Y-Hf co-doped AlCoCrFeNi2.1 eutectic high-entropy alloy with excellent oxidation and spallation resistance under thermal cycling conditions at 1100 °C and 1200 °C

Highlights: • The oxidation rate of Y-Hf co-doped AlCoCrFeNi_2.1 EHEA is much lower than that of NiCoCrAlYHf alloy. • The Y-Hf co-doped AlCoCrFeNi_2.1 EHEA exhibits a strong scale interfacial adhesion at 1100 °C and 1200 °C. • The Y-Hf co-doped AlCoCrFeNi_2.1 EHEA shows a highly structural stability after prolonged oxidation at 1100 °C and 1200 °C. • The Y-Hf co-doped AlCoCrFeNi_2.1 EHEA might be a promising candidate as the oxidation-protective overlay coating material. The oxidation behavior of AlCoCrFeNi_2.1 eutectic high-entropy alloy (EHEA) with Y-Hf co-doping under thermal cycling conditions at 1100 °C and 1200 °C is studied in comparison to the conventional NiCoCrAlYHf alloy (CNA). The oxidation rates of EHEA at two temperatures are much lower than those of CNA. Additionally, the resistance to Al₂O₃ scale spallation for the EHEA is much superior to that for the CNA. It is well demonstrated that increasing the interfacial toughness is more beneficial to improve the scale spallation resistance in comparison to the decrease in oxidation rate.