Formation and Healing of Voids at the Metal-Oxide Interface in NiAl Alloys
Journal article, 2009
The present investigation concerns the formation and healing of voids at the metal-oxide interface in beta-NiAl alloys. It is shown that transient cavities form at the metal-oxide interface during the initial stage of isothermal oxidation at 1,050 A degrees C. These voids disappear after a few hours of oxidation, due to their filling with oxide. It is proposed that the filling of the transient voids occurs through cracks in the outer oxide scale. This allows for an oxygen transport into the cavities where a new oxide is created and grows outwards from the metal surface. Pt-containing beta-NiAl alloys that have better resistance to oxide spallation show suppressed formation of cavities and/or a faster filling of voids. This is explained by the enhanced diffusion of Al in these materials.
cyclic oxidation behavior
Transmission electron microscopy