Influence of the position and size of various deterministic defects on the high cycle fatigue resistance of a 316L steel manufactured by laser powder bed fusion

Abstract

Optimized 316L steel samples were manufactured using laser powder bed fusion and tested in high cycle fatigue at R = 0.1. They showed microstructural crack initiation and outstanding fatigue properties. Additional fatigue testings were then carried out on samples containing deterministic defects of various sizes and positions. All results summarized in a Kitagawa-Takahashi diagram show that the critical defect size is around 20 µm for surface defects and reach 380 µm for internal pores. Fracture surface analysis revealed that the large size gap between surface and internal fatigue crack initiation could be linked to the local gaseous environment in the pores.