Spark Plasma Sintering of Superhard B 4 C – ZrB 2 Ceramics by Carbide Boronizing

A carbide boronizing method was first developed to produce dense boron carbide‐ zirconium diboride (“ B 4 C ”– ZrB 2 ) composites from zirconium carbide ( ZrC ) and amorphous boron powders ( B ) by Spark Plasma Sintering at 1800°C–2000°C. The stoichiometry of “ B 4 C ” could be tailored by changing initial boron content, which also has an influence on the processing. The self‐propagating high‐temperature synthesis could be ignited by 1 mol ZrC and 6 mol B at around 1240°C, whereas it was suppressed at a level of 10 mol B . B 8 C – ZrB 2 ceramics sintered at 1800°C with 1 mole ZrC and 10 mole B exhibited super high hardness (40.36 GPa at 2.94 N and 33.4 GPa at 9.8 N). The primary reason for the unusual high hardness of B 8 C – ZrB 2 ceramics was considered to be the formation of nano‐sized ZrB 2 grains.