Cu-Ti, Co-Ti and Ni-Ti systems: corrosion and microhardness

Titanium alloys of 10 wt%-72 wt% Cu, 10 wt%-80 wt% Co and 20 wt%-84 wt% Ni were investigated. Ingots were fabricated in a vacuum/argon tungsten arc furnace. The surfaces of the alloys were examined by optical microscopy and SEM/EDS, and the Knoop hardness values of the alloys were measured. The corrosion resistance of the alloys was determined by a potentiodynamic polarization technique in buffered Ringer's solution. When a threshold composition of 30 wt% alloy was reached, a large decrease in corrosion resistance was found to occur. Knoop hardness measurements showed that similar hardness values of approximately 300 KHN can be obtained in all systems with lower alloy content. These values are similar to those obtained with a commercial dental titanium alloy.