Comparison between modulated-pulsed and continuous wave laser powder bed fusion on an Inconel 625 alloy

Abstract Using pulsed or modulated laser irradiation for laser powder bed fusion (L-PBF) manufacturing can be an attractive solution for better controlling heat input, mastering geometry, and tuning microstructures of built samples. A comparison was made between a continuous wave (CW) and a modulated pulsed wave (PW) L-PBF process, considering high pulse frequencies (50 kHz), various duty cycles, and an Inconel 625 powder. In the first step, considering the precise shape of laser pulses, the peak powers were adjusted to provide similar mean powers between PW and CW and analyze the specific effect of the pulse regime at constant mean power. In the second step, single L-PBF beads were considered. The PW regime was shown to reduce the process window on ( P, V ) maps, increase powder-denudated widths around scan tracks, and slightly reduce the dimensions (depth, width and area) of fusion beads. In the third step, 3D samples were manufactured with PW (with duty cycles of 0.9 and 0.7) and CW regimes. The PW regime was shown to slightly increase the porosity rate, reduce the mean grain size by 30–40%, and modify the crystallographic texture.