A physically-based fatigue model and experimental testing for PBF-LB 316L

This work examines the effect of build orientation and post-build machining on tensile and fatigue behaviour of stainless steel (SS) 316L specimens produced by laser beam powder bed fusion (PBF-LB). X-ray diffraction and tensile and fatigue testing are used to investigate residual stresses and fatigue. The results demonstrated: (i) horizontal builds are stronger but less ductile than vertical builds, and (ii) effect of machining on tensile and fatigue behaviour, namely, increasing yield, tensile and fatigue strength but decreasing ductility. Effect of orientation was more pronounced for as-built specimens. Significant benefit of machining for fatigue was attributed to reduced surface roughness and compressive residual stresses. This work adapts and verifies the physically-based Tanaka-Mura (T-M) fatigue crack initiation model for PBF-LB SS316L. The model captures the beneficial effects of machining via measured surface roughness and residual stresses for both horizontally- and vertically-built specimens.