Investigation of the High‐Cycle Notch Fatigue Behavior of L‐PBF Inconel 718 Under Two Stress Ratios

Notch and stress ratio play crucial roles on the fatigue behavior of L‐PBF Inconel 718. In this study, high‐cycle fatigue tests were conducted on smooth and notched specimens of L‐PBF Inconel 718 under two stress ratios ( R = −1 and 0.5). The multiple‐site crack initiation was only detected in notched specimens, and its probability at R = −1 is higher than that at R = 0.5. Secondary cracks were found in the crack propagation region of failed specimens at R = 0.5 but not at R = −1. The secondary cracks tended to propagate in the grains with high Schmid factors, and their maximum length in notched specimens is considerably shorter than that in smooth specimens. A novel method combining the theory of critical distance and a modified Walker model can well predict the notch fatigue life of L‐PBF Inconel 718 under both stress ratios.