Synthesis and characterization of Cobalt-chromium based alloys via spark plasma sintering for biomedical applications

The present study investigates the impact of Mo and Nb on the characteristics of CoCr sintered alloys, with a specific focus on their potential for biomedical applications. Cobalt-chromium-based alloys (namely, Co-Cr-2.5Mo-2.5 Nb, Co-Cr-3Mo-3 Nb, and Co-Cr-3.5Mo-3.5 Nb) were fabricated using sintering conditions comprising a heating rate of 200 °C/min, pressure of 50 MPa, temperature of 1100 °C, and a dwell period of 15 minutes. The findings indicated that the CoCr alloy, when supplemented with Mo and Nb, exhibited a singular-phase composition consisting mostly of a face-centered cubic (FCC) core comprised of gamma-Co, accompanied by a minor proportion of a hexagonal close-packed (HCP) solid solution matrix known as epsilon-Co, and interspersed with precipitates. The inclusion of Co-Cr-3Mo-3 Nb alloy composition resulted in the highest relative density of 97.56 % compared to other alloy compositions, indicating its optimum alloying properties. The Co-Cr-3Mo-3 Nb alloy had the maximum polarization resistance of 522.52 Ω, indicating a strong resistance to corrosion. Additionally, it displayed the least corrosion rate of 1.5904 mm/year. The ternary alloy consisting of Co-Cr-3.5Mo-3.5 Nb demonstrated superior resistance to the applied indentation stress, as shown by its minimal maximum penetration depth of 372.23 nm and the lowest average coefficient of friction (COF) values.