A bioinspired method for fatigue crack path tailoring and life enhancement in metals via additive manufacturing

• A Bio-inspired method is successfully employed to tailor crack path in metallic parts via additive manufacturing. • Weak features are used to enhance fatigue life of metallic components via additive manufacturing. • Crack path engineering is more feasible in materials with high fracture toughness. Inspired by natural systems, weak features can be strategically incorporated into materials to enhance mechanical response. This study presents, for the first time, a bioinspired approach enabled by additive manufacturing to tailor crack paths and enhance fatigue life in metallic components. Cylindrical holes of varying diameters and patterns were embedded as site-specific weak features in 18Ni(300) maraging steel produced via laser powder bed fusion. Fatigue crack growth tests in solution-annealed and aged conditions revealed that a region of weak features can effectively tailor crack path in solution-annealed condition while improving fatigue life in both conditions. In solution-annealed condition, crack deviation, bifurcation and transition of fatigue crack growth stage improved the fatigue life by 26%. In the aged condition, however, the lower fracture toughness limited the crack path tailoring, and retardation due to the crack re-initiation enhanced fatigue life by 14%. In both conditions, rough surfaces of holes restricted the maximum fatigue life improvement. This study demonstrates the unique potential of AM to integrate weak features into metallic materials for crack engineering. By refining the holes roughness in further steps, crack engineering via AM can be realized, offering a pathway to further optimize components’ durability.