Microstructure and Mechanical Properties of Heat-Treated Co-20Cr-15W-10Ni Alloy for Biomedical Application

The microstructure and mechanical properties of a heat-treated biomedical ASTM F90 Co-20Cr-15W-10Ni (mass pct) alloy were investigated. The alloy was heat-treated at temperatures of 673 K to 1623 K (400 °C to 1450 °C) for holding times of 0.6 to 259.2 ks. The formation of M₂₃X₆-type (M: metallic element and X: C and N) and η-phase (M₆X-M₁₂X type) precipitates was detected in the heat-treated alloys using a combination of electrolytic extraction and X-ray diffraction. The formation of precipitates deteriorated the ductility of the heat-treated alloys. On the other hand, both the tensile strength and elongation were improved by heat treatment at low temperatures of 673 K to 873 K (400 °C to 600 °C). In this heat-treated alloy, the density of stacking faults was higher than that of the as-received alloy, and the formation of the ε-phase was detected.