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Abstract
In recent times, the electro-chemical buffing (ECB) process is being used as a substitute for electro-polishing as it gives a clean and hygienic surface with nano-scale surface finish. This environmentally friendly process finds applications in polishing of ultra-high vacuum systems, niobium SRF cavity and high-purity components. Despite being known over a long time, the process mechanism involving passive layers formation and consequent nano-metric finish generation have not been discussed adequately in the open domain. This article, therefore, focuses on the characterization of ECB process by capturing current-voltage (I-V) relationship as a function of processing parameters. The parametric settings that give the largest passive zone as obtained from the I-V relationship, have been explored in detail using response surface methodology-based experimentation. The I-V characterization shows that the width of passive or constant current region is the largest for 10% concentration of electrolyte, 100 μm inter-electrode gap, 25 LPH flow of electrolyte and 900 rpm of buff-head. A higher surface finish improvement and minimum surface roughness of 30.66 nm is achieved at comparatively moderate concentration and high flow rate of electrolyte, smaller inter-electrode gap and high rotational speed of the buff-head in the ECB process.
NOMENCLATURE
| C | = | Concentration of electrolyte,% (by weight) |
| F | = | Flow rate of electrolyte, LPH |
| G | = | Inter-electrode gap, μm |
| Id | = | Current density, mA/cm2 |
| R | = | Rotational speed of buff-head, rpm |
| RSM | = | Response surface method |
| SI | = | Surface finish improvement, nm |
| V | = | Voltage, V |