The effect of temperature and cooling-rate on pack-carburized iron

The pack-carburizing of pure iron was studied for various temperatures in the range of 600 - 950^oC and for various cooling conditions after carburizing. It is observed that at temperatures in the range of 850–950°C, carburized layer is composed of three zones, while the surface microstructure of the specimens carburized at or below 800°C is similar to that of uncarburized iron, and no detectable carburized layer-thickness is observed. In case of carburized-and-quenched specimens, the carburized layer contains martensite of two different morphologies. Among the investigated specimens, the surface hardness is highest (1150 HV_0.3) for the specimen ‘step-cooled’ after carburizing. More carbon uptake in the quenched iron-foils (which were through thickness carburized before cooling) than the furnace cooled foils has indicated the possibility of decarburizing during furnace cooling.