Research On The Preparation And The Properties Of Ti13Nb13Zr Alloy’s Thermal Oxide Layer

Ti13Nb13Zr alloy is biological titanium alloy, which with high strength, high toughness, high fatigue strength and good biocompatibility. The application of Ti13Nb13 Zr alloy is restricted in the field of artificial joints as its low surface hardness and poor wear resistance. Under high temperature, oxygen can be dissolved in titanium alloy, which can make the effect of solid solution strengthening. In this paper, the technology of thermal oxidation was used to improve the performance of Ti13Nb13 Zr alloy. The surface composition, surface morphology, mechanical properties, electrochemical corrosion, wettability and biotribological properties of the thermally oxidized Ti13Nb13 Zr alloy were analyzed to evaluate the performance of the thermally oxidized Ti13Nb13 Zr alloy.It was found that the main composition of the thermal oxide layer was the rutile type of Ti O2. With the increasing of the temperature, the thickness of the oxide layer was increased from 2.19 μm to 288.50 μm and the hardness of the Ti13Nb13 Zr alloy was improved greatly. In addition, when the temperature was 900℃, the hardness of the Ti13Nb13 Zr alloy reached 1038 HV,which was 4.47 times as large as the original sample. With the increasing of the oxygen content in volume, the thermal oxide layer was from 40.52 μm to 51.72 μm and the hardness of the Ti13Nb13 Zr alloy was also improved greatly. Moreover, when the oxygen volume content was 40%, the hardness of the Ti13Nb13 Zr alloy was 1038 HV, which was the maximum one. Meanwhile, with the increasing of the thermal oxidation time, the surface hardness of Ti13Nb13 Zr alloy was at around 1000 HV. The Nano-hardness of the Ti13Nb13 Zr alloy was also improved after the thermal oxidation. When the temperature was 800℃, the Nano-hardness of the Ti13Nb13 Zr alloy was 16.37 GPa, which was 3.76 times as large as the original sample.With the thermal oxidation time from 2 hours to 10 hours, the oxidation weight curve of Ti13Nb13 Zr alloy was in accordance with the regular of the linear oxidation kinetics. The oxide growth rate was proportional to the thermal oxidation time. The thermal oxidation rate constants of 700℃, 800℃, 900℃ and 1000℃ were 0.222 mg2·cm-4·h-1, 0.488 mg2·cm-4·h-1, 48.003 mg2·cm-4·h-1, 664.914 mg2·cm-4·h-1, respectively. With the increasing of the temperature, the thermal oxidation rate constant of Ti13Nb13 Zr alloy increased and the Ti13Nb13 Zr alloy oxidation resistance decreased.Additionally, the contact angle and the adhesion work of the Ti13Nb13 Zr alloy were reduced after it was thermally oxidized. The wettability of Ti13Nb13 Zr alloy was improved greatly with the thermal oxidation. When the thermal oxidation time was 4 hours, the temperature was 900℃ and the oxygen volume content was 40%, the contact angle of Ti13Nb13 Zr alloy was 68.50°, much closer to the optimal water contact angle for cell adhesion of 70°. At the same time, the corrosion resistance of the Ti13Nb13 Zr alloy was improved after the treatment of thermal oxidation. When the thermal oxidation time was 4 hours, the temperature was 900℃ and the oxygen volume content was 40%, the Ti13Nb13 Zr alloy’s corrosion potential was-0.1902 V and the corrosion current was 1.658×10-9 A/cm2 and the corrosion depth was 0.14×10-4 mm/a. And at this condition, the Ti13Nb13 Zr alloy’s corrosion resistance was the best one. Biological tribology experiment certificated that the wear resistance of Ti13Nb13 Zr alloy had been greatly improved as the existence of the thermal oxide layer.