Evaluation of near immersion active cooling on the microstructure and mechanical properties of AISI 316L stainless steel obtained with additive manufacturing by DED-Arc

The directed energy deposition arc (DED-Arc) has been extensively used to develop metallic parts with varying complexities. A major challenge for austenitic stainless steels is managing heat accumulation due to their low thermal conductivity. This study aimed to characterize the microstructure and mechanical properties of AISI 316L preforms manufactured by additive manufacturing (AM) under different deposition paths and cooling conditions. Samples underwent macro- and microstructural analyses, and tensile and hardness tests to evaluate their mechanical behavior. Additionally, the effect of active cooling using near immersion active cooling (NIAC) in water on the microstructure was assessed by examining the secondary interdendritic spacing and ferritic phase fraction. The NIAC technique has shown potential for enhancing productivity by producing preforms with more uniform thickness and consistent solidification/cooling conditions throughout the multiple layers. This approach eliminated deposition idle time, leading to a productivity increase of up to 108%. Microstructures obtained with active cooling were more refined than those resulting from natural cooling, evidenced by a reduction in secondary interdendritic spacing and an increased fraction of delta ferrite. These microstructural changes resulted in higher hardness and mechanical strength in the material processed with the NIAC technique. However, difficulties in precisely controlling the water level resulted in increased apparent porosity when using the NIAC technique.