High temperature oxidation behavior of a Ni–Co-based superalloy

Oxidation behavior of a Ni–Co-based superalloy prepared by vacuum induction melting (VIM) plus electron beam smelting layered solidification technology (EBSL) and VIM plus electro slag remelting (ESR) at 1180 °C was investigated. The predominant oxides from the outer layer to the inner layer are TiO₂, Cr₂O₃, (Al, Ti)-rich oxide and Al₂O₃, respectively. The (Al, Ti)-rich oxide is considered to be Al₂Ti₄O₉, which is formed by TiO₂ and Al₂O₃. At high temperature, the external oxides experienced significant spalling, particularly in ESR-alloy, which indicated that the EBSL-alloy is more preferable in terms of oxidation resistance. This can be attributed to the presence of finer grains in EBSL-alloy, which facilitates the diffusion of elements and promotes the rapid formation of oxidation scales on the surface of the alloy. Additionally, the presence of a TiO₂ layer cover on Cr₂O₃ reduces the degree of spalling of oxides in EBSL-alloy.