This study aims at characterizing the role of strong anisotropy in fatigue crack growth for a superalloy processed by additive manufacturing. The choice has been made to design significant differences into microstructure by playing on the processing parameters of IN718 obtained by laser powder bed fusion, and submitted to direct aging. As a consequence of the chosen process parameters, textures promoting elongated grains in the building direction, <001> and <110> grains orientations and subsequent high level of elastic and viscoplastic anisotropy were observed. 

The fatigue crack growth of these materials have been tested at high temperature. Again, the anisotropy plays a key role in the crack path, which is carefully analyzed by EBSD analysis of the crack vicinity. To access fatigue crack driving forces in the context of complex 3D crack shape, finite element analysis was proceeded taking care of crack shape description and J integral derived from G-theta method, convenient for anisotropic material.

Finally, fatigue crack growth was observed to be strongly dependent in path and in rate on the chosen processing parameters and considered orientation for specimens. The cracks grow preferentially in the vicinity of grain boundaries with potential weak interdendritic areas for all orientations of specimen, except the one for which loading is in the processing direction. In this case, cracking is mostly transgranular and yields to a strong impact of processing parameters.