Hi
thanks for good your project. a question.
can it be said that the thickness of diffusion coatings is a multi parameters function?
multi parameters are For example Al activity, Cr, Ti, W, Ta ,...elements activity, carbides, voids .
One has a very useful practical connection between the thickness ''h''' and the diffusion annealing time ''t''; h = SQR( Dchemf . t), where Dchem is the chemical diffusion coefficient, which appears in the Fick's' second law. Dchem depends on the temperature through Arrhenius relationship, also it depends on the chemical composition through their chemical activity coefficients very complicated way:
Dchem = (N2 D*1 + N1 D*2) [1+ dLnGama1/dLnN1]
Where star ''*'' indicates radio tracer diffusivities in homogeneous solid solutions. D*k =M*k RT, M*k is the mobility of kth species. Which may be related to the usual mobility obtained by conductivity measurements with a correlation factor. (Bardeen & Herring).
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