Rapid fatigue testing to evaluate the competing effect of defects on the fatigue mechanism of powder bed fusion 316L specimens

Surface roughness and near-surface pores are inherent in metallic additively manufactured components and serve as fatigue crack initiation sites, reducing fatigue strength and service life. Although machining and polishing reduce surface roughness, they are costly, time-consuming, and limited to accessible areas. This study employs the stiffness method, a rapid fatigue test, to investigate the competing effects of surface roughness and lack-of-fusion defects on the fatigue performance of laser- and electron-beam powder bed fusion 316L stainless steel specimens. Optimising contour parameters achieves fatigue limits within 1.5% of polished specimens without post-processing. This rapid fatigue method is validated across nine surface conditions, producing fatigue limits within 2% of conventional testing results and reducing testing time by more than 1000 h. These findings show that surface optimization can significantly enhance fatigue performance and that rapid fatigue testing provides an efficient and reliable alternative for evaluating fatigue behavior in additive manufacturing parts.