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首页> 外文期刊>International Journal of Machine Tools & Manufacture: Design, research and application >On the role of powder flow behavior in fluid thermodynamics and laser processability of Ni-based composites by selective laser melting
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On the role of powder flow behavior in fluid thermodynamics and laser processability of Ni-based composites by selective laser melting

机译：用选择性激光熔化对粉末流动性在流体热力学和激光加工性的作用

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摘要

A deep understanding of the underlying relation of powder paving and subsequent melting/solidification behavior is critical in predicting and tailoring the processing quality of components fabricated by selective laser melting (SLM) additive manufacturing technology based on the mesoscopic scale. Combining discrete element method (DEM) and finite volume method (FVM), the present work proposed a newly developed three-dimensional DEM physical model coupling with mesoscopic FVM model to give a unique insight into the influence of powder particle size on the flow behavior of powder and resultant melting/solidification characteristics of SLM-processed WC/Inconel 718 composites. The contacting force among powder particles, transition of solid/liquid, and surface tension of melt were considered in the model. By characterizing the packing profiles, velocity vectors and packed state of particles, the simulation results and corresponding experimental validations generally revealed that the powder possessed an elevated flow-ability as increasing the average diameter of powder below 25 mu m, due to the alleviation of the domination of adhesive force among neighboring particles. The considerably high-quality SLM-processed surface without apparent laser-induced defects was obtained with a significantly low surface roughness of 2.2 mu m, attributing to the formation of a denser and more homogeneous powder-bed during SLM. However, when the average diameter of powder particles was elevated over 25 mu m, the combined influence of the elevated gravity of large-scaled powder and the considerable space between neighboring powder particles worsened the flow-ability of powder. The discontinuous and loose powder-bed with a low packing density of particles had a high tendency to produce the top surface with a higher surface roughness, resulting in the formation of a number of defects in SLM-processed parts such as cave-like porosities, balling and discontinuous laser-melted tracks.
机译：深入了解粉末铺路和随后的熔化/凝固行为的潜在关系对于预测和裁缝基于介观标量的选择性激光熔化（SLM）添加制造技术制造的部件的加工质量至关重要。结合离散元件方法（DEM）和有限体积法（FVM），本作采用新开发的三维DEM物理模型耦合与介观FVM模型，以思考粉末粒径对流动性能的影响SLM加工WC / Inconel 718复合材料的粉末和所得熔化/凝固特性。在模型中考虑了粉末颗粒，固体/液体过渡和熔体的表面张力之间的接触力。通过表征包装型材，速度向量和颗粒的填充状态，仿真结果和相应的实验验证通常透露，由于减轻了粉末，粉末具有增加的流动能力，随着粉末的平均直径增加，由于减轻了邻近颗粒中的粘合力的统治。在没有明显的激光诱导的缺陷的情况下，具有2.2μm的显着低表面粗糙度，归因于在SLM期间形成密集和更均匀的粉末床的显着低的表面粗糙度。然而，当粉末颗粒的平均直径升高超过25μm时，大缩放粉末的高升高的重力和相邻粉末颗粒之间的相当空间的综合影响恶化了粉末的流动能力。具有低填充密度的颗粒密度的不连续和松散的粉末床具有高倾向，产生具有更高的表面粗糙度的顶表面，导致在SLM加工零件中形成许多缺陷，如洞穴状孔隙率，球形和不连续激光熔化的轨道。

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