Isothermal oxidation behavior of W‐free Co–Ni–Al‐based superalloy at high temperature.

Co‐based superalloys with the advantages of high melting point, high‐temperature mechanical properties, and large resistance under hot corrosion environment are potential candidates for turbine engine components. The isothermal oxidation behavior of Co–Ni–Al‐based superalloy with the addition of Mo and Cr in dry air at 1073 and 1173 K was investigated. The results showed that similar three‐layer oxides structures were composed of Co‐containing oxides, complex oxides rich in Co and Al, and Al2O3 layer formed on both 2Mo and 2Cr Co–Ni–Al‐based superalloys, and Mo‐containing oxides also existed in the subsurface. The oxides in the outer layer transferred from Co3O4 to denser CoO with the increase in temperature. The γ'‐free zone formed under the Al2O3 layer due to the depletion of Al. Co–Ni–Al‐based superalloys need to conquer a large energy barrier at an earlier stage of oxidation and exhibit good oxidation resistance at 1073 K. [ABSTRACT FROM AUTHOR]