Open AccessThreshold conditions for thermocapillary transition to deep penetration mode in selective laser melting of metal powder bed
Author(s) -
R. D. Seidgazov,
F. Kh. Mirzade
Publication year - 2020
Publication title -
iop conference series. materials science and engineering
Language(s) - English
Resource type - Journals
eISSN - 1757-899X
pISSN - 1757-8981
DOI - 10.1088/1757-899x/759/1/012023
Subject(s) - keyhole , materials science , selective laser melting , laser , weld pool , welding , laser beam welding , laser power scaling , composite material , optics , gas tungsten arc welding , microstructure , physics , arc welding
The keyhole mode of selective laser melting (SLM) of metal powder bed in additive technology is characterized by an intensive hydrodynamic process in a thin molten layer. Such a mode is widely used also in laser and electron beam welding indicating the similarity of hydrodynamic processes in these technologies despite a significant difference of operating parameters. The threshold conditions of thermocapillary keyhole mode transition for various metals (Cu, Fe, Ti) in a wide range of beam parameters used for selective laser melting of metal powder layer and laser welding are investigated. The condition of threshold for thermocapillary transition into keyhole mode by sticking of viscous layer to the solid boundary is formulated. The fulfillment of this condition is confirmed by the convergence of estimated values of the viscous layer thickness and the molten layer depth during the transition to a keyhole mode. Analytical estimates of keyhole threshold and comparisons with experimental values of beam power and spot size corresponding to the transition in keyhole mode for SLM processes and laser welding are presented. The correlation of these values confirms the thermocapillary mechanism of cavity formation and the similarity of hydrodynamic processes in laser welding and SLM processing in keyhole mode at wide range of operating parameters.