Boundary Conditions
You can model the exchange of carbon with the surrounding environment in different ways. You can apply two types boundary conditions to model the carbon mass transfer. They are of Dirichlet (prescribed carbon concentration) or of Neumann (prescribed carbon flux) types. In the case of a prescribed carbon flux, you have the option of using a thermally activated (Arrhenius type) description for the carbon mass transfer coefficient. By default, the external surfaces of a component have zero flux, which means that they do not transfer any carbon from or to the surrounding environment. The zero flux boundary conditions are replaced by the boundary conditions discussed previously. In a situation where you model selective carburization, you may want to leave parts of the external component surface with a zero carbon flux condition, as this would correspond to partially masking the surface from the surrounding environment.
See
Boundary Conditions
in the theory chapter.
