Nb2O5/TiO2微弧氧化复合膜层微观组织和高温性能的研究

Investigation of microstructure and high temperature properties on Nb2O5/TiO2 coatings by micro arc oxidation

摘要:

为了研究Ti6Al4V钛合金微弧氧化膜层的抗高温氧化性能,在硅酸钠电解液中添加纳米铌(Nb)颗粒制备了Nb₂O₅/TiO₂复合膜层。采用扫描电子显微镜(SEM)和X射线衍射仪(XRD)分析膜层的微观结构和相组成。实验结果表明：随着纳米Nb浓度增加,膜层表面微孔直径增大、数量减小,膜层中Nb元素含量逐渐增加至5%,膜层厚度由42.28 μm增加至55.48 μm；膜层由锐钛矿型TiO₂、金红石TiO₂、Al₂TiO₅、Nb₂O₅及Nb-Ti化合物组成,金红石型TiO₂峰值和Nb₂O₅峰值逐渐上升；试样增重由基体10.25 mg/cm^₂降低至Nb浓度为6 g/L制备膜层的2.281 mg/cm^₂,平均氧化速率由2.8472×10^_-5 mg.cm^_-2.s^_-1降低至6.3361×10^_-6 mg.cm^_-2.s^_-1；膜层裂纹随Nb浓度增加而减少,有效改善了膜层的抗高温氧化性能。

关键词:微弧氧化，纳米铌，微观组织，高温抗氧化性能

Abstract:

To study the high temperature oxidation resistance of micro arc oxidation coatings of Ti6Al4V titanium alloy, Nb₂O₅/TiO₂ composite coatings was prepared by adding nano-Nb particles into sodium silicate electrolyte. The microstructure and phase composition of the coatings were analyzed by scanning electron microscopy (SEM) and X-ray diffractometry (XRD). The results show that with the increase of nano-Nb concentration, the diameter of micropores on the surface of the coatings increased and the number decreased, the content of Nb increased to 5%, the thickness of the coatings increased from 42.28 μm to 55.48 μm. The coatings were composed by anatase TiO₂, rutile TiO₂, Al₂TiO₅, Nb₂O₅ and Nb-Ti compounds while the peak value of rutile TiO₂ and Nb₂O₅ gradually increased. The weight gain of the sample decreased from 10.25 mg/cm^₂ to 2.281 mg/cm^₂ of the coatings with 6 g/L Nb concentration, the average oxidation rate decreased from 2.8472×10^_-5 mg.cm^_-2.s^_-1 to 6.3361×10^_-6 mg.cm^_-2.s^_-1. The cracks of the coatings decreased with the increasing of Nb concentration, which effectively improved the high temperature oxidation resistance of the coatings.

Key words:micro;arc oxidation, nano;niobium, microstructure, high;temperature oxidation;resistance