Influence of laser power on mechanical properties and pitting corrosion behavior of additively manufactured 316L stainless steel by laser powder bed fusion (L-PBF)

Abstract

316L stainless steel parts were additively manufactured via laser powder bed fusion under different laser powers. We investigated the influence of laser power on the microstructure and mechanical properties of the printed parts by conducting scanning electron microscopy, X-ray diffraction, microhardness and tensile tests. In addition, we performed electrochemical corrosion tests including cyclic potentiodynamic polarization and electrochemical impedance spectroscopy in 3.5 wt% NaCl solution to study the influence of laser power on the corrosion behavior of as-printed parts. The results indicate that as-printed parts exhibit a preferential orientation of (220) direction, and increasing the laser power results in grain refinement of the samples, but excessive laser power can lead to a re-increase in the grain size of the samples. Excessively low laser power can result in the formation of lack of fusion pores, while excessively high power can lead to the formation of keyhole pores. These defects lead to a reduction in tensile performance. Significant differences in corrosion resistance are observed for the parts printed with different laser powers, and between the building direction and normal direction. Some defects, such as micropore, MnS inclusions and boundaries of melt pools, have an impact on the pitting corrosion resistance of printed parts. However, due to low content of MnS inclusions, the presence of pore defects remains the major factor in the pitting corrosion process. Laser powers in the range of 300–375 W can effectively reduce pore defects and improve the resistance of pitting corrosion. These findings emphasize the importance of optimizing the laser power to enhance the overall performance and pitting corrosion resistance of 316L stainless steel parts.