Low-cyclic fatigue behavior of modified 9Cr-1Mo steel at elevated temperature

The low-cycle fatigue behavior of indigenously developed modified 9Cr-1Mo steel has been evaluated using a constant strain rate (1×10−3 s−1) at ambient temperature (25 °C) and at elevated temperatures (500-600 °C) over the strain amplitudes varying between ±0.7% and ±1.2%. Cyclic stress response showed a gradual softening regime that ended in a stress plateau until complete failure of the specimens. The estimated fatigue life decreased with the increase in test temperature. The effect of temperature on fatigue life was more pronounced at lower strain amplitudes. The cyclic deformation behavior at different temperatures has been analyzed from hysteresis loop and also in view of the changes taking place in dislocation structure and dislocation-precipitation interaction. Evaluation of low-cycle fatigue properties of modified 9Cr-1Mo steel over a range of test temperature can help in designing components for in-core applications in fast breeder reactors and in super heaters for nuclear power plants.