Crystallographic dependence of oxidation kinetics and oxidation mechanism on a modified Ni-based superalloy at high temperature

The complex geometries of turbine blades require alloys to deliver excellent overall performance across distinct surface orientations; in addition to mechanical anisotropy, oxidation behavior warrants equal attention. By employing a suite of characterization techniques including XPS, FIB-TEM, and SEM, this study systematically investigates the oxidation behavior and elemental diffusion mechanisms of the second-generation La-modified CMSX-4 superalloy across distinct surface orientations. The results indicate that the comprehensive oxidation resistance ranking of CMSX-4 alloy with three surface orientations is (100) > (111) > (110). During the initial stage of oxidation, the higher proportion of γ' phase on the (100) plane surface leads to the formation of more Al₂O₃ in the alloy surface layer. Additionally, the shorter γ'/γ interface diffusion path on the (100) plane facilitates the diffusion of Al, Ti, and Ta from the matrix to the surface oxide layer, forming a stable oxide layer structure, thereby enhancing the alloy's oxidation resistance. However, in the later stages of oxidation, the higher atomic stacking density of the (111) plane results in superior oxidation resistance compared to the (110) plane. The results can offer a theoretical basis for the manufacturing and service of single-crystal blades with complex shapes.