Shrink line impact on the fatigue resistance of Inconel 718 parts manufactured by powder bed fusion of metals using a laser beam

The powder bed fusion of metals using a laser beam enables the additive manufacturing of thin-walled and topology-optimized geometries. These geometries feature structural transitions, where shrink lines form notches on the outer surface of the part and reduce the dimensional accuracy. The influence of shrink-line-shaped notches on the fatigue life has not been determined yet. This paper presents the impact of a shrink line on the fatigue resistance. A standardized specimen was prepared with a representative shrink line notch whose dimensions were varied. The resulting notch shape was optically measured and experimentally investigated concerning the fatigue properties and the fracture behavior. A position-dependent formation of the resulting shrink line notch during the manufacturing was identified. The shrink line dimensions demonstrated a significant influence on the fatigue resistance and the fracture mechanism. The results indicate that existing calculation methods can be applied for shrink line notches in the future.