Thermomechanical Fatigue and Creep–Fatigue Interaction of Inconel 718 Additively Manufactured by Laser Beam Powder Bed Fusion

This study investigates the Ni‐based superalloy Inconel 718 produced by laser beam powder bed fusion (PBF‐LB) under thermomechanical fatigue (TMF) loading. Strain‐controlled TMF tests under in‐phase and out‐of‐phase conditions were conducted in the temperature range from 300°C to 650°C. To increase creep–fatigue interaction, tensile dwell times of 10 min at 650°C were introduced in some in‐phase TMF tests. After hot isostatic pressing, solution annealing and age‐hardening, the PBF‐LB material recrystallized and exhibited finely dispersed γ ″ precipitates, typical of Inconel 718. In this state, the material showed a cyclic deformation behavior comparable to that of conventionally‐rolled Inconel 718. In tests without dwell times, the TMF lifetimes of PBF‐LB Inconel 718 reached almost those of conventionally‐rolled Inconel 718. Introducing dwell times significantly reduced the TMF life of PBF‐LB Inconel 718. The results suggest that this effect can be attributed to a lack of grain boundary precipitates, which may facilitate grain boundary sliding and promote intergranular crack propagation.