High temperature low cycle fatigue deformation behaviour of forged IN 718 superalloy turbine disc

In the present investigation, low cycle fatigue deformation behaviour of forged turbine disc of IN 718 superalloy of different sections (rim, hub, and bore) was studied under asymmetrical waveforms (slow–fast and fast–slow) at 650 °C. The superalloy exhibited dynamic strain aging (DSA) by showing the manifestation of serrations during the lower strain rate plastic region of the hysteresis loop under asymmetrical waveforms. Irrespective of different sections, the superalloy showed marginally reduced fatigue life under slow–fast waveform as compared to fast–slow waveform. This was attributed to higher accumulation of LCF damage under slow–fast waveform as confirmed from slip band spacing than that of the fast–slow waveform.