Elaboration, microstructure and reactivity of Cr3C2 powders of different morphology

Cr3C2 powders have been prepared by heat-treatment of metastable chromium oxides of controlled morphology in H2CH4 atmosphere. Starting with these highly reactive oxides allows formation of Cr3C2 at 700 °C. The reaction is pseudomorphic and different grain shapes (needles, rods, spheres and polyhedra) have been obtained. The size distribution is narrow and the grain size is generally of the order of a few tens of micrometers, but the “spheres” are in fact made up of aggregates of small platelets about 1.5 μm wide and 0.7 μm thick. The oxidation in air of the carbides was studied by thermal analyses (TGA, DTG and DSC) and was found to proceed in four steps in the 250–700 °C range. The differences observed between the carbides are related to their morphology and texture.