Enhancing fatigue resistance of additively manufactured novel Ni-based superalloy via crystal orientation and intergranular strain compatibility: An experimental and numerical investigation

To assess the viability of additively manufactured (AM) alloys in reusable liquid rocket engines, a novel Ni-based superalloy with a complex microstructure was prepared via selective laser melting. The effect of the AM sample microstructure on fatigue crack initiation and propagation was quantitatively elucidated via experimental characterization and crystal plasticity (CP) simulation. The findings indicate that the AM sample exhibited enhanced low cycle fatigue performance compared to traditional wrought (W R ) samples. Specifically, in the initiation stage, the < 001 > texture orientation along the build direction promoted intergranular strain compatibility in AM samples. Meanwhile, the high geometric compatibility factor between adjacent grains disperses local slip accumulation. This synergistic effect promotes a more uniform distribution of plastic deformation, resulting in a longer initiation life than W R samples. In contrast, W R samples exhibit early crack initiation due to strong strain localization caused by the large elastic modulus gradient at twin boundaries. During the propagation stage, the similar grain orientations of the AM samples resulted in a small difference in the transgranular crack deflection angle, which accelerated the propagation of fatigue cracks. The large orientation difference between adjacent grains in the W R sample caused a significant deflection of the crack propagation path, which in turn reduced the crack propagation rate. Overall, although the W R sample exhibited stronger resistance to crack propagation, its early severe strain localization accelerated damage accumulation and limited overall fatigue performance. Finally, the Coffin-Manson equation based on accumulated plastic slip correction achieves accurate prediction of cross-scale life in both AM and W R samples.