Particle scale modelling of powder recoating and melt pool dynamics in laser powder bed fusion additive manufacturing: A review

Particle scale modelling of the process physics involved in laser powder bed fusion (LPBF) is a recent research hotspot, and many efforts have been made in the literature. However, a comprehensive review of the physics in LPBF and the effects of key variables such as powder- and operation-related parameters, and the mechanisms of defects formation is still lacking. This paper aims to offer a state-of-the-art review on multi-physics related to metal powder recoating and further melting and solidification process. The studies on powder bed recoating explored by discrete element method are presented first, including model theory and validation, effects of process parameters, and physics of particle flow and size segregation. Then powder melting approach based on computational fluid dynamics and the involved phenomena such as melt pool dynamics, keyhole dynamics, defects formation mechanisms of pores, and balling and spattering are described. The needs for future research are also discussed. • Powder bed recoating explored by discrete element method (DEM) is reviewed. • Physics of powder flow and size segregation in powder spreading is presented. • Powder melting based on computational fluid dynamics (CFD) is summarized. • Melt pool flow dynamics and defects formation are discussed.