Simultaneous synthesis and consolidation of chromium carbides (Cr3C2, Cr7C3 and Cr23C6) by pulsed electric-current pressure sintering

Chromium carbides (Cr3C2, Cr7C3 and Cr23C6) have been synthesized and consolidated simultaneously from mixtures of Cr and amorphous carbon powders by pulsed electric-current pressure sintering (PECPS). Dense ceramics thus obtained were composed of chromium carbides with a small amount of Cr2O3, which originates from a trace amount of oxygen adsorbed on the as-received starting Cr powder. Synthesis and consolidation processes, which were observed from their shrinkage curves during PECPS, have been examined using X-ray diffraction (XRD) and scanning electron microscopy for the powder compacts. Cr3C2 ceramics sintered at 1300 °C for 10 min under 30 MPa have a 98.9% of theoretical density and fine structures with a 3.6 μm grain size. They exhibit excellent mechanical properties: a bending strength σb of 690 MPa, a Vickers hardness Hv of 18.9 GPa and a fracture toughness KIC of 7.1 MPa m1/2.