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Alumina Grown during Deposition of Thermal Barrier Coatings on NiCrAlY
Author(s) -
Levi Carlos G.,
Sommer Eric,
Terry Scott G.,
Catanoiu Amalia,
Rühle Manfred
Publication year - 2003
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.2003.tb03357.x
Subject(s) - materials science , oxide , dissolution , microstructure , thermal barrier coating , alloy , deposition (geology) , chemical engineering , layer (electronics) , coating , diffusion , metastability , metallurgy , chemical vapor deposition , phase (matter) , diffusion barrier , substrate (aquarium) , electron beam physical vapor deposition , composite material , nanotechnology , chemistry , thermodynamics , paleontology , physics , organic chemistry , sediment , engineering , biology , oceanography , geology
The microstructure of Al 2 O 3 formed by oxidation of a model NiCrAlY alloy during electron‐beam physical vapor deposition of ZrO 2 –7.6 mol% YO 1.5 is examined and compared with that formed on the bare substrate. The growth rate, morphology, and chemical composition of the oxide vary among the different constituents of the alloy surface and are further influenced by the O 2 partial pressure and the physical presence of the thermal barrier coating (TBC) layer. These differences, however, are largely limited to the outer oxide layer. The interplay between the TBC and the growing oxide leads to the formation of a fine‐grain Al 2 O 3 –ZrO 2 “mixed zone” within the thermally grown oxide. A mechanism is outlined to explain this behavior, based on the dissolution of ZrO 2 in a transient Al 2 O 3 structure growing by outward diffusion of Al, and its subsequent reprecipitation when the metastable phase transforms to the stable α‐Al 2 O 3 form.