Simulation of the LPBF Process: Insights into Melt Pool Geometry and Thermal History

From process parameters, to temperature profile, to microstructure and effective mechanical properties: With the rise of Additive Manufacturing (AM) processes, we need to gain a greater insight into a lot of well-known materials (from other processing routes) regarding their mechanical properties.

In established processes, like casting, the cooling rates are typically low (10. K/s) and the resulting microstructure as well as the mechanical properties are typically well known. For the Laser Powder Bed Fusion process (LPBF) the cooling rates are high (up to 107 K/s) and the mechanical properties anisotropic due to the energetically favorable grain growth in build-direction. Since the cooling rate at the phase front (liquid to solid) cannot be directly observed, it is crucial to model the solidification process taking the relevant physical phenomena into account.

The RWTH Aachen Chair for Digital Additive Production DAP developed a model for calculating the melt pool geometry and thermal history for the LPBF process dependent on the process parameters for different materials. First comparisons of the simulation results and the experimentally obtained melt pool geometries have shown deviations < 10 % for Inconel 718, varying laser power and scan speed.