Laser-induced plume investigated by finite element modelling and scaling of particle entrainment in laser powder bed fusion

International audienceAlthough metal vaporisation has been observed in several laser processes such as drillingor welding, vapour plume expansion and its induced side effects are not fully understood.Especially, this phenomenon is garnering scientific and industrial interest since recentinvestigations in laser powder bed fusion (LPBF) have designated metal vaporisation as mainsource of denudation and powder spattering. The present study aims to provide a new insighton the dynamics of laser-induced vaporisation and to assess the potential of different gasesfor particle entrainment. A self-consistent finite element model of laser-induced keyhole andplume is thus presented for this purpose, built from a comprehensive literature review. Themodel is validated with dedicated experimental diagnostics, involving high-speed imagingto measure the ascent velocity of the vapour plume. The transient dynamics of vapour plumeis thus quantified for different laser incident intensities and gas flow patterns such as themushroom-like structure of the vapour plume are analysed. Finally, the model is used as a toolto quantify the entrainment flow expected in LPBF and an analytical model is derived to definea velocity threshold for particle entrainment, expressed in term of background gas properties.Doing so it is possible to predict how denudation evolves when the gaseous atmosphere ischanged