Analytical TEM study of the oxidation of nickel based superalloys

Abstract
The first stages of oxidation of different nickel based superalloys in air environment at 650 °C are investigated, using Transmission Electron Microscopy in association with analytical techniques. The alloys differ in microstructure (polycrystal or single crystal, type of hardening precipitates), and chemical analysis (effect of alloying elements). Ail experiments show evidence of a two oxide layer formation at the surface of the alloy. Different microstructural and chemical changes are demonstrated in the bulk near the metal/oxide interface, leading to a recrystallised band, depleted of hardening precipitates and resulting in a local mechanical softening.