An Investigation on Refining Electrochemical Polishing of Laser Cut CoCr L605 Struts for Precise Material Removal and Minimal Roughness

The optimization of electrochemical polishing (ECP) of CoCr L605 alloy tubes, specifically for stent applications, holds significant potential for enhancing the performance of medical devices. The current study presents a systematic approach to refining ECP parameters to achieve controlled material removal and optimal surface smoothness. A design incorporating three struts of varying thicknesses within a short tubular section was then manufactured on a CoCr L605 tube of outer diameter of 1.6mm and wall thickness of 110 microns, using the Starcut Femto laser cutting machine. All the fabricated samples were immediately cleaned after manufacturing using a meta cleaning solution. Subsequently, the samples were polished using a custom-made polishing setup using the direct current source and a carefully formulated electrolyte solution. The experimental conditions were systematically varied to thoroughly investigate the impact of various polishing parameters onto the polishing process. Key polishing variables selected for the analysis included voltage, temperatures, and sample dip time. The distance between the anode and the cathode was kept constant for the polishing process. The Taguchi L9 orthogonal array method was employed to design the experiments (DOE), facilitating a comprehensive analysis of how these parameters influence the electrochemical polishing process of CoCr L605 material. Post-polishing assessments of the samples focused on investigating the strut width reduction, uniformity in polishing, and surface roughness, utilizing high-resolution microscopic imaging for detailed analysis and atomic force microscopy (AFM). The results indicated that the reduction in strut width increased as the dip time, temperature, and applied voltage were raised, indicating a higher material removal rate with dip time being the most significant factor influencing the material removal rate. While higher voltage and extended polishing time significantly enhanced material removal rates, temperature variation showed a comparatively moderate influence on strut width reduction, indicating a complex interplay between thermal effects and the electrochemical polishing process. The microscopic image analysis revealed uniform polishing with negligible defects. Moreover, the AFM results demonstrated that surface roughness was consistently minimal across all conditions, ensuring a high-quality finish. The present optimization study provides critical insights into parameter modulation for precise control over the ECP process, advancing the fabrication of CoCr stents with superior surface integrity and consistent dimensional characteristics. The findings underscore the efficacy of the proposed chemical composition for polishing and experimental design, paving the way for further advancements in biomedical material processing for stent application.