A geometry-based comprehensive heat source model for FE thermal simulation of laser directed energy deposition

Abstract

Laser Directed Energy Deposition (L-DED) is a distinctive manufacturing process known for its relatively high deposition rate, minimal waste, and ability to make complex geometries. Accurate prediction of the temperature distribution and thermal history during L-DED is crucial for estimating the microstructure, porosity, and mechanical properties of the fabricated parts. However, existing analytical and numerical models often fall short in accuracy due to overlooking the geometrical characteristics and shape of the deposition. To address this issue, a multi-step statistical/numerical analysis workflow is proposed to elucidate the thermal responses in L-DED deposited tracks. First, a data-driven predictive model using statistical methods was used to estimate the deposition geometry based on the key process parameters which are laser power (P), powder feed rate (F), and scanning speed (V). Next, the prediction results were implemented in a dynamic hybrid quiet/inactive elemental control scheme to capture the deposition process. Further, activated elements are subsequently analyzed thermally through a transient 3-D finite element (FE) heat source model accounting for heat flux from conduction, convection, and radiation. The laser beam’s energy follows a two-dimensional Gaussian distribution, while the heat flux over the actual deposition region, modeled as a quarter-ellipsoid with the predicted geometrical characteristics. This representation captures the actual projection of the laser beam on the deposition. The simulated melt pool depths and temperature showed excellent agreement with experimental measurements for L-DED depositions of Inconel 625 superalloy, exhibiting less than 10% deviation, thereby validating the proposed heat source model.