The Behavior of Al_0.5CoCrFeNiCuPt_0.3 High-Entropy Alloy During High-Temperature Oxidation

The quest for high-entropy alloys (HEAs) with superior resistance against oxidation at elevated temperatures is one of the urgent problems in materials society, since HEAs are candidates for coating machinery parts operating in aggressive conditions (such as turbine blades, turbojet and jet engines, etc.). In this study, the effect of minor platinum alloying on the microstructure, phase composition and high-temperature oxidation resistance of Al_0.5CoCrFeNiCuPt_0.3 HEA was studied. It was demonstrated that platinum does not precipitate as an intermetallic phases; rather, it dissolves in the solid solution phases. High-temperature oxidation tests were carried out in a muffle furnace at 900 °C and 1000 °C for 50 h in air. It was found out that platinum alloying significantly increases oxidation resistance of Al_0.5CoCrFeNiCuPt_0.3 HEA at elevated temperatures with specific weight change of 0.139 mg/cm² and 0.238 mg/cm² after 50 h of isothermal exposure to 900 °C and 1000 °C, respectively. A dense oxide layer, mainly composed of Al₂O₃, without defects and pores protected the surface of the alloy.