High temperature oxidation behavior of Al0.6CrFeCoNi and Al0.6CrFeCoNiSi0.3 high entropy alloys

Amongst the structural materials for high temperature applications that are currently in the focus of research, high entropy alloys (HEAs) exhibit very promising features, such as high strength, good fracture toughness, high temperature phase stabilities and excellent resistance against softening at elevated temperatures. Key influencing factors for high temperature applications are the mechanical properties at elevated temperatures as well as the oxidation behavior of a given material. AlxCrFeCoNi alloys have been mostly investigated among different HEAs. However, up to now there are limited reports dealing with the oxidation behavior of AlxCrFeCoNi-based HEAs, especially with respect to the effect of Si-alloying on the oxidation behavior at elevated temperatures. In this study, the oxidation behavior of two HEAs, Al0.6CrFeCoNi and Al0.6CrFeCoNiSi0.3, were comparatively investigated at T = 800 degrees C, 900 degrees C and 1000 degrees C in air to determine the effect of Si-alloying. The results show that oxidized layers typically consist of Cr2O3/spinet and Al2O3 with an underlying Al-depleted zone. AlN was found inside the Al-depleted zone with the exception of Al0.6CrFeCoNiSi0.3 oxidation at T = 800 degrees C. However, Si alloying only positively influenced the oxidation behavior at T= 800 degrees C. Here, it promoted the formation of a continuous Al2O3 layer. The Si-alloying did not enhance the oxidation resistance at T = 900 degrees C and 1000 degrees C. (C) 2018 Elsevier B.V. All rights reserved.