Tantalum's role in the microstructure and its influence on corrosive behavior in Co-Cr-Ta alloy

• Published in: Journal of alloys and compounds 2025-01, Vol.1010, p.177216, Article 177216
• Main Authors: da Silva Batista, Beatriz, Rodrigues, Samuel Filgueiras, Cardoso, Jorge Luiz, Rodrigues, Maria Veronica Goncalves, de Menezes, Alan Silva, Santos-Oliveira, Ralph, da Silva, Luzeli Moreira, Alencar, Luciana Magalhães Rebêlo
• Format: Article
• Language: English
• Subjects: Alloy corrosion; Cobalt-chromium-tantalum alloy; Microstructure; Volta potential
• ISSN: 0925-8388
• DOI: 10.1016/j.jallcom.2024.177216

Microstructural characteristics strongly correlate with the macroscopic properties of metallic alloy. The present study evaluated the microstructure's local nobility of a novel Co-Cr-Ta alloy for possible biomedical application. The alloy was synthesized by arc melting. X-ray Diffraction, Scanning Electron Microscopy, and Energy-Dispersive X-ray Spectroscopy were applied to characterize the microstructure. Kelvin Probe Force Microscopy, Potentiodynamic Polarization, and Electrochemical Impedance Spectroscopy were used to investigate the influence of cathodic and anodic regions on corrosion. The alloy crystallizes with Co phases (εCo and αCo) with Cr in a solid solution and a TaCo2 phase. The Co phases are distributed in the microstructure, forming a uniform matrix with TaCo2 as the dispersed phase, forming a dendritic microstructure. This configuration allowed the formation of an anodic area for the matrix and a cathodic area for the disperse phase, with a voltage difference between the regions of 654 ±8 mV. Electrochemical tests conducted in simulated body fluid (SBF) revealed the alloy's high corrosion resistance, attributed to developing a protective passive film possibly formed by chromium and tantalum oxides. The dendritic microstructure of Co-Cr-Ta alloy was correlated with the Volta potential distribution and corrosion resistance. Regions abundant in Co and Cr displayed localized susceptibility to dissolution compared to those rich in Co and Ta, suggesting that Ta played a more effective role in enhancing corrosion resistance under these conditions. [Display omitted] •Segregated microstructure provided considerable Volta potential difference.•CoTa structure was resistant to dissolution when compared to CoCr structures.•A significant Volta potential difference promotes corrosion resistance.