Contact angle evolution during selective laser melting

The researches about the connection of the geometrical feature and the melting and solidification behavior of the molten pool during selective laser melting (SLM) are necessary with the development of additive manufacturing (AM) technique. This research has paid attention to the contact angle evolution during SLM. A model has been built for analysis. The extreme state and the equilibrium state of the contact interface have been solved for the molten pool spreading. As the molten pool is solidified during non-equilibrium state, we propose the combined action of the fluid flowdriving forces and the lifetime of themolten pool as themain reasons for the contact angle evolution. Based on the thermal simulation performed, it is confirmed that the shear stress induced by the surface tension gradient, the evaporation recoil pressure and the lifetime of the molten pool all increase first and then become stable as tracks increase. As a consequence, the contact angle decreases first and then becomes stable. (C) 2017 Elsevier Ltd. All rights reserved.