Thin-Walled, Low-Alloy Steel Structures Produced Through the Gas Carburization of Fully Reduced Metal-Oxide Powder Mixtures

摘要

Studies of the gas carburization of structures made via the reduction of metal-oxide powder mixtures have led to the successful production of thin-walled, low-alloy steels. Thin tape geometries (-200μm final thickness) are produced through the extrusion of metal-oxide powder mixtures. Full reduction and sintering in a 10% H2 atmosphere yields a metal part containing all necessary alloying elements except for carbon. Thin-walled hollow spheres (-50μm wall thickness, -0.9mm diameter) have also been successfully formed through a coating process of similar oxide mixtures. Both geometries have been successfully carburized to reach 4140 steel compositions in a short time. Samples are carburized, post-reduction, at 1000°C in a controlled CO/CO_2 atmosphere in order to avoid metal dusting of the samples. It has been shown in this study that structures with 4140 compositions displaying microstructures comparable to conventionally made steels can be reached in approximately 30 minutes during gas carburization. Additionally, the research shows that carbon contents above the eutectoid composition can also be reached in less than 30 minutes.