Chemical Forums
Specialty Chemistry Forums => Materials and Nanochemistry forum => Topic started by: tone999 on August 14, 2009, 06:42:35 PM
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A steel is hardened using a high temperature carburising process.
The evolution of the carbon concentration with depth d and time t
is given by the erf function:
cs-cd/cs-co = erf ( d/2 SQRT Dt)
Where, C, Cd and C, respectively represent the concentrations
of the diffusing species at the surface, deep d after time t and in
the bulk. The erf function has the following values:
x erfx
0.3 0.329
0.35 0.379
0.4 0.428
0.45 0.475
0.5 0.520
Consider an initial carbon concentration of 0.15 wt%, if the surface
concentration is suddenly brought to 0.9 wt%, how long will it take
to achieve a 0.6 wt% at a position d=0.2 mm inside the metal?
(Assume a diffusion coefficient of carbon into steel of
2x10^-7 cm^2/s).