Numerical and experimental investigation into gas flow field and spattering phenomena in laser powder bed fusion processing of Inconel 718

Abstract

Accumulated spatters not only deteriorate the quality of the built parts in terms of surface roughness and/or density but also sabotage the whole fabrication process via damaging the powder re-coater. A cross-flow of inert gas inside the processing chamber is by far the only effective mean of removing the spouted spatters from the build platform. Despite the essential role, there are few efforts to investigate the interactions between the cross-flow dynamics and the spouted spatters, and hence, to optimize the design and settings of the cross-flow. Therefore, in this study, a coupled computational fluid dynamics (CFD) – discreate element method (DEM) simulation framework is proposed to study the interactions between the flow field and the spouted spatters during the single scan process. The simulation results for the maximum ejection distance and maximum ejection height of the spatters were shown to deviate from the numerical results reported in the literature by no more than 15%. Moreover, the simulation results for the distribution of the landing sites of the spatters were consistent with the experimental observations, which showed that a large number of large spatters landed near the scan track, while a small number of large spatters landed at a greater distance from the scan track. To the best of the authors’ knowledge, this study represents the first reported attempt to use a coupled CFD-DEM simulation framework to investigate the spatter dynamics within an LPBF chamber and to validate the results with experimental observations and published data. The proposed model is an important tool to optimize and calibrate the cross-flow inside the L-PBF processing chamber.

Keywords

• LPBF
• Gas flow measurement
• Spatter removal
• Coupled CFD-DEM
• High-speed imaging