Tailoring microstructure and strength through selective remelting in laser powder bed fusion

Additive manufacturing provides new opportunities to manipulate local microstructure to enable strengthening pathways for austenitic stainless steels. Laser beam powder bed fusion techniques, however, are limited by their narrow process window, as compared to other additive manufacturing techniques. In this work, the use of layer-wise remelting is explored to expand the available process window in laser powder bed fusion to manipulate the microstructure and increase strength while minimizing porosity. Several single melt process conditions are considered for 316L stainless steel along with additional low energy and high energy remelts to evaluate the effect on grain morphology, texture, porosity, and hardness. Results demonstrate remelting as an effective approach to tune grain size and texture to achieve high hardness while reducing the overall porosity. While the data suggest that the optimal single melt process set results in the lowest porosity, remelting provides a pathway to reduce porosity for non-optimal process parameters, minimize grain growth, and increase strength.