Carburization is a surface-hardening technique in which carbon is added to the surface of steel at temperatures generally between 850 °C and 950 °C. The case depth of carburized steel is a function of carburizing time and the available carbon potential at the surface. When prolonged carburizing times are used for deep case depths, a high carbon potential produces a high carbon content at the surface, which may result in excessive retained austenite and/or the precipitation of carbides. Both of these have adverse effects on the distribution of residual stress in the case-hardened part. Consequently, a high carbon potential may be suitable for short carburizing times, but not for prolonged carburizing.
The Add-On Diffusion Module (DICTRA) can be used to predict: (i) the carbon profile and case depth as a function of chemistry, time and distance, and (ii) the formation of precipitate carbides, as illustrated in this figure for a martensitic stainless steel.