Microstructural characterization of high-carbon ferrochromium

Light optical and scanning electron microscopy techniques were used for high-carbon ferrochromium microstructural analysis. Different microstructures were observed for industrially and laboratory-produced ferroalloys. Primary carbides of M7C3 with chromium ferrite were found in the industrially produced, slowly solidified, and cooled ferroalloy, while primary M7C3 carbides accompanied a eutectic mixture of M7C3 carbides and chromium ferrite in the laboratory-melted and in the water-solidified and water-cooled materials. Different microstructural arrangements are directly related to the friability properties of this material, which characterizes its resistance to abrasion on handling and impact. In ferrochromium upgraded by carbon content reduction, the eutectic M7C3 hexagonal carbides are partly replaced by M23C6 dendritic carbides. The presence of dendritic carbides in the ferrochromium eutectic microstructure can be interpreted as a proof of a lower carbon content, raising the commercial value of the ferroalloy. The hexagonal M7C3 carbides exhibited a central hollow along the longitudinal axis, and on metallographic samples they looked like screw nuts. A model of the solidification mechanism for such crystals is proposed.