Multi-physics modeling of direct energy deposition process of thin-walled structures: defect analysis

As a promising additive manufacturing method, direct energy deposition has been widely used to fabricate complex thin-walled parts. However, some defects such as uneven layer surface and excessive build-ups always occur in this process. In this study, a high-fidelity model adopting a novel laser/powder source is developed to simulate the detailed multi-layer deposition process. With layer surfaces being tracked in real-time, laser source model incorporates local incidence angle and defocusing amount to adjust absorbed energy and beam radius on the track surfaces. The powder catchment efficiency varies with the defocusing amount timely. The simulations demonstrate that build-ups are mainly induced by unstable linear powder feed rate and worsen due to laser/powder defocusing and accumulated heat. The layer surface unevenness results from powder positive defocusing, while molten pool dynamics, laser positive defocusing and accumulated heat plays a supplementary role. Eliminating methods are proposed based on the simulations and validated by experiments.