Influence of electrolyte compositions on structure and high-temperature oxidation resistance of microarc oxidation coatings formed on Ti2AlNb alloy

Microarc oxidation (MAO) coatings have been formed on Ti2AlNb alloy in different electrolytes containing NaAlO2, Na2SiO3 and (NaPO3)(6) solutions, respectively, to evaluate their phase constituents and high temperature oxidation resistance at 800 degrees C. The electrolyte compositions have a significant influence on structure and oxidation resistance of MAO coatings on Ti2AlNb alloy. MAO coatings formed in the electrolytes of NaAlO2 and (NaPO3)(6) solutions, respectively, have a better oxidation resistance than the bared Ti2AlNb alloy after oxidation at 800 degrees C up to 150 h. However, the situation is reversed for the MAO coatings formed in a Na2SiO3 electrolyte, which has a similar weight gain to the bared Ti2AlNb alloy. A compact oxide barrier interlayer of Ti- and Al-containing oxides is found between the substrate and the MAO coatings formed in the NaAlO2 solution, which is effective to protect Ti2AlNb alloy from the inward diffusion of oxygen and the outward diffusion of metallic elements. (C) 2015 Elsevier B.V. All rights reserved.