Effects of laser-beam diameter on melt pool characteristics and grain formation in Fe-3.4 wt%Si alloy made by powder bed fusion

Abstract

This study explores the interaction between laser-induced thermal processes and fluid dynamics that govern the formation and morphology of the melt pool during Laser Powder Bed Fusion of Fe-3.4 wt%Si powder. We examined the configuration and dynamics of the melt pool that develops on the powder substrate as formed by laser beams of various diameters B. To understand the process of melt pool formation, we combine express normalized thermodynamic variables in terms of the dimensionless Pe<acute accent>clet number. This analysis helps understand the geometric variations in the melt pool during irradiation with lasers of uniform power and scanning speed. If the interaction time is sufficient to induce melting, the melt pool depth increases significantly as B increases from 100 mu m to 200 mu m, despite a reduction in surface energy density due to the increase in B. Additionally, even if the depth-to-width ratio of the melt pool indicates that it is in keyhole mode, the thermodynamics may not permit formation of this mode. The inclusion of surface-activating elements can affect the Marangoni flow direction of the molten pool and alter its characteristics. We also demonstrate correlations between the melt pool&apos;s microstructural and textural characteristics and its geometric features.