Effect of Molybdenum Content on Structure and Properties of a Co-Cr Biomedical Alloy

The present study aimed to develop several Co-Cr biomedical alloys with different amounts of molybdenum. The weight percentages of molybdenum were in the range of 0-4 wt.% in the base alloy (Co-30Cr). The microstructures, phases, density, mechanical strength, wear behavior and corrosion characteristics of these alloys were evaluated. The results showed that density, hardness and compressive strength increased by increase in Mo content in the alloy. In contrast, corrosion rate decreased when the Mo weight percentage was increased. Furthermore, addition of Mo up to 3 wt.% caused the volumetric wear loss to increase. However, 4 wt.% Mo in the alloy led to a reduction in the volumetric wear loss, even lower than that of Co-30Cr alloy without molybdenum. The variations of friction coefficient, however, were different under different operating conditions. Since no single alloy could merely satisfy all the desired characteristics, the entropy–analytic hierarchy process (AHP)–gray relational analysis (GRA) technique was utilized to select the best alloy among the examined materials. From the ranking order gained, it was indicated that M-4 (having 4 wt.% Mo) biomedical alloy possesses the best combination of all the properties.