研究目的
To investigate the fluid dynamics in melt pools and resultant pore defects in the laser powder bed fusion additive manufacturing process using a novel multi-physics computational fluid dynamics (CFD) model.
研究成果
The study developed a novel powder-scale multi-physics CFD model to understand the physics of keyhole stability and pore generation in the L-PBF process. The model was validated against experimentally measured melt pool dimensions. Key findings include the relationship between melt pool front wall angle and laser line energy density, and the formation of pores at high laser energy density conditions.
研究不足
The model prediction error for melt pool width ranges from 1.3 to 10.6%, while the prediction error for melt pool depth ranges from 1.4 to 15.9%. The small sized pores in the sample, e.g., diameter < 10-20 μm, may not be captured under given CT resolution.
1：Experimental Design and Method Selection:
A novel multi-physics computational fluid dynamics (CFD) model was applied to investigate the fluid dynamics in melt pools and resultant pore defects. Major process physics, such as surface tension, evaporation, and laser multi-reflection, were considered. A discrete element method (DEM) was used to model powder spreading.
2：Sample Selection and Data Sources:
Stainless steel 316L powder material was used, with particle size distribution between 18.77 μm (D10) and 60.30 μm (D90) with a mean diameter of 36.71 μm.
3：77 μm (D10) and 30 μm (D90) with a mean diameter of 71 μm.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: A CW fiber laser with a wavelength of 1070 nm and a focused laser spot size of around 78 μm was used. The substrate was preheated to 150-160°C.
4：Experimental Procedures and Operational Workflow:
Single tracks were fabricated using different laser powers (175 W and 350 W) and speeds (100, 300, 500, and 750 mm/s). The melt pool dimensions were measured and compared with simulations.
5：Data Analysis Methods:
The predicted melt pool dimensions were compared with experimental measurements. X-ray computed tomography (CT) was used to analyze porosity.
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