Low cycle fatigue behavior of MAR-M247 nickel-based superalloy from 500 to 900 ° C: Analysis of cyclic response, microstructure evolution and failure mechanism

Low cycle fatigue behaviors of MAR-M 247 superalloy were investigated at 500 degrees C, 700 degrees C and 900 degrees C. The detailed deformation mechanisms were characterized by scanning electron microscopy (SEM), electron back- scatter diffraction (EBSD) and transmission electron microscopy (TEM) and the critical resolved stress to active different deformation mechanisms were calculated. The results show that crack propagates along favorable {111} plane at 500 degrees C, and anti-phase boundary (APB) shearing is the main deformation mechanism. At intermediate temperatures, the cracking mode is similar to 500 degrees C. The dislocation pinning at L-C lock leads to premature failure. It is difficult for {111} (110 ) slip system to shear hard oriented grain with low Schmid factor at 900 degrees C. Dislocation movement is achieved by Orowan by pass process and thermal activated dislocation climb at high temperature. In addition, the improved life prediction model based on energy method has been constituted and discussed at different temperatures.