Dense and core-rim structured B4C-TiB2 ceramics with Mo-Co-WC additive

B4C-TiB2 ceramics (TiB2 ranging 5 similar to 70 vol%) with Mo-Co-WC as the sintering additive were prepared by spark plasma sintering. In comparison with B4C-TiB2 without additive, the enhanced densification was evident in the sintered specimen with Mo-Co-WC additive. Core-rim structured grain was observed around TiB2 grains. The interface of the rim between TiB2 and B4C phases demonstrated different feature: the inner borderline of the rim exhibited a smooth feature, whereas a sharp curved grain boundary was observed between the rim and the B4C grain. The formation mechanism is discussed: the epitaxial growth of (Ti,Mo,W)B-2 rim around the TiB2 core may occur as a result of the solid solution and dissolution-precipitation between TiB2 phase and the sintering additive. It was revealed that the fracture toughness increased as the content of TiB2 content increased, alongside the decreased hardness. B4C-30 vol% TiB2 specimen demonstrated the optimal combination of mechanical properties, reaching Vickers hardness of 24.3 GPa and fracture toughness of 3.33 MPa.m(1/2).

Automated summary

The addition of Mo-Co-WC sintering additive in B4C-TiB2 ceramics enhances densification and results in core-rim structured grains. The interface of the rim between TiB2 and B4C phases shows smooth and sharp features, suggesting a mechanism involving solid solution and dissolution-precipitation between TiB2 and the additive.