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

Abstract

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.

Coarsening Evolution of γ′ Phase and Failure Mechanism of Co-Ni-Al-Ti-Based Superalloys During Isothermal Aging

“…Beforehand, Ni-based superalloys are the most successfully applied superalloys in this field (Pandey et al, 2021). Due to the not quite high melting point, improvement in the high temperature bearing capacity of Ni-based superalloys is severely restricted (Gao et al, 2021c;Xu et al, 2021a;Xu et al, 2021b). Traditional Co-based superalloys are dependent on solution strengthening and carbide strengthening, and lack of ordered L1 2 -γ′ phase precipitation strengthening widely present in Ni-based superalloys, which results in poor mechanical properties at high temperatures (Feng et al, 2021;Lu et al, 2021).…”