Abstract
Pack aluminide coating is a useful method for conferring oxidation resistance on nickel-base superalloys. Nominally, these coatings have a matrix composed of a Ni-Al based B2-type phase (commonly denoted as Β). However, following high-temperature exposure in oxidative envi-ronments, aluminum is depleted from the coating. Aluminum depletion in turn, leads to de-stabilization of the Β phase, resulting in the formation of a characteristic lathlike Β-derivative microstructure. This article presents a transmission electron microscopy study of the formation of the lathlike Β-derivative microstructure using bulk nickel aluminides as model alloys. In the bulk nickel aluminides, the lathlike microstructure has been found to correspond to two distinct components: L10-type martensite and a new Β derivative. The new Β derivative is characterized and the conditions associated with the presence of this feature are identified and compared with those leading to the formation of the L10 martensitic phase. © 1995 The Minerals, Metals & Material Society.
Original language | English |
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Pages (from-to) | 949-956 |
Number of pages | 8 |
Journal | Metallurgical and Materials Transactions A |
Volume | 26 |
Issue number | 4 |
DOIs | |
Publication status | Published - Apr 1995 |
Keywords
- aluminum
- chemical modification
- composition
- derivatives
- martensite
- metallographic microstructure
- nickel Alloys
- oxidation resistance
- single crystals
- superalloys
- transmission electron microscopy
- compositional gradient
- nickel aluminide
- diffusion coatings