Electrochemical-Based Surface Enhancement of Additively Manufactured Ti-6Al-4V Complex Structures Haniyeh Fayazfar, Issa Rishmawi, and Mihaela Vlasea Submitted: 18 August 2020 / Revised: 22 December 2020 / Accepted: 16 January 2021 / Published online: 3 February 2021 Poor surface quality has long been a significant challenge to the broad adoption of additive manufacturing (AM) in industry. This work deploys a customized electropolishing (EP) procedure to improve the surface finish of complex laser powder bed fusion Ti-6Al-4V parts with internal channels and various geometries using a substantially less hazardous, anhydrous, alcoholic solution, while maintaining the geometrical fidelity of the parts. A preliminary study on simple geometries was run to evaluate the effect of EP time on surface roughness and thickness loss of a part. By using a customized test setup and an artificial EP waveform to accurately control EP parameters, a high EP efficiency was achieved (maximum reduction of surface roughness up to 70% and a minimum thickness loss of 11%) with low treatment times. Subse- quently, EP was conducted on the internal surfaces of various geometries in increasing order of complexity; the results showed the effectiveness of the proposed technique across different geometrical features, leading to maximum uniform surface roughness improvement of 77% with minimum thickness loss of only 7%. The proposed methodology from this work for a fast and cost-effective surface enhancement methodology in an environmentally safe solution may be used on real, complex AM parts to enhance both internal and external surface quality. Keywords additive manufacturing, laser powder bed fusion, electropolishing, Ti-6Al-4V, surface topography, surface quality enhancement 1. Introduction Although additive manufacturing (AM) technolo- gies—specifically laser powder bed fusion (LPBF)—are now well accepted as disruptive in the design and manufacturing of high-performance parts, there are significant barriers to its broad industrial adoption. Among the barriers, poor surface quality has long been a crucial challenge as it may impact functional properties of a part, including mechanical response, heat transfer, fluid flow and biological integration (Ref 1). As discussed in Ref 2, the high as-built surface roughness of LPBF parts can negatively affect mechanical performance, further justifying the need for surface enhancement of the parts. Therefore, requirements for surface properties in AM products have seen more interest in recent years (Ref 3–7). There are various phenomena inherent to the LPBF process that create surface topography fluctuations, all of which are dependent on the surface orientation (Ref 8). Such phenomena include and are not limited to material ejections and spatter (Ref 9), balling effects (Ref 10), the staircase effect and partially bonded particles (Ref 11). These surface topography imperfections serve as stress concentration and fatigue crack initiation sites that are detrimental in many applications in the aerospace, automotive and biomedical sectors (Ref 7, 12–14). To improve surface quality of as-printed parts, most researchers so far have focused on optimizing the printing process, such as changing the contour track and up-skin, surface re-melting, using fine powders and also optimizing the controllable process parameters (Ref 15–18). However, process refinement alone cannot completely overcome surface imper- fections, as the laser powder interaction physics itself becomes the limiting factor in terms of surface topography performance. Post-process treatments have therefore been used to further enhance surface quality and dimensional accuracy of AM parts (Ref 19). Conventional, non-chemical post-processing tech- niques including machining (Ref 20, 21), mechanical polishing (Ref 22) and abrasive flow polishing (Ref 23) may be impractical for AM parts that have fine features, internal cavities, heat- or stress-sensitive materials, multilayered sys- tems or systems with controlled porosity (Ref 22–24). In addition, such methods can be expensive, and the AM post- processing workflow can benefit from more cost-effective methods to address finishing of complex surfaces. Electro- chemical surface treatment methods can access internal and complex surfaces, since the fluid electrolytes can flow into intrusions and access hidden component faces. Therefore, in principle, electropolishing (EP) can be used to selectively smoothen surface features and improve surface roughness (Ref 6, 26). Several attempts have been made to enhance the surface quality of powder bed fusion Ti-6Al-4V parts using EP (Ref 5, 6, 25, 26). Generally, there is a gap in available literature for a reliable approach for EP of internal surfaces and cavities of AM parts, which normally requires precise control of the EP conditions. In a previous work, an innovative EP method was utilized to effectively improve the internal surface roughness of Inconel 625 parts with various geometries made through LPBF Haniyeh Fayazfar, Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON N2L 3G1, Canada; and Department of Mechanical and Manufacturing Engineering, University of Ontario Tech, Oshawa, ON L1G 0C5, Canada; and Issa Rishmawi and Mihaela Vlasea, Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON N2L 3G1, Canada. Contact e-mail: ramona.fayazfar@ontariotechu.ca. JMEPEG (2021) 30:2245–2255 ÓASM International https://doi.org/10.1007/s11665-021-05512-x 1059-9495/$19.00 Journal of Materials Engineering and Performance Volume 30(3) March 2021—2245