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.