Anodic dissolution behavior of the complex microstructure of laser directed energy deposited Alloy 718 during electrolyte jet machining in NaCl-ethylene glycol electrolyte
Anodic dissolution behavior of the complex microstructure of laser directed energy deposited Alloy 718 during electrolyte jet machining in NaCl-ethylene glycol electrolyte
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DOI：
10.1016/j.addma.2023.103685
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发表时间：
2023-07
影响因子：
11
通讯作者：
Pengfei Guo;Lin Wu;Xin Lin;Jianfeng Geng;D. Macdonald;Yufeng Zhang;Jianrui Liu;Qiang Wu
中科院分区：
文献类型：
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作者：
Pengfei Guo;Lin Wu;Xin Lin;Jianfeng Geng;D. Macdonald;Yufeng Zhang;Jianrui Liu;Qiang Wu
近年来，利用电化学加工对激光定向能量沉积难切割金属材料进行后处理越来越受到科学和工业方面的关注。如何有效避免复杂微观结构的选择性溶解，提高表面质量是中心问题之一。在本工作中，研究了激光定向能量沉积镍基高温合金718在氯化钠-乙二醇电解液中的微观结构和阳极溶解行为。结果表明，复杂的显微组织由显着的微观偏析诱导产生的γ相、Nb偏析的γ相和第二相组成。在低电流密度下，由于氯化钠-乙二醇溶液中的水含量极少，会出现较弱的二次钝化，导致γ相选择性溶解，从而产生微米级的粗糙表面。然而，高电流密度下形成的过饱和盐膜可以有效地均匀化不同相的溶解速率，从而获得高质量、光滑的表面（Ra 0.53 µm），明显优于 NaCl 水电解质（Ra 1.88 µm）。此外，合适的喷嘴平移速度可通过促进过饱和盐膜的形成并避免杂散腐蚀来显着降低表面粗糙度。这项研究为通过控制复杂微观结构的阳极溶解行为来改善纳米尺度的表面质量提供了见解。
Recently, post-processing of the laser directed energy deposited difficult-to-cut metallic materials using electrochemical machining has drawn more and more attention from both scientific and industrial aspects. How to effectively avoid selective dissolution of the complex microstructure to improve the surface quality is one of the central issues. In the present work, the microstructure and anodic dissolution behavior of the laser directed energy deposited nickel-based superalloy 718 in NaCl-ethylene glycol electrolyte were investigated. The results show that the complex microstructure comprises γ phase, Nb-segregated γ phase and secondary phases, induced by significant micro-segregation. At low current density, weak secondary passivity occurs due to the minimal amount of water in the NaCl-ethylene glycol solution, leading to the selective dissolution of γ phase and thus generating a rough surface on the micrometer scale. However, the supersaturated salt film formed at high current density can effectively homogenize the dissolution rate of the different phases to obtain a high-quality, smooth surface (Ra 0.53 µm) that is distinctly better than that in NaCl-aqueous electrolyte (Ra 1.88 µm). Furthermore, a suitable nozzle translational speed notably decreases surface roughness by promoting the formation of supersaturated salt film and avoiding stray corrosion. This investigation provides insight for improving the surface quality on the nanoscale through controlling the anodic dissolution behavior of the complex microstructure.