Synergistic Effect of Ni and Cu on the Microstructure, Corrosion Properties and Mechanical Properties of As-Cast Biomedical Co-Based Alloy

The microstructure, phase component, corrosion resistance, microhardness, and mechanical property of the as-cast CoCrW-(0 similar to 5)Ni-(1 similar to 4)Cu alloys were investigated to reveal the synergistic effect of Ni and Cu by using X-ray diffraction, scanning electron microscopy, electron probe microanalysis, microhardness tests, and compression tests. The alloys exhibited coarse grains consisting of dendritic substructures. No precipitate was observed in the alloys, but dendritic segregation of Cu in the interdendritic regions and grain boundaries was observed. The phase component of all alloys consists of gamma phase and epsilon phase; the epsilon phase fraction decreased with increasing Ni or Cu content. The corrosion resistance of these alloys decreased with increasing Cu content when the Cu content was greater than 1 wt.%. The addition of Cu or Ni reduced the hardness significantly. The compressive yield strength showed an increasing tendency with increasing Cu content, but the influence of Ni content on compressive yield strength was limited. The results demonstrated that it should be feasible to fabricate a new biomedical CoCrWNiCu alloy by regulating Ni and Cu content, which should be a new development direction of Co-based alloy.