Numerical modeling of melt-pool behavior in selective laser melting with random powder distribution and experimental validation

A three dimensional selective laser melting process simulation is developed to investigate the melt-pool behavior of a randomly-distributed powder bed with keyhole formation by Nd-YAG laser. In order to simulate a randomly-packed powder bed, the discrete element method is introduced to ensure a close match with real conditions. Also, to show the importance of evaporation during laser melting, the melt pool temperature, melt pool dimensions and the surface morphology are used as metrics for comparison. Numerical results show that the keyhole was formed as evaporation occurred, and the shape of the melt pool was narrow and deep, which implied the main direction of heat transfer had changed to being vertical. Through simulation, the transition from keyhole formation to the final convex surface at a local area was discovered. The simulation results are validated via good agreement with the experiment.