Improvement of the mechanical properties of TiB2 for armour applications using different additives and sintering techniques

TiB2 is a promising material in several fields including impact resistant armor, seals, cutting tools, crucibles and wear resistant coatings given its physical, mechanical and chemical properties, in particular thanks to the combination of high hardness and exceptional wear resistance. It is however very difficult to sinter below 2000°C, also under mechanical pressure, and is limited by its low fracture toughness. By using sintering additives, it is possible to improve the sintering process and increase the mechanical properties since the additives react with oxidized layers to form secondary phases. In this study, we explored different preparation methods, various combinations of additives (B4C, Si3N4 and MoSi2), and sintering techniques (hot pressing and pressureless sintering). Thanks to the synergy between optimized process and tailored composition, an almost fully dense material was obtained at 1700°C with hardness of 24.4 ± 0.2 GPa and fracture toughness of 5.4 ± 0.2 MPa m0.5. However, the highest hardness value (30 ± 1 GPa) was obtained for samples sintered by pressureless sintering, featuring a core-shell grain structure.