High-temperature high cycle fatigue performance of laser powder bed fusion fabricated Hastelloy X: Study into the microstructure and oxidation effects.

[Display omitted] • Effect of grain oxidation on high-temperature high-cycle-fatigue performance of laser powder bed fusion Hastelloy X was analyzed. • The high-temperature high-cycle-fatigue performance of LPBF HX, in this study, is superior to that of Cast HX. • The presence of annealing twins increases the resistance to the initiation and propagation of fatigue cracks. • Dynamic recrystallized grains formed during the fatigue loading process, further increasing the crack propagation resistance. High-temperature fatigue properties are critical for laser powder bed fusion (LPBF) fabricated Nickel-based superalloy Hastelloy-X (HX) used in aero engines. In this study, superior high-temperature high-cycle fatigue properties of LPBF HX were achieved. The detailed investigations show that the grain boundary oxidation promoted by the different deformation modes between neighboring grains, despite the reduced oxygen-related damage in the coarser LPBF HX microstructures, are the potential causes for the inter-granular fatigue crack initiation and the subsequent crack coalescence. In the meantime, the crack propagation could be hindered by the refined carbides and annealing twins with Σ3 misorientation (60°/〈1 1 1〉) in LPBF HX. Furthermore, the recrystallized grains formed ahead of the crack tip due to the severe deformation within the plastic zone and high testing temperature have different crystallographic orientations, which leads to the crack propagation path changes and increases the fatigue crack propagation resistance. [ABSTRACT FROM AUTHOR]