Oxidation response of a vacuum arc melted NbZrTiCrAl refractory high entropy alloy at 800–1200 °C

Abstract An equimolar refractory high-entropy alloy NbZrTiCrAl was prepared by vacuum arc melting, the microstructure and oxidation response of the alloy at 800 °C, 1000 °C and 1200 °C were investigated. The alloy mainly consists of BCC single-phase solid solution and shows an inhomogeneous microstructure with dendritic and inter-dendritic regions. The oxidation of the alloy at 800 °C and 1000 °C follows parabolic rate law, and the protection performance can be attributed to the formation of dense and homogenous complex oxides scale composed of CrNbO 4 , ZrO 2 , TiO 2 , Al 2 O 3 and ZrNb 2 O 7 . The linear oxidation kinetics of the alloy at 1200 °C is observed, the scale composed of similar oxide products but with layered structure is probably the reason of the poor resistance to long-term oxidation at higher temperatures. The formation of the oxide scale and the oxidation-resistant mechanism of the alloy at different temperatures have been discussed.