Effect of high temperature on failure behavior of additively manufactured superalloy under fatigue

The axial loading fatigue tests with stress ratios of -1 and 0.1 at 650 °C were performed to examine the fatigue failure mechanism of a Ni-based superalloy manufactured by selective laser melting (SLM) in the long life regime at high temperature. As a result, the interior cracking with a typical circular rough area (CDA) is a predominant failure mode. Especially in the very high cycle fatigue regime, the CDA is mainly consisted of the facets with distinct grain misorientation. Combined with the analysis of electron backscatter diffraction, the formation of facet is greatly related to the slipping within the grains located in the highest shear stress plane, especially under the assistance of microstructural defects. The interior cracking mechanism of SLM Ni-based superalloy in the long life regime at elevated temperature is elucidated.