Impact of annealing treatment on the fatigue behavior of Inconel 625 produced by laser‐based powder bed fusion

Abstract : Laser-based powder bed fusion (LPBF) is attractive to build complex parts in spite of the low machinability of Inconel 625. The LPBF microstructures and tensile properties are well documented in literature. But fatigue properties and impact of the LPBF intrinsic defects and microstructures on the crack initiation and propagation mechanisms are uncommon. Low and high-cycle fatigue tests at room and service temperature presented in this paper prove that the LPBF defects shorten the crack initiation stage. After annealing heat treatment, the microstructure adapts to the defects, and the fatigue response becomes similar to a free defect material. The fatigue life of as-built Inconel 625 is lower than 50% of its monotonic yield tensile strength (YTS) while the annealed material reaches 100% of its YTS. The propagation rate is slowed by the homogeneous annealed microstructure and improved ductility resulting from removal of dislocation cells and changes in grain morphology.