Abstract
To make clear the feasibility of the plasma carburizing for preparing a functional gradient material, the characteristics of the plasma-carburized layer of Fe-0.15C alloy have been studied. Samples were carburized at the range of temperature from 1173 K to 1273 K for various periods (0.6 ks to 4.8 ks) using plasma of a mixed gas of methane and hydrogen. Microstructural observation, x-ray diffraction examination, and measurement of hardness were conducted. Both analyses of carbon using EPNA and hydrogen using IMA were also carried out on the cross section of some specimens. The main results are as the follows: (1) The plasma carburizing is available for preparing FGM. (2) The profile of hardness is analogous to that of hydrogen concentration rather than that of carbon. (3) The superhardness which shows higher than hardness of the usual quenched sample is attained at inner region where carbon content is lower than that at the specimen surface. Thus, the superhardness results from the effect of hydrogen and carbon.
