Pore defects and corrosion behavior of AISI 316L stainless steel fabricated by laser directed energy deposition under closed-loop control

Abstract

During laser directed energy deposition (DED) process, the state of the melt pool is closely related to the forming quality and overall properties of the component. As an important factor feeding back into the melt pool morphology, the stability of the melt pool width is influenced by thermal effects. When depositing thin-walled parts, the single-layer stacked deposition pattern makes this effect more intuitive. In this work, thin-walled parts of AISI 316L stainless steel with 40 layers were fabricated by DED in both traditional and control modes. A coaxial infrared camera was used to acquire melt pool images and extracted the melt pool width. Proportional-integral-derivative (PID) control was also introduced to ensure the stability of the melt pool width by adjusting the laser power in real time. In addition, the effects of melt pool width on the surface roughness, porosity and corrosion performance of thin-walled parts were studied. The results showed that the stable melt pool width reduced the surface roughness of the thin-walled parts by a maximum of 57.5 % and the porosity by 52.5 % compared with the traditional mode. The good forming quality significantly improved the corrosion resistance, and the pitting potential (Epit) increased by ~18.6 %.