Low Cycle Fatigue of CMSX‐4 in Off‐Axis Orientations and the Effect of a Multi‐Axial Stress State

Abstract

The current research advances our understanding of the isothermal low-cycle fatigue (LCF) behavior of the nickel based superalloy CMSX-4 in off-axis orientations. This has been achieved through the assessment of a plain specimen geometry extracted from HIP'ed (hot isostatically pressed) and fully heat treated single crystal stock materials in seven specific orientations, deliberately selected to sample various polar and off-axis conditions across the stereographic triangle. Uni-axial strain controlled loading configurations were employed at 750°C and 950°C. It is recognized that fatigue life assessments of various on-axis pole orientations have been reported previously [1-5], however, information describing additional off-axis orientations is notably sparse in the open literature.Complimentary work carried out on a novel specimen design tested under combined tension-torsion, strain controlled loading is also presented. Detailed finite element stress analysis was initially conducted to optimize the hollow specimen design, wherein parallel, opposed, flat faces were introduced onto the external gauge section, deliberately aligned normal to a secondary orientation, i.e.<001><010>.