The Growth Kinetics of Nickel Aluminide Coatings by the Bi‐velocity Method

Wierzba, Bartek�; Danielewski, Marek; Tkacz–Śmiech, Katarzyna; Sieniawski, Jan

doi:10.1002/cvde.201206999

Cited by 4 publications

(3 citation statements)

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“…A purpose of the present model is to provide a method that simulates the interdiffusion in a multicomponent system. The model is formulated within the bi‐velocity (Darken) method, which is a commonly accepted way of quantifying the Kirkendal effect . The method is based on the postulate that each component's velocity ( υ i ) must be divided into two parts: i) a unique diffusion velocity

(υ_{i}^{d})

, that depends on the diffusion potential gradient and is independent of the choice of a reference frame, and ii) a drift velocity ( υ drift ) that is common for all components and depends on the choice of the external reference frame.…”

Section: Model Of Interdiffusion In a Multicomponent Systemmentioning

confidence: 99%

“…The concentration profiles reproduce the compositions of pure phases and solid solutions with the jumps at the interphase boundaries. In the present approach, the mass transport through the phase boundary zone, and the equilibrium at both interphases of each phase boundary zone, are considered …”

Section: Model Of Interdiffusion In a Multicomponent Systemmentioning

confidence: 99%

“…The objective of this work is to develop a model describing mass transport in the nickel and nickel alloys subjected to aluminization by CVD, and to formulate some basis on which to design the technology. The proposed approach is based on the bi‐velocity (Darken) approach which combines the Darken and Brenner concepts that the volume velocity is essential in defining the local material velocity at non‐equilibrium …”

Section: Introductionmentioning

confidence: 99%

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The solid-state diffusion in binary and ternary systems is overall treated and modeled using the bi-velocity method. The mathematical formulation is given, and the boundary conditions discussed. The model allows the calculation of concentration profiles, spatial distribution of the entropy production rate, and diffusion path. The last two can be used to identify the phases present in the diffusion zone of the ternary system, and determine the thicknesses of the respective layers. The model is applied for the first time to simulate diffusion during aluminization of nickel and its super-alloys, MAR-M200 þ Hf and CMSX-4, and the predictions are compared with the results of the experiments performed by the authors. The results give a new quantitative explanation of the high-active and low-active regimes of aluminization. It is, in particular, confirmed that the high-active and low-active regimes of nickel aluminization can be carried out by a variation of the HCl/H 2 flow ratio. The most important, and a brand new, result concerns the entropy production rate. It is shown that its maxima coincidence with the two-phase zone boundaries in real space, which gives new insight into the modeling of the diffusion in ternary systems.

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