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.
scales
interdiffusion
pore formation
adherence
Diffusion
growth
cyclic oxidation behavior
nickel-aluminides
Transmission electron microscopy
Cavities
sulfur segregation
Vacancy injection
alpha-al2o3
Oxidation
Nickel aluminides
cavity formation
Author
Henrik Svensson
Chalmers
Pavleta Knutsson
Chalmers, Applied Physics, Microscopy and Microanalysis
Krystyna Marta Stiller
Chalmers, Applied Physics, Microscopy and Microanalysis
Oxidation of Metals
0030-770X (ISSN) 1573-4889 (eISSN)
Vol. 71 3-4 143-156Subject Categories
Metallurgy and Metallic Materials
DOI
10.1007/s11085-008-9132-z