Effects of vanadium content on the high temperature oxidation behavior of NbTiZrAlV refractory complex concentrated alloys

Abstract

Oxidation behavior and microstructural evolution of NbTiZrAlV refractory complex concentrated alloys (RCCAs) with vanadium (V) concentration of 3 and 11 at% were investigated at 500 and 800 °C in the air atmosphere. When NbTiZrAlV RCCAs were exposed at 500 °C, the oxidation behavior was controlled by internal oxygen (O) diffusion, and single oxide layer predominating by Ti2ZrO6 and Nb2Zr6O17 were produced after oxidation for 200 h. The mass gains of alloys with 3 and 11 at% V were 0.042 and 0.018 mg/mm2, and corresponding average thickness of oxide layer was 70 and 30 µm. As oxidation temperature was increased to 800 °C, volatilization of V2O5 brought out the aggravation of oxidation degree for NbTiZrAlV RCCA, and complex oxide layers consisting of Nb9VO25, Nb2Zr6O17 and TiO2 were obtained after thermal exposure for 24 h. The mass gains of alloys with the V content of 3 and 11 at% were 1.135 and 0.514 mg/mm2, and the average thickness of oxide layer was 500 and 300 µm, respectively. In both cases, the antioxidant performance of NbTiZrAlV RCCA was significantly improved by the increased content of V. And the enhanced oxidation resistance could be ascribed to the fact that the increase of V addition enhanced the atom diffusion resistance via minimizing mixing enthalpy and maximizing configurational entropy.