Closed-loop Control of Meltpool Temperature in Directed Energy Deposition
Closed-loop Control of Meltpool Temperature in Directed Energy Deposition
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DOI：
10.1016/j.matdes.2022.110508
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发表时间：
2022-03
期刊：
影响因子：
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通讯作者：
Z. Smoqi;Ben Bevans;A. Gaikwad;J. Craig;Alan Abul-Haj;B. Roeder;B. Macy;J. Shield;Prahalada K. Rao
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文献类型：
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作者：
Z. Smoqi;Ben Bevans;A. Gaikwad;J. Craig;Alan Abul-Haj;B. Roeder;B. Macy;J. Shield;Prahalada K. Rao
这项工作的目的是通过闭环控制熔池温度来减轻粉末和激光定向能沉积（DED）增材制造过程中的缺陷形成。在本研究中，利用同轴双波长成像高温计的反馈信号调制激光功率来控制熔池温度。在实际启发梯形不锈钢零件（SS 316L）的背景下，演示了闭环控制在DED中的应用。我们证明，与在开环条件下制造的零件相比，在闭环控制下制造的零件在孔隙率和均匀微观结构方面的变化减少。例如，加工后表征表明闭环加工零件的体积百分比孔隙率在0.036%至0.043%之间。相比之下，开环加工零件的体积百分比孔隙率变化较大，范围为0.032%至0.068%。此外，用闭环加工构建的零件描绘了一致的枝晶微观结构。相比之下，开环加工的零件表现出微观组织的不均匀性，同时存在枝晶和平面晶粒，这反过来又转化为显微硬度的大变化。
The objective of this work is to mitigate flaw formation in powder and laser-based directed energy deposition (DED) additive manufacturing process through close-loop control of the meltpool temperature. In this work, the meltpool temperature was controlled by modulating the laser power based on feedback signals from a coaxial two-wavelength imaging pyrometer. The utility of closed-loop control in DED is demonstrated in the context of practically inspired trapezoid-shaped stainlesssteel parts (SS 316L). We demonstrate that parts built under closed-loop control have reduced variation in porosity and uniform microstructure compared to parts built under open-loop conditions. For example, post-process characterization showed that closed-loop processed parts had a volume percent porosity ranging from 0.036% to 0.043%. In comparison, open-loop processed parts had a larger variation in volume percent porosity ranging from 0.032% to 0.068%. Further, parts built with closed-loop processing depicted consistent dendritic microstructure. By contrast, parts built with open-loop processing showed microstructure heterogeneity with the presence of both dendritic and planar grains, which in turn translated to large variation in microhardness.