A strong, wear- and corrosion-resistant, and antibacterial Co–30 at.% Cr–5 at.% Ag ternary alloy for medical implants

A Co–30 at.% Cr–5 at.% Ag alloy was fabricated using a combination of mechanical alloying and spark plasma sintering. The microstructure of the alloy consisted of an ultrafine-grained ε-Co solid solution matrix with an average grain size of 167 nm and uniformly dispersed Ag particles with an average size of 72 nm and a minor amount of nanoscale σ-precipitates with size of 23 nm. Such particular microstructure enabled high hardness of 650 HV and compressive strength of up to 2.3 GPa. Pin-on-disk dry sliding wear tests show that the present alloy exhibited superior wear resistance, with wear rate in the order of 10−5 mm3/(N·m) upon sliding against alumina. The wear-induced microstructure extended only ~500 nm from the sliding surface, with elongated Ag particles. The alloy also demonstrated high resistance to corrosion in artificial saliva solution, due to the formation of a protective passive film. Moreover, the addition of Ag also significantly enhanced the antibacterial activity of Co–Cr alloys, with antibacterial rates against E. coli and S. aureus of 90.5% and 72.6%, respectively. The present alloy with a combination of high strength, superior wear- and corrosion-resistance, and excellent antibacterial activity offers a promising candidate for medical implants. [Display omitted] •An ultrafine-grained Co-30 at.% Cr -5 at.% Ag alloy was fabricated.•The alloy had an ε-Co matrix with nanoscale Cr-rich precipitates and Ag particles.•Dry sliding wear resistance against alumina was evaluated.•Corrosion behavior of the alloy in an artificial saliva solution was investigated.•Addition of Ag significantly enhanced the antibacterial property of Co–Cr alloys.