Heat Transport Phenomena Governing Selective Laser Melting: Numerical Investigation and Experimental Validation

Selective laser melting (SLM) is an additive manufacturing technology, applicable to a wide range of materials and products demanding a high degree of customization. Besides having potential advantages over conventional manufacturing routes, layer-by-layer synthesis poses challenges concerning the understanding of physical phenomena governing the selective laser melting process. In this study heat transport phenomena during selective laser melting are investigated numerically. A numerical model based on laser energy absorption and its transport in granular media is presented, which is especially relevant to laser melting of metal powders. The model predicts laser radiation propagation in the powder bed and subsequent heat transport due to radiation and conduction between the particles. Based on the results of the numerical model, the cross sectional area of melted tracks is obtained. The shape of melted tracks is characterized based on the Rayleigh-Plateau capillary instability criterion. The effects of laser scan speed and the laser power on the thickness and shape of the melted tracks are investigated experimentally for both single and multiple layered powder beds. Experimental results are used for validation of the numerical model. The results of this study can be used to determine SLM process windows for metal powders