Low Cycle Fatigue Behavior of a Directionally Solidified Nickel-Based Superalloy: Mechanistic and Microstructural Aspect

Abstract

In the present research, efforts were made to understand the mechanistic and microstructural aspects of the low cycle fatigue failure of a directionally solidified (DS) nickel-based superalloy under relevant operating conditions. The differences between the dislocation structures observed during different temperatures and strain amplitudes are clearly shown in the transmission electron (TEM) micrographs and are giving rise to the divergence in associated LCF responses. The deformation mechanism changes as a function of temperature. While shearing of gamma '-precipitates by stacking faults is the dominant deformation mechanism at the lowest temperature (750 degrees C), gamma '-coarsening and dislocation networks are prevalent at the highest temperatures (930 degrees C). Mixed deformation behavior is observed at the intermediate temperature (850 degrees C). Constituent's phases of the alloy also play crucial roles during deformation.