Enhancement of biological performance of Co–Cr alloys through powder mixed electrical discharge machining

Cobalt–chromium (Co–Cr) alloys are widely used in biomedical implants; however, their surface properties often limit optimal biological performance. This study aims to enhance the biocompatibility of Co–Cr alloy utilizing multi-walled carbon nanotube (MWCNT)-assisted powder-mixed electrical discharge machining (PMEDM). Experiments were designed using a Taguchi L18 orthogonal array by varying discharge current, pulse durations, electrode material, and polarity. The modified surfaces were evaluated through in-vitro hemocompatibility and cytocompatibility tests, along with scanning electron microscopy and energy dispersive X-ray analysis. Results revealed that optimized machining conditions, particularly for sample 13, significantly reduced hemolysis (~ 3.79%) and improved cell viability (~ 92%), compared to the untreated alloy. Surface characterization confirmed the formation of a uniform micro-porous, oxide-rich, and chemically stable layer. The study concludes that MWCNT-assisted PMEDM is an effective surface modification technique for improving the biological performance of Co–Cr alloys, offering strong potential for advanced biomedical implant applications.