Electrochemical Polishing of Extruded and Laser Powder-Bed-Fused Inconel 718
Electrochemical Polishing of Extruded and Laser Powder-Bed-Fused Inconel 718
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DOI：
10.26776/ijemm.06.04.2021.04
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发表时间：
2021-10
影响因子：
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通讯作者：
Srishti Jain;J. Hyder;Mike Corliss;Wayne Hung
中科院分区：
文献类型：
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作者：
Srishti Jain;J. Hyder;Mike Corliss;Wayne Hung
摘要采用电化学抛光（ECP）技术对激光粉末床熔凝（L-PBF）和挤压法生产的Inconel 718合金零件进行亚微米级表面抛光。由于半焊接粉末颗粒、表面缺陷和差异层台阶，L-PBF部件具有非常粗糙的表面，这些通常在挤出和机加工部件的表面上没有发现。本研究比较了这些不同制造的零件在相同条件下的电解抛光结果。钛电极与基于酸的电解液一起使用，以在脉冲电流密度、占空比和抛光时间的不同组合下抛光两个试样。利用数字化三维光学轮廓仪对抛光后的表面质量进行了评估，同时利用光学显微镜和扫描电子显微镜对抛光后的试样进行了显微组织观察。在最佳条件下，ECP成功地将L-PBF部件的表面从17 µm减少到0.25 µm;由于3D打印Inconel 718中微观孔、裂纹、非导电相和碳化物颗粒的去除率不同，进一步抛光并没有改善表面光洁度。挤出材料的微观结构均匀，无加工缺陷，因此可以一致地抛光至0.20 µm。挤压材料的过抛光可以提高其表面光洁度，但由于缺陷和周围的微观应变，L-PBF材料的表面光洁度并不高。
ABSTRACT Electro-chemical polishing (ECP) was utilized to produce sub-micron surface finish on Inconel 718 parts manufactured by Laser Powder-Bed-Fusion (L-PBF) and extrusion methods. The L-PBF parts had very rough surfaces due to semi-welded powder particles, surface defects, and difference layer steps that were generally not found on surfaces of extruded and machined components. This study compared the results of electro-polishing of these differently manufactured parts under the same conditions. Titanium electrode was used with an acid-based electrolyte to polish both the specimens at different combinations of pulsed current density, duty cycle, and polishing time. Digital 3D optical profiler was used to assess the surface finish, while optical and scanning electron microscopy was utilized to observe the microstructure of polished specimens. At optimal condition, the ECP successfully reduced the surface of L-PBF part from 17 µm to 0.25 µm; further polishing did not improve the surface finish due to different removal rates of micro-leveled pores, cracks, nonconductive phases, and carbide particles in 3D-printed Inconel 718. The microstructure of extruded materials was uniform and free of processing defects, therefore can be polished consistently to 0.20 µm. Over-polishing of extruded material could improve its surface finish, but not for the L-PBF material due to defects and the surrounding micro-strain.