Oxidation behaviour of eutectic refractory high-entropy alloys at 800–1000 °C

Herein, we investigated the oxidation behaviour of B2/C14 Laves phase hypoeutectic Al23Cr20Nb15Ti32Zr10, eutectic Al28Cr20Nb15Ti27Zr10, and hypereutectic Al33Cr20Nb15Ti22Zr10 (at%) refractory high-entropy alloys (RHEAs) at 800–1000 °C. An increase in the Al/Ti ratio reduced the mass gain, but induced an oxide scale spallation. Before spallation, the studied alloys demonstrated better oxidation resistance than the current Al-Cr-Nb-Ti-(V)-Zr RHEAs at 800 °C. An analysis of the Al23Cr20Nb15Ti32Zr10 alloy with near-parabolic oxidation kinetics revealed the formation of an external oxide layer with a dominant TiO2 and an internal reaction zone comprised O-rich products and TiN. The oxidation mechanisms and suggestions for improving the oxidation/spallation resistance were discussed.