Strengthening effect of nano-rutile on Ti–3Zr–2Sn–3Mo–25Nb titanium alloy and mechanism of TiO2 phase transformation

Abstract

The safety and stability of medical metal materials in the post-implantation period have always needed to be improved. Ti–3Zr–2Sn–3Mo–25Nb (TLM) near-β bio-titanium alloy has suitable biological properties and nontoxicity, by introducing nano-rutile particles in the micro-arc oxidation surface treatment process of TLM titanium alloy, can enhance its strength performance while retaining the original phase and excellent properties. The effects of nano-rutile on the microstructure and strength properties of micro-arc oxidation coating were tested and analyzed. The results showed that the addition of nano-rutile reduced the porosity and roughness of the coating, significantly increased the thickness, density, and especially the hardness. The self-corrosion potential increased from −0.345 to −0.272 V; the corrosion current decreased from 9.639 × 10−7 to 6.793 × 10−9 A/cm2. Furthermore, the friction coefficient decreased from 0.8 to 0.2, and the strength of fatigue wear and adhesive wear both attenuated. In addition, the chemical reactions that might occur during micro-arc oxidation were also speculated through the phase analysis, and the film-forming process and the influence of rutile doping on the oxidation process were also discussed. Moreover, the model of the nucleus in the TiO2 phase transition process was established and the relationship between the nucleation rate and the temperature was derived.