Densification and Mechanical Properties of Titanium Diboride with Silicon Nitride as a Sintering Aid

Titanium diboride (TiB 2 ) was hot‐pressed at a temperature of 1800°C, and silicon nitride (Si 3 N 4 ) was added as a sintering aid. The amount of Si 3 N 4 that was added had a significant influence on the sinterability and mechanical properties of the TiB 2 . When a small amount (2.5 wt%) of Si 3 N 4 was added, the Si 3 N 4 reacted with titania (TiO 2 ) that was present on the surface of the TiB 2 powder to form titanium nitride (TiN), boron nitride (BN), and amorphous silica (SiO 2 ). The elimination of TiO 2 suppressed the grain growth effectively, which led to an improvement in the densification of TiB 2 . The formation of SiO 2 also was deemed beneficial for densification. The mechanical properties‐especially, the flexural strength‐were enhanced remarkably through these improvements in the sinterability and microstructure. On the other hand, when a large amount (greaterthan equal to5 wt%) of Si 3 N 4 was added, the mechanical properties were not improved much, presumably because of the extensive formation of a glassy Si‐Ti‐O‐N phase at the grain boundaries.