Computational modeling of the effects of process parameters on the grain morphology of additively manufactured stainless steel

Identifying the suitable process parameters is one of the necessities to control the microstructure, and consequently various properties of additively manufactured (AM) parts. To obtain suitable process parameters, it is crucial to understand the effects of each process parameter on various aspects of microstructure of the printed material. In this work, we have conducted a parametric study on the effects of AM process parameters on the grain morphology of the metallic parts, fabricated via directed energy deposition (DED), through the Kinetic Monte Carlo (KMC) simulations. The characteristics of the melt pool and the heat-affected zone (HAZ) were incorporated into the models, and microstructural effects of altering the layer thickness, hatch spacing, scanning speed, and laser power were investigated. We used the Rosenthal equation, to predict the geometry of the melt pool and heat-affected zone formed by certain laser powers. The resulting grain morphology (i.e. the grain size and inclination) was analyzed for a large number of combinations of different process parameters. It was observed that by increasing the laser power, the number of fine and equiaxed grains decreases. On the other hand, increasing the scanning speed had a significant effect on formation of more fine grains in the final model.