PACK CARBURISING

Pack carburization is the oldest method among the case hardening treatments and sufficient attempts has not been made to understand this process in terms of heat and mass transfer, effect of alloying elements, dimensions of the sample, etc. Thus, a two dimensional mathematical model in cylindrical co-ordinate is developed for simulating pack carburization process for chromium bearing steel (a ternary system (Fe-C-Cr)) in this study.

Heat and mass balance equations are solved simultaneously where surface temperature of the sample varies with time, but the carbon potential at the surface during the process remains constant. Fully implicit finite volume technique is used to solve the governing equations. A good agreement has been found between the predicted and published data.

Key Research Findings

Two dimension analysis provides better description of the process than one dimension
The effect of second dimension is significant especially in predicting the case depth near the corners of the sample
Neglecting the second dimension may provide wrong interpretation and affect the operating life of the specimen
As the size of the sample increases, the case depth is decreased
Thin layer of charcoal packing increases the case depth

Figure 1: Comparison between computed and published experimental temperature data

Figure 2: Computed carbon concentration profile within the specimen at 1173 K for 6 hours (high C concentration at the corner is evident)

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