CORROSION-RESISTANCE AND CORROSION-FATIGUE STRENGTH OF NEW TITANIUM-ALLOYS FOR MEDICAL IMPLANTS WITHOUT V AND AL

The corrosion resistance and the corrosion fatigue strength of Ti-15Zr -4Nb-3Ta-0.2Pd-0.20-0.05N and Ti-15Sn-4Nb-2Ta-0.2Pd-0.20 alloys were c ompared with those of Ti-6Al-4 V extra low interstitial (ELI), Ti-6Al- ZNb-lTa, pure Ti grade 2 and beta type Ti-15%Mo-5Zr-3Al alloys. Anodic polarization and corrosion fatigue testings were performed in various physiological saline solutions at 310 K. The corrosion fatigue test w as carried out under the condition of a tension to tension mode with a sine wave at a stress ratio of 0.1 and at a frequency of 10 Hz. The t ensile properties of these alloys were measured at loom temperature. T he change in current density was small up to passivity zone in 1 wt.%, lactic acid. PBS(-), calf serum and eagle's MEM + fetal bovine serum solutions except 5 wt.% HCl. The current density of Ti-15Zr-4Nb-41a-0. 2Pd-0.20-0.05N alloy at potential up to 5 volt tend to be lower than t hat of Ti-6Al-4V ELI. Otherwise passive current density of the beta ty pe Ti-15Mo-5Zr-3Al alloy was higher than that of alpha + beta type all oys. The passive films formed on Ti-15Zr-4Nb-4Ta-0.2Pd-0.20 alloy in t he calf serum consisted mainly of TiO2. ZrO2, Nb2O5, Ta2O5 and Pd or P dO as demonstrated using X-ray photoelectron spectroscopy. The cycle t o failure of Ti-15Zr-4Nb-41a-0.2Pd-0.20-0.05N and Ti-15Sn-4Nb-4Ta-0.2P d-0.20 alloys annealed at 973 K for 7.2 ks increased with decreasing a pplied maximum stress. The fatigue strength at 10(8) cycles in those a lloys was about 600 MPa. The fatigue strength of Ti-6Al-2Nb-1Ta alloy al 10(8) cycles was about 700 MPa. The fatigue strength of beta type T i-15Mo-5Zr-3Al alloy at 10(7) cycles was lower than that of alpha + be ta type alloys.