Oxygen diffusion hardening of Ti-Nb-Zr alloys

Ti-13Nb-13Zr (Ti-13-13(TM)) is a new titanium alloy developed for medical implant applications. In the oxygen diffusion hardened condition, Ti-13-13 and titanium alloys which possess zirconium, are hardenable at temperatures of 400 to 600 degrees C with the end result being a passive, mechanically stable, abrasion resistant oxide ceramic surface layer of about 0.2 to 2 mu m in thickness. The thickness of this surface layer depends on the concentration of zirconium, time, temperature, and partial pressure of oxygen. This paper describes the results of x-ray diffraction analysis, secondary ion mass spectroscopy, x-ray photoelectron spectroscopy, Knoop and Nano hardness measurements, and reciprocal polarization resistance measurements of hardened Ti-13-13, and selected Ti-Nb-Zr alloys. The results of this work suggest that zirconium plays a key role for effective oxygen diffusion hardening at 500 degrees C for Ti-13-13 and similar Ti-Nb-Zr alloys.