Effects of Voltage and Treatment Time on Electrolytic Plasma Polishing of TC6 Titanium Alloy

Electrolytic plasma polishing (EPP) is a noncontact surface-finishing technique for titanium alloys. This study evaluated the effects of polishing voltage and treatment time on TC6 titanium alloy (Ti–6Al–1.5Cr–2.5Mo–0.5Fe–0.3Si). Voltage-gradient experiments were conducted at 260–300 V for 300 s, and time-gradient experiments were conducted at 280 V for 15–900 s. Surface topography was characterized by atomic force microscopy (AFM), morphology and elemental composition by scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDS), and phase behavior by X-ray diffraction (XRD). At a fixed treatment time of 300 s, 280 V produced the lowest measured arithmetical mean height (Sa, 26.39 nm) and the narrowest height-distribution full width at half maximum (65.97 nm) among the tested voltages. At 280 V, Sa and the root-mean-square gradient (Sdq) decreased exponentially with treatment time and approached fitted limits of 26.39 nm and 2.59, respectively. The experimental material removal mass per unit area increased linearly with time at 5.31 × 10⁻⁵ g cm⁻² s⁻¹, with an average current efficiency of 30.24%, and agreed with the Faraday-based model within the measured range. XRD revealed no additional phases after EPP, whereas AFM and SEM showed marked attenuation of grinding grooves and surface protrusions. These results identify 280 V as a favorable voltage within the tested range and quantify the time-dependent smoothing and material removal behavior of TC6 alloy.