ISSN:
1573-4889
Keywords:
Parabolic oxidation
;
diffusion
;
defects
;
Ni-Co alloys
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract The growth of oxide solid solutions on binary alloys has been described using the ternary diffusion model put forward by Wagner and subsequently modified by Dalvi and Coates and Bastow, Whittle, and Wood. A more refined defect model where the presence of all types of vacancy species within the scales is considered has been adapted to obtain the diffusivities of cations in the scales as a function of oxygen potential and cation composition. In addition, correlation effects on cation jump frequencies have been included to account for additional compositional dependence of the diffusivities. Results have been analyzed for oxidation of Ni-Co to (Ni, Co)O at 1273°K in 1 atm oxygen. Improved agreement between calculated and experimental cation concentration profiles indicates that this approach is better than to arbitrarily assign functional forms to the compositional and oxygen activity dependencies of the diffusivities, and demonstrates that an accurate as possible model for the point defect structure of the oxide is required for correct interpretation of the growth of these solid solution types of scales.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00741469
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