Elucidating the relations between monotonic and fatigue properties of laser powder bed fusion stainless steel 316L

Abstract

The laser powder bed fusion (L-PBF) technique builds parts with higher static strength than the conventional manufacturing processes through the formation of ultrafine grains. However, its fatigue endurance strength σf does not match the increased monotonic tensile strength σb. This work examines the monotonic and fatigue properties of as-built and heat-treated L-PBF stainless steel 316L. It was found that the general linear relation σf = mσb for describing conventional ferrous materials is not applicable to L-PBF parts because of the influence of porosity. Instead, the ductility parameter correlated linearly with fatigue strength and was proposed as the new fatigue assessment criterion for porous L-PBF parts. Annealed parts conformed to the strength-ductility trade-off. Fatigue resistance was reduced at short lives, but the effect was partially offset by the higher ductility such that comparing with an as-built part of equivalent monotonic strength, the heat-treated parts were more fatigue resistant.