Mitigating keyhole pore formation by nanoparticles during laser powder bed fusion additive manufacturing
Mitigating keyhole pore formation by nanoparticles during laser powder bed fusion additive manufacturing
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DOI：
10.1016/j.addlet.2022.100068
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发表时间：
2022-12-01
期刊：
影响因子：
--
通讯作者：
Chen, Lianyi
中科院分区：
文献类型：
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作者：
Qu, Minglei;Guo, Qilin;Chen, Lianyi
小孔形成是激光金属增材制造工艺中最有害的亚表面缺陷之一。然而，在小孔模式激光熔化期间，仍然缺乏在调谐激光加工条件之外减轻小孔孔形成的有效方法。在这里，我们报告了一种新的方法，以减轻激光粉末床融合（LPBF）过程中，通过使用稳定的纳米粒子的小孔孔形成。产生小孔孔隙的临界小孔深度（即，添加TiC纳米颗粒后，Al 6061的LPBF期间最大锁眼深度（无锁眼孔形成）从246 μ m增加到454 μ m（增加85%）。深入的X射线成像研究和热流体动力学模拟使我们能够确定两种机制共同作用以减轻小孔孔的产生：（1）添加纳米颗粒通过增加液体粘度以阻止突起的发展来防止小孔塌陷;（2）添加纳米颗粒通过增加液体粘度来减缓小孔孔的运动，导致小孔重新捕获孔。我们进一步证明，添加TiC纳米颗粒也可以消除小孔波动引起的小孔气孔在LPBF的Al 6061。我们的研究提供了一种潜在的方法，以减轻小孔孔形成的缺陷精益金属增材制造。
Keyhole pore formation is one of the most detrimental subsurface defects in the laser metal additive manufacturing process. However, effective ways to mitigate keyhole pore formation beyond tuning laser processing conditions during keyhole mode laser melting are still lacking. Here we report a novel approach to mitigate keyhole pore formation during laser powder bed fusion (LPBF) process by using stable nanoparticles. The critical keyhole depth for keyhole pore generation (i.e., the largest keyhole depth without keyhole pore formation) during LPBF of Al6061 increases from 246 & mu;m to 454 & mu;m (85% increase) after adding TiC nanoparticles. In-depth x-ray imaging studies and thermo-fluid dynamics simulation enable us to identify that two mechanisms work together to mitigate keyhole pore generation: (1) adding nanoparticles prevents the keyhole from collapsing by increasing the liquid viscosity to impede the protrusion development; (2) adding nanoparticles slows down the keyhole pore movement by increasing the liquid viscosity, resulting in the recapturing of the pore by the keyhole. We further demonstrate that adding TiC nanoparticles can also eliminate the keyhole fluctuation induced keyhole pore during LPBF of Al6061. Our research provides a potential way to mitigate keyhole pore formation for defect lean metal additive manufacturing.