Modeling analysis of the effect of laser transverse speed on grain morphology during directed energy deposition process

Directed energy deposition (DED) is an advanced additive manufacturing process which can deposit or fabricate a part with complex and nontraditional geometries in many kinds of engineering structural materials, high-temperature materials, and anti-corrosion materials. The fed metallic powder is melted by a laser beam with highly concentrated energy on the substrate surface. In this manufacturing process, different laser transverse speeds can significantly affect the microstructural morphology of the deposited layer. Some microstructural morphologies observed in DED may appear in classic solidification processes. However, the effect of mobile heat sources which vary with time and location can result in significant microstructural heterogeneity. In order to investigate the laser transverse speeds' effects on the microstructural morphology in DED processes, a Kinetic Monte Carlo (KMC) Potts model was utilized to exactly predict the grain evolvement under different laser transverse speeds in this study. Three increasing transverse speeds, 450mm/min, 600mm/min, and 1000mm/min, were chosen and then investigated. The predicted microstructural morphology in depositions with these three different laser transverse speeds was quantified and analyzed. The processing parameters in the KMC Potts model were cited from a previous reference and have been validated with experimental EBSD microstructural images.