Effects of milling and subsequent consolidation treatment on the microstructural properties and hardness of the nanocrystalline chromium carbide powders

The influence of milling and subsequent consolidation treatments on the microstructural properties and hardness of the fabricated Cr₃C₂, Cr₇C₃ and Cr₂₃C₆ ceramic powders are investigated. For this reason, the elemental powders of Cr and C were mixed with proper ratio and then milled to the nanometer crystallite sizes (between 6 and 20 nm) and then were consolidated by using uniaxial cold press and subsequent heat treatment (at 1100 °C for 1 h) in Argon atmosphere. Microstructures of consolidated samples were characterized using X-ray diffraction (XRD) and microhardness measurements. A drastic increase in crystallite size of the samples was observed due to the effect of heat treatment. However, the as-consolidated samples still maintained their nanocrystalline characteristic with an average grain size of less than 100 nm. Besides, a very high hardness of 25 GPa was achieved for the Cr₃C₂ composition. This high hardness is attributed to the formation of carbide phases in the consolidated samples.