Ceramic coatings by microarc oxidation of Ti and Al alloys

The influence of niobium carbide (NbC) incorporation on the structure and properties of the Microarc Oxidation (MAO) coatings prepared on Ti alloy and Al alloy was investigated in a solution composed of sodium hexametaphosphate, sodium tetraborate , sodium hydroxide, and sodium silicate. MAO was employed in the based solution with and without the addition of NbC particles. The phase composition and microstructure of the MAO coatings were evaluated using X-ray diffraction and scanning electron microscopy with an energy dispersive spectrometer. In addition, microhardness tester, tribometer , and electrochemical workstation were respectively used to carry out the microhardness, frictional property, and corrosion resistance of the coatings. The MAO coatings obtained on Ti alloy in the solution without NbC particles consisted mainly of Anatase and Rutile TiO 2 , and the oxide coatings on the Al alloy consisted primarily of γ-Al 2 O 3 . Adding NbC particles to the solution improved the forming speed and compactness of the MAO coatings on Ti and Al alloys, and NbC was detected in the coatings through X-ray diffraction. The NbC particles with high hardness and good chemical stability were evenly distributed in the MAO coatings. Therefore, the frictional property and corrosion resistance of the NbC-reinforced MAO coatings are markedly higher than the base oxide coatings on Ti and Al alloys.