Corrosion resistance and corrosion fatigue strength of new titanium alloys for medical implants without V and Al

Abstract

The corrosion resistance and the corrosion fatigue strength of Ti-15Zr-4Nb-4Ta-0.2Pd-0.2O-0.05N and Ti-15Sn-4Nb-2Ta-0.2Pd-0.2O alloys were compared with those of Ti-6Al-4 V extra low interstitial (ELI), Ti-6Al-2Nb-1Ta, pure Ti grade 2 and β 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 was 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 tensile properties of these alloys were measured at room temperature. The 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-4Ta-0.2Pd-0.2O-0.05N alloy at potential up to 5 volt tend to be lower than that of Ti-6Al-4V ELI. Otherwise passive current density of the β type Ti-15Mo-SZr-3Al alloy was higher than that of α + β type alloys. The passive films formed on Ti-15Zr-4Nb-4Ta-0.2Pd-0.2O alloy in the calf serum consisted mainly of TiO 2, ZrO 2, Nb 2O 5, Ta 2O 5 and Pd or PdO as demonstrated using X-ray photoelectron spectroscopy. The cycle to failure of Ti-15Zr-4Nb-4Ta-0.2Pd-0.2O-0.05N and Ti-15Sn-4Nb-4Ta-0.2Pd-0.2O alloys annealed at 973 K for 7.2 ks increased with decreasing applied maximum stress. The fatigue strength at 10 8 cycles in those alloys was about 600 MPa. The fatigue strength of Ti-6Al-2Nb-1Ta alloy at 10 8 cycles was about 700 MPa. The fatigue strength of β type Ti-15Mo-5Zr-3Al alloy at 10 7 cycles was lower than that of α + β type alloys.