Multiscale analysis of interior cracking behavior of Ni-based superalloy fabricated by selective laser melting under very-high-cycle-fatigue at high-temperature

The fatigue test at high-temperature of selective laser melting Ni-based superalloy was performed to reveal the mechanism of interior cracking behavior by multiple analysis methods in the very-high-cycle-fatigue regime. Due to the inhibition effect of oxide layer, the interior multi-defects assisted facetted cracking becomes a significant failure mode. Large grain deformation mainly occurs on the fracture surface, and slip systems with high Schmid factor are activated by high-temperature. The precipitates in the matrix hinder the dislocation movement, resulting in dislocation accumulation and stress concentration increase, which makes it easier for microcracks initiation. The initiated microcracks with crack deflection caused by high angle grain boundaries propagate transgranularly to form a nearly circular region and undergo fast unstable growth, eventually leading to fracture.