Threshold conditions for thermocapillary formation of a deep cavity in the additive process for selective laser melting of a metal powder layer

Abstract

ABSTRACT The deep penetration mode at selective laser melting of a metal powder layer is determined by a special and intense hydrodynamic process in a thin molten layer at rapid heating of the metal by using a focused beam. This mode is also widely used in laser and electron beam welding. This indicates the similarity of hydrodynamic processes, which differ significantly in the parameters of the applied radiation (power, power density and focusing spot diameter). Threshold conditions of thermocapillary deep penetration (without evaporation) for various metals (Al, Cu, Fe and Ti) in a wide range of changes in beam parameters, including those used for selective laser melting of a powder layer, are investigated. The comparison of calculated and experimental values of the radiation parameters corresponding to the transition to the deep penetration mode for selective laser melting of the powder layer and laser welding is presented. The correlation of these values confirms the thermocapillary mechanism of the deep cavity formation and the similarity of hydrodynamic processes at welding metals by using a laser beam.