COMPOSITIONAL MODULATION OF NEW CO-CR-MO-TA ALLOYS: BIOPHYSICAL DETERMINANTS IN THE EVALUATION OF HEMOCOMPATIBILITY

The performance of Co-Cr-based alloys as permanent implants is governed by their chemical composition and microstructure, which determine the distribution of crystalline phases, surface properties, and the biological interface. This study aimed to develop and characterize Co₆₆Cr₂₈Mo_6−xTa_x alloys (x = 0, 2, 4, 6 wt%), evaluating the progressive substitution of Mo with Ta regarding microstructural and surface properties relevant to hemocompatibility. The alloys were synthesized via arc melting under an argon atmosphere, homogenized at 1000 °C, and metallographically prepared. X-ray diffraction revealed α-Co and ε-Co phases in all compositions, with the emergence of the TaCo₂ intermetallic phase at higher Ta contents, indicating that the solid solubility limit of Ta was locally exceeded. Scanning electron microscopy and energy-dispersive X-ray spectroscopy showed that Tacontaining alloys developed heterogeneous, Ta-enriched surface regions coinciding with TaCo₂ precipitates, whereas the alloy containing only Mo remained uniform. Atomic force microscopy and Kelvin probe force microscopy revealed a non-linear trend in roughness and surface potential. Specifically, the Co₆₆Cr₂₈Mo₂Ta₄ alloy exhibited the highest roughness accompanied by a narrower work function distribution, indicating lower surface electrical heterogeneity. Contact angle measurements confirmed hydrophilic behavior for all compositions. In vitro hemostasis assays demonstrated that this compositional and surface modulation significantly impacts thrombogenicity. Statistical analysis (ANOVA) of the Blood Coagulation Index (BCI) revealed that the alloy with 4% Ta exhibited the highest BCI, statistically significant compared to all other groups, indicating superior resistance to thrombus formation. These combined biophysical correlations suggest that the specific topographic, physicochemical, and electrical surface characteristics achieved with 4% Ta favor an interface with reduced thrombogenic potential. In summary, these results highlight the significant biomedical potential of the customized Co-Cr-Mo-Ta system, specifically the Co₆₆Cr₂₈Mo₂Ta₄ composition, for permanent blood-contacting applications.