According to [65,66], although both annealing and HIP decreased LCF strength of SLM steel 316L, they improved its HCF behaviour. LCF strength is more dependent upon tensile strength, and these heat treatments decrease the tensile strength due to the grain growth (according to Hall-Petch relationship). Thus, these heat treatments result in an inferior performance under LCF. However, this is not true for HCF since it is more sensitive to porosities and microstructural defects rather than tensile strength [39].