High-temperature oxidation behavior of GTD-111 Ni-based superalloy with an ultrafine-grained surface at 900 °C

The oxidation behavior of GTD-111 Ni-based superalloy with an ultrafine-grained surface (UFGS–GTD111) and its polycrystalline counterpart (CP–GTD111) in Ar + 20% O2 at 900 °C are comparatively investigated. Enhanced presence of high diffusivity paths (namely, GBs and dislocations) on the surface of UFGS–GTD111 significantly increases the diffusion of scale-former elements and oxygen anions toward the oxidation front. A three-layer oxide film (outer Ti-, intermediate Cr- and inner-Al rich) rapidly form on the surface of UFGS–GTD111, and guarantees its better oxidation performance. Grain refinement reduces the critical concentration of Al for forming a virtually continuous alumina layer.