Effects of Y content on the oxidation behavior of CoCrNiAl medium entropy alloys at 1,200°C

Purpose The purpose of this paper is to develop advanced materials with outstanding mechanical properties and high-temperature oxidation performance for their potential application in high-temperature structural components. Design/methodology/approach The alloy ingots with high-purity Co, Cr, Ni, Al and Y metals (= 99.9 Wt.%) were prepared in a vacuum arc melting furnace under an argon atmosphere. Findings This study investigated the impact of the Y content on the microstructure and oxidation behavior of CoCrNiAl medium entropy alloys at 1,200°C. All alloys exhibit a combination of ß and γ phases, with CoCrNiAlY 0.11revealing the presence of obvious sub-micron γ phase precipitates within the ß phase. The oxidation behavior of CoCrNiAlYx (x = 0.05, 0.08, 0.11) at 1,200°C demonstrates the formation of a dense oxide scale on the alloy surface. The surface with aluminum oxide accompanied by yttrium oxide exhibits improved adhesion between the matrix and oxide scale. The CoCrNiAlY0.11 alloy, with a decreased oxidation rate of 7.8 × 10 –6 mg 2 cm −4 s −1 , displays the best oxidation resistance among these alloys with varying Y content. Originality/value The study examines the optimal content of Y in the CoCrNiAl medium alloy and its superior oxidation behavior at 1,200°C.