Fatigue Behavior of Additive Manufactured 304L Stainless Steel Including Surface Roughness Effects

The fatigue behavior of additive manufactured parts in the as-built surface condition is typically dominated by the surface roughness. However, the fatigue behavior of 304L stainless steel fabricated by laser beam powder bed fusion shows less sensitivity to surface roughness under strain-controlled loading conditions than other additive manufactured materials. Under force-controlled conditions, however, the high cycle fatigue resistance is much lower for the as-built surface condition than the machined one. This study investigates the underlying mechanisms responsible for fatigue failure for each condition (i.e. strain-controlled or force-controlled). The corresponding cyclic deformation behavior was characterized, and a thorough fractography analysis was performed to identify the features responsible for crack initiation. Results indicate that the crack initiation features in both loading conditions are similar, and that the reduced high cycle fatigue resistance for force-controlled fatigue loading compared to strain-controlled one is related to differences in the cyclic deformation behavior of the material.