Date Approved

7-1-2026

Graduate Degree Type

Thesis

Degree Name

Engineering (M.S.E.)

Degree Program

School of Engineering

First Advisor

Abishek Balsamy-Kamaraj

Academic Year

2025/2026

Abstract

Additive manufacturing (AM) enables the fabrication of complex metallic components but often produces parts with relatively high surface roughness due to layer-wise fabrication and partially fused particles. These surface irregularities can negatively affect mechanical performance, fatigue resistance, and corrosion behavior, making post-processing operations such as electropolishing necessary. This study investigates the electropolishing behavior of additively manufactured and conventionally manufactured 17-4 PH stainless steel using both direct current (DC) and pulsed current (PC) electropolishing. A Box-Behnken Design of Experiments (DOE) was used to evaluate the influence of electrolyte acid ratio, applied current, and initial surface roughness on electropolishing performance of conventionally manufactured 17-4 PH stainless steel. Surface roughness and gloss were measured as the primary response variables, and statistical analysis using response surface methodology (RSM) showed that applied current and initial surface roughness were the most influential parameters affecting final surface quality, while the acid ratio had a smaller effect within the investigated range. The regression model demonstrated strong predictive capability for surface roughness with an R2 value of approximately 0.96 and RMSE of about 0.075 μm. Under optimized conditions (acid ratio=0.51, current=3.4 A, and initial roughness=2.5 μm), DC electropolishing achieved up to 92% roughness reduction, producing a final surface roughness of approximately 0.19 μm for conventional specimens. Pulsed current electropolishing was further evaluated at duty cycles of 25%, 50%, and 75%, with the 25% duty cycle providing the best performance, achieving about 93% roughness reduction and a minimum roughness of about 0.17 μm along with improved surface gloss. Electrochemical characterization using potentiodynamic polarization and cyclic voltammetry was conducted to analyze the anodic dissolution behavior of the electrolyte system. For as-printed AM specimens with roughness near 10 μm, both DC and PC electropolishing reduced surface roughness by approximately 56-58%. When AM samples were pre-conditioned to about 3 μm, electropolishing reduced roughness to about 0.31 μm for DC and 0.26 μm for PC electropolishing. Overall, both DC and PC electropolishing significantly improved the surface finish of 17-4 PH stainless steel, while the achievable polishing performance strongly depended on the initial surface condition of the workpiece.

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Available for download on Tuesday, September 26, 2028

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