Low Cycle Fatigue And Life Prediction Of Alloy 800h Weldment At 750 Degrees C

This work aims to investigate the low-cycle fatigue and life prediction of alloy 800H weldment at 750 degrees C. Low cycle fatigue tests were conducted using a series of fully reversed strain-control tests at four different strain amplitude, namely +/- 0.3, +/- 0.45, +/- 0.6 and +/- 0.75 %, under a constant strain rate of 10(-3)/s. In all test conditions, the fatigue life of alloy 800H weldments decreased with increasing the strain amplitude. The cyclic stress response behavior of the base metal showed the initial cyclic hardening phenomenon, whereas the weldments showed the cyclic softening phenomenon. The life evaluation of the base metal and weldment was evaluated by the Coffin-Manson method. For both the base metal and weldment, the low cycle fatigue lives predicted using the Coffin-Manson method were found to coincide well with the experimental data. The transition life of the weldment was lower than that of the base metal. Finally, under all testing conditions, crack initiation and propagation data showed the failure mode to be typically transgranular.