Investigation on synthesis, pressureless sintering and hot pressing of chromium diboride

Experimental investigations were carried out on synthesis of chromium diboride through boron carbide reduction of Cr2O3. The products obtained were characterized by X-ray diffraction and the process optimized to prepare single-phase CrB2 powder. Densification of CrB2 was investigated by pressureless sintering and hot pressing. A maximum of 93% ρth was obtained by pressureless sintering at 1850 °C after a prolonged duration of 360 min. However, near theoretical density was achieved by hot pressing at 1600 °C and 35 MPa pressure for 2 h. The hardness and fracture toughness of fully dense CrB2 was measured as 22 GPa and 3.5 MPa m1/2, respectively. The mode of fracture in pressureless sintered samples is intergranular whereas that in hot pressed is transgranular.