Y/Hf-doped Al0.7CoCrFeNi high-entropy alloy with ultra oxidation and spallation resistance at 1200 °C

Abstract

In this study, a new type of Y/Hf-doped Al0.7CoCrFeNi high-entropy alloy was fabricated and reported. Its oxidation behavior was investigated at 1200 °C compared with the conventional NiCoCrAlYHf alloy. The superior oxidation performance of the Y/Hf-doped Al0.7CoCrFeNi at 1200 °C is attributed to the dramatically enhancing homogeneity of Y/Hf-rich precipitates distribution at phase boundaries resulting from the intrinsic nano-sized phases in the alloy. The improving homogeneity of Y/Hf distribution is beneficial to inhibit the formation of interfacial imperfections and the interfacial S segregation, thus contributing to an enhancing interfacial adhesion and a strong resistance to TGO spallation.

Oxidation Behavior of Alx(CoCrFeNi)100-x High-Entropy Alloys Under Thermal-Cycling Conditions

“…Uniformly distributed grains rich in oxides of Hf and Y were observed on the surface and it was claimed that the oxide growth was controlled by inward diffusion of oxygen -a mechanism much more beneficial for the scales' adhesion than typically reported for HEA outward mechanism [16]. In the next study of the same team [29], the alloy with 15 at.% of Al was further investigated. The material was doped with 0.05 at.% of Y and Hf, followed by oxidation at 1200 °C, showing excellent oxidation kinetics and spallation resistance under isothermal conditions.…”

Influencing factors and mechanism of high-temperature oxidation of high-entropy alloys: A review

“…When the Al content continues to increase, the bcc structure of high-entropy alloy will continue to increase [53][54][55][56][57]. Uporov et al [58] also determined that the bcc phase increases with the anneal time of the AlCoCrFeNiMn high-entropy alloy. Al 0.7 CoCrFeNi alloy with Y/Hf has excellent high-temperature oxidation resistance.…”

Effect of Al content on the oxidation behavior of NiCoCrAlYHf alloys at 1100 ℃

“…The distribution and content of REs have critical effect on the O diffusion rate, as the REs-rich oxides can be the short-circuit path for O diffusion [21]. Meanwhile, the microstructure of NiCoCrAl determined by the composition have important influence on the distribution and solubility of REs [22]. The composition of NiCoCrAlY alloy also play an important role on the Al activity and Al diffusivity [23][24].…”