Effect of scanning speed on fatigue behavior of 316L stainless steel fabricated by laser powder bed fusion

The effect of the scanning speed on the fatigue behavior of Laser Powder Bed Fusion (LPBF)-fabricated 316L steel is investigated in this paper. To this end, fatigue limits of specimen manufactured by different scanning speeds are determined by the self-heating approach. EBSD experiments and relative density measurements are carried out to characterize the microstructure and porosity. To analyze the influence of scanning speed on the microstructure (grain morphology, texture, dislocation density and stored energy) and fatigue property, a dislocation-density, crystal plasticity and stored energy-based fatigue model is developed. The inverse optimization method is combined with EBSD experiments and uniaxial tension experiments to identify the model parameters. The experimental results show a critical scanning speed, below which the fatigue limit stays almost unchanged and decreases drastically while the scanning speed is increased beyond. Furthermore, the simulation results show that the predicted fatigue limits correspond well to the experimental fatigue ones. From experimental and numerical results, it is deduced that the critical stored energy density and maximum temperature variation are functions of the porosity and can be used to differentiate the types of fatigue: microstructure-dominated or defect-dominated. This article provides new insights which can be further used in the optimization of fatigue behavior of LPBF 316L steel with respect to the scanning speed.