Creep-Fatigue Interaction Life Prediction and Fracture Behavior of 1.25Cr0.5Mo Steel at 560 °C

In this article, a series of stress-controlled creep-fatigue interaction (CFI) tests on 1.25Cr0.5Mo steel at 560 degrees C are conducted. The cyclic deformation behavior of 1.25Cr0.5Mo steel with different stress levels is analyzed from the perspective of hysteresis loops, and then, the hysteresis cyclic characteristics and average strain parameter variation law under high-temperature CFI are also analyzed. In terms of calculation, the average strain rate of half-life is considered the main factor affecting fracture life. A life prediction equation based on ductile fatigue theory and effective stress concept is established, introducing the average strain rate of half-life as the parameter. The existing experimental datasets of 1.25Cr0.5Mo steel are used to validate the predictive ability of the model under different load conditions. The results show that all the experimental data points fall into a range within a scatter band of +/- 2 on life prediction. Based on the combination of scanning electron microscopy and transmission electron microscopy characterization, the fracture behavior and damage mechanism are explored. The reasons are revealed for accelerated softening and premature failure during CFI loading.