Influence of interlayer dwell time on microstructure and mechanical properties additively manufactured 316L stainless steel by laser directed energy deposition

Laser directed energy deposition (LDED) is widely utilized due to its high precision, fast processing speed, small heat affected zone, strong machinability, environmental protection, energy saving, and high reliability. 316L stainless steel is one of the most extensively studied materials employed in the LDED process. The process parameters of LDED are known to affect the thermal history process, which subsequently influences the microstructure and mechanical properties of the final product. Therefore, the effects of different interlayer residence times (interlayer cooling after each deposition of four layers to enhance production efficiency) on the microstructure and mechanical properties of LDED 316L stainless steel are discussed in this paper. The experimental results indicate that with the extension of the interlayer residence time (IDT), the morphology of the molten pool becomes increasingly stable, the surface quality of the component improves, and the grains are refined. When the IDT is set to 360 s, it is observed that the ultimate tensile strength of the sample is 34% higher compared to when the IDT is 0 s, the elongation is increased by 47%, and the hardness is enhanced by 13%. These findings underscore the importance of optimizing the laser interlayer residence time to improve the overall performance of 316L stainless steel parts.