One of the important features of metal injection molding (MIM) process is its potential to eliminate secondary working operations such as machining. This is hoped to be a suitable production route for hard materials such as martensitic high carbon stainless steels. In this paper, the effects of debinding and sintering atmosphere on the carbon content, and the mechanical properties of heat treated steels have been investigated by using a SUS440C powder. The results were summarized as follows:
(1) The carbon content of both specimens debound in argon and hydrogen was higher than that of the original powder. Thermal debinding in hydrogen produced sound compacts, because the hydrogen gas assisted in the depolymerization of binder from low temperature.
(2) High density and high carbon stainless steel was produced by using hydrogen gas as the sintering atmosphere.
(3) Tensile strength and hardness of the heat treated steels increased with an increase of the sintering temperature. However, the tensile strength of the sintered steels above 1523K abruptly declined because of the precipitation of network of the chromium carbides along the boundaries.