Selective laser melted 316L stainless steel: Influence of surface and inner defects on fatigue behavior

• Published in: International journal of fatigue Vol. 172; p. 107664
• Main Authors: Rivolta, Barbara, Gerosa, Riccardo, Panzeri, Davide
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-07-2023
• Subjects: Defects; Fatigue limit; Fractography; S-N curves; Stainless steel; S-N curves; Fatigue limit; Fractography; Stainless steel; Defects
• ISSN: 0142-1123; 1879-3452
• DOI: 10.1016/j.ijfatigue.2023.107664

•Defects size and content affect fatigue strength of SLMed 316L stainless steel.•Fatigue limits are determined in both the as-built and grinded conditions.•Crack nucleation occurs close to the surface from lack-of-fusion pores.•Fracture mechanics allows to study fatigue failures from threshold perspective.•Fatigue limits are predicted from the micro-notch length at 50 % probability.
In additive manufacturing, despite its several indisputable advantages, detrimental variables to fatigue strength still remain poor surface finishing and porosities. However, because the majority of defects locate close to the surface, their mechanical removal is expected to appreciably improve fatigue strength. Considering SLMed 316L, fully-reversed rotating-bending fatigue tests in both as-built and machined conditions are performed. Fatigue failures are discussed using the Kitagawa-Takahashi diagram. In each condition, the fatigue stress is related to the equivalent micro-notch length of the killer defect. Then, this work analyses the possibility of predicting fatigue limits at 50 % probability considering the equivalent micro-notch length.