Fatigue life at high strain amplitudes was affected by both dynamic strain ageing and oxidation. Cyclic softening may be attributed to formation of cell structure and annihilation of dislocations by recovery. © 2015, The Indian Institute of Metals - IIM.