Effect of laser energy density on microstructural properties of Inconel 625 alloy produced by selective laser melting

The main aim of this study is to investigate the microstructural properties of selective laser melted (SLM) Inconel 625 alloy as a function of laser energy density (LED) value. The layer thickness was selected as 30 µm for all samples. The samples were produced with 9 different LED values (0.78–2.80 J/mm3) using a 350 W laser power and scanning speeds ranging from 125 to 450 mm.s-1. Optical microscope images of the polished and etched samples in the XY, XZ, and XY planes were studied. The influence of the LED intensity on both the quantity and morphology of the pores in the structure was evaluated. A large number of pores with spherical shapes were observed in the samples with LED values of 1 J/mm3 and higher. The application of high energy density to the powders led to an increase in the solubility of gas, resulting in the formation of numerous spherical pores. This study indicated that the optimum LED value for IN625 alloy with a layer thickness of 30 µm is 0.78 J/mm3.