3.1. Effects of building orientation Building orientation has a substantial influence on the static and dynamic mechanical properties of SLM steels. In other words, the direction of applied load with respect to the direction of built layers is a determining factor for the fatigue strength under either high-cycle fatigue (HCF) or low-cycle fatigue (LCF) regimes [28,35,37,38]. In this paper, specimens with the building direction parallel to their loading axis are considered as vertical, while the ones with the building direction normal to the loading axis are referred as horizontal specimens, as shown in Fig. 2.