On the Formation of Chromium Carbides from Mixture of Chromium Oxide and Graphite in Hydrogen Atmosphere

In order to make clear the formation process of Cr3C2 from a mixture of chromium oxide and solid carbon, the carburization reaction of chromium oxide to Cr3C2 was carried out at temperatures ranging from 1100 to 1500°C in hydrogen stream (500 ml/min).\ oindentThe cross-sections and surfaces of partially carburized pellets were observed by a scanning electron microscope.The results were summarized as follows:(1) The carburization products were Cr3C2, Cr7C3 and Cr23C6. Cr3C2 and Cr7C3 consisted of a single phase were obtained.(2) At the reaction temperature of 1100°C, the yield of Cr3C2 reached 93%.(3) The formed chromium carbides resembled in shape, but they were identified to be Cr3C2, Cr7C3 and Cr23C6.(4) The formed chromium carbides were polycrystalline. The crystal grain in each phase grew up with an increase of the carburization temperature.(5) The formation reaction of chromium carbides was markedly affected by the pressure of CO gas.