Influence of micro arc oxidation on high temperature oxidation resistance of AlTiCrVZr refractory high entropy alloy

Abstract

In order to inhibit the volatilization of V and improve the high temperature oxidation resistance of AlTiCrVZr refractory high entropy alloy, the micro arc oxidation (MAO) coatings were prepared on AlTiCrVZr high entropy alloy in three different electrolytes: (1) Na2SiO3, (2) Na2SiO3 + (NaPO3)6 + NaOH, (3) Na2SiO3 + (NaPO3)6 + NaOH + Na2B4O7 + KF. The results showed that the MAO coating was relatively smooth and dense in Na2SiO3 + (NaPO3)6 + NaOH + Na2B4O7 + KF, which was better than the other two electrolytes. The MAO coating contained some oxides, such as Al2O3, Cr2O3, SiO2, ZrO2 and TiO2. The high temperature oxidation resistance of MAO coated AlTiCrVZr was improved compared with the uncoated substrate. After oxidation for 5 h, the high temperature oxidation resistance of MAO coated AlTiCrVZr in Na2SiO3 + (NaPO3)6 + NaOH was the best. After oxidation for 20 h, the higher quality MAO coating formed in Na2SiO3 + (NaPO3)6 + NaOH+ Na2B4O7 + KF made the substrate present high temperature oxidation resistance.