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· At 927 C (1200 K) iron is fcc Austenite
(γ) for which: D(1200) = 1.5 x
10-11 m2 sec-1. This gives a penetration depth
= 2.94 x 10-3 m, for t = 10 hrs.
· At 1200 K the maximum solubility of carbon in Austenite is 1.3
weight %. This limits the surface carbon concentration in Austenite to this
value and makes the process relatively insensitive to carbon carrier gas pressure.
· The surface region will
have second phase Fe3C,
iron carbide, present in the Austenite matrix if
this carbon concentration limit is passed. The iron carbide is a brittle ceramic
phase.
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