Energy density should be optimized to have a high-quality final product with an acceptable fatigue performance. There are several ways to change the energy density of the SLM process, and it is generally changed by modifying the laser power and/or its deposited layer thickness [48,65,75]. For example, according to [75], utilizing either too high or too low energy densities decreased HCF life and ΔKth for SLM steel 316L. Furthermore, the effects of energy density on the fatigue strength was more prominent in the HCF regime.