Determine the carburizing time necessary to achieve a carbon concentration of 0.30 wt% at...

Determine the carburizing time necessary to achieve a carbon concentration of 0.30 wt% at a position 4 mm into an iron–carbon alloy that initially contains 0.10 wt% C. The surface concentration is to be maintained at 0.90 wt% C, and the treatment is to be conducted at 1100°C. Use the diffusion data for g-Fe in Table 5.2.

Table 5.2 A Tabulation of Diffusion Data

aThere are two sets of diffusion coefficients for iron because iron experiences a phase transformation at 912°C; at temperatures less than 912°C, BCC α-iron exists; at temperatures higher than 912°C, FCC γ-iron is the stable phase.

bY. Adda and J. Philibert, Diffusion Dans Les Solides, Universitaires de France, Paris, 1966.

cE. A. Brandes and G. B. Brook (Editors), Smithells Metals Reference Book, 7th edition, Butterworth-Heinemann, Oxford, 1992.

dJ. Askill, Tracer Diffusion Data for Metals, Alloys, and Simple Oxides, IFI/Plenum, New York, 1970.