Date on Master's Thesis/Doctoral Dissertation

5-2016

Document Type

Master's Thesis

Degree Name

M. Eng.

Department

Industrial Engineering

Committee Chair

Yang, Li

Committee Co-Chair (if applicable)

Depuy, Gail

Committee Member

Depuy, Gail

Committee Member

Jasinski, Jacek

Abstract

Additive Manufacturing (AM) is the next frontier in manufacturing technology, but with this new frontier comes new challenges in post processing techniques. In an attempt to gain further knowledge of the post processing of metal AM components, the Electropolishing (EP) of Electron Beam Melting (EBM), Additively Manufactured Ti- 6Al-4V alloy parts is investigated in the following work. Additive Manufacturing (AM) is predominant in a number of industries, with electronics and consumer goods, aerospace, automotive and medical constituting the majority of AM sales. For most of these, Powder Bed Fusion (PBF) AM technology is of great interest given the ability of PBF to manufacture using metallic materials. Within metal PBF, there are a number of alloys considered most useful for their existing commonality in industry, good compatibility with metal PBF, and principally performance characteristics, with the most popular of these metals being Ti-6Al-4V. Given that many of the intended applications of Ti-6Al-4V parts require good fatigue performance (such as in engine and structural components) and that surface finish is one of the leading limits to fatigue life, the surface finish improvement of AM Ti-6Al-4V a pressing need. Since AM parts inherently contain difficult, if not impossible to reach, features using traditional methods, EP may be vi a promising alternative towards improving surface finish. Of the common metal PBF AM technologies, Selective Laser Melting (SLM) and Electron Beam Melting (EBM), the EP of EBM Ti-6Al-4V parts holds the greatest challenge and greatest reward, as EBM Ti- 6Al-4V parts have a rougher surface finish than SLM Ti-6Al-4V parts, but also contain better resultant performance characteristics than SLM Ti-6Al-4V parts. EP is inherently challenging given the wide range of factors concurrently affecting polishing quality, and even more so a challenge when performed on AM parts. AM parts have a rougher initial surface finish and can be more complex than parts that are typically polished using EP. Gaining proper insight into controlling temperature, time, voltage, electrolyte flow, and other factors such that the uncommonly complex and rough AM part surface can be uniformly leveled and polished is a sizeable task that will take years of careful research. However, laying groundwork in this area, through methodical research and experimentation, has provided a number of valuable insights, pointing future research in the right direction. This work has shown that careful focus must be given to the diffusion layer, surface film, the greatest attribute and also challenge of controlling polish quality in EP. If surface EP proves a viable post processing method for EP, then managing many of the factors effecting EP, including time, temperature, voltage, etc., concurrently must be achieved if metal PBF AM components are to be made as equally useable as existing components.

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