Numerical investigation of the melt pool geometry evolution during selective laser melting of 316L SS

Abstract

In this study, the melt pool size, precisely its width and depth, are numerically investigated for a wide range of values for both laser power and beam speed. A thermal model, developed on Ansys Additive Science, simulates the SLM of a single bead. A parametric study is achieved aiming at understanding the melt pool evolution and the defects appearing while varying these two parameters. The discussed porosity defects, namely the LOF and keyhole, are determined using the calculated melt pool dimensions and through mathematical correlations from the literature. Moreover, these numerical results are validated with experimental results for the reliability of the study. This investigation reveals a proportional relationship between the melt pool size and the laser power and an inversely proportional relationship with the scan speed. The optimal combination of these two parameters has to be well studied to avoid LOF and keyhole, which is afforded by this paper. At lower laser power levels, such as 100 W, it is advisable to choose a slower scan speed ranging from 400 to 500 mm/s. As the laser power increases, so does the optimal scan speed. For instance, with 150 W, the ideal speed falls between 600 to 900 mm/s. Similarly, for 200 W, the recommended scan speed range extends from 900 to 1200 mm/s, and for 250 W, the optimal speed range lies between 1100 and 1400 mm/s.