C. Katinas, Y.C. Shin
Keywords: laser powderbed fusion, predictive modeling
Summary:Laser powder bed fusion (L-PBF) has become a popular additive manufacturing process for components where traditional manufacturing techniques are unable to yield favorable microstructures, surface conditions, and/or geometric tolerances. To provide a prediction of the L-PBF process without the need to perform trial-and-error based searching, physical models can be used to determine if adverse conditions will arise based on the process parameters. To predict thermal history, which will govern the resultant microstructure and hence mechanical properties, many approaches using varying level of fidelity have been used. This presentation will report on the comparative assessment on the temperature profiles and cooling rates based on three level of fidelity model: conduction model, thermal model with fluid considered, and fully physics-based high fidelity model. Via benchmarking analysis with experimental results, the accuracies of each approach will be described with the consideration of computational time. Finally, this presentation will report our recent progress in predicting the laser powderbed fusion processes. Two case studies are presented. The first case is to describe the physics of L-PBF during zero-velocity, finite-duration laser energy addition to a Ti-6Al-4V/ Ti-6Al-4V powder bed system during the initial highly transient process of molten pool and keyhole formation. Validation of the model was performed with imagery captured from synchrotron measurements of a static L-PBF process which showed a keyhole welding mode for each of two power settings. The second case is to extension of the model for continuous powderbed fusion of Ti-6Al-4V with the conditions corresponding to EOSINT M270 factory default settings. The physics considered in include volumetric heating of powderbed, free surface motion/tracking, ray-tracing energy addition at free surface, laser beam attenuation through the powderbed, fluid dynamics, evaporation and plasma formation/attenuation. The detailed information on the free surface formation, temperature field, evaporation is presented.