Maximum Carbon content on the surface of Mild Steel that is Pack Carburized

Question

Starting from a piece of Mild Steel that is then Pack Carburized, what's the maximum Carbon content that the surface can soak in? Given that we keep it around less than 1000°C and enough time, is it limited to 6.67%, the Carbon content of Cementite?

It would be helpful also if you can describe the depth of penetration of the Pack Carburization, given enough time. Something like:

Casedepth ~ $K \sqrt{time}$,

where K is the Diffusivity constant

Of course, that's wrong as I think there's a limit to the depth considering the alloy, exact temperature and dimension.

Answer 1

I don't know about a computer game, but in the real world max C in the skin is more like 1.5 % with time like 24 hours. Carbide formers like Cr, Mo , will increase that slightly.Also there are trade secrets in the "pack" , alkali metals and earths can facilitate carburization and affect C content. High surface C has few applications so most commercial carburization is done in gases and limits surface carbon to numbers like 0.8 %. Carburization in gas is directly proportional to square root of time . But something else in a pack ( with long times) because some reactants are consumed and not replaced in the pack.