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

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