ABSTRACT
In the SLS process, pulsed lasers are mostly used. Since only the surface of the powder particles is molten, consolidation can be achieved at much lower average power. Liquid bridges appear between the powder particles and are responsible for the bonding. The mechanical properties of the final part depend of the shape of these bonds. The goal of this study is to understand how the evolution of the liquid bridges (also called necks) is influenced by the laser parameters.
This work is divided into two parts. In the first one, we present a thermal model of the interaction between the laser beam and a single (metallic) grain. This model demonstrates the deep influence of the laser parameters onto the melting kinetics.
The second part of this work is an experimental study. We analyze electron micrographs of two particles after different type of laser treatment corresponding to different values of the power, repetition rate and pulse duration. These results have been obtained thanks to the development of an adequate system for the separation and the transport of the two particles.
The experimental results are used to clarify the exact relationships between the melting kinetics and the bounding mechanisms. They should be a key stone to develop a comprehensive model of the SLS process taking the thermal phenomena and the flow of molten material into account.
