The oxidation behavior of Ni2FeCoCrAlx high-entropy alloys in dry air

The oxidation behavior of three Ni2FeCoCrAlx high-entropy alloys (where x = 0, 0.5, and 1.0) was studied at 600-900 degrees C in dry air. The oxidation kinetics of all the alloys obeyed the parabolic rate law at T >= 700 degrees C, with their oxidation rates steadily increasing with either increasing temperature or decreasing Al content. Discontinuous oxide particles grew on the alloys at 600 degrees C, while multiple layered scales and an exclusive Al2O3 layer formed on the Al-free and the Al-containing alloys, respectively at T >= 700 degrees C. In addition, an internal nitrogen attack to form AIN was also observed for the Al-containing alloys at 900 degrees C. (C) 2020 Elsevier B.V. All rights reserved.