Spark plasma sintering of TiN–TiB2 composites

TiN–TiB2 composites were fabricated by spark plasma sintering at 1773–2573 K. Effects of TiN and TiB2 content on relative density, microstructure, and mechanical properties were investigated. Above 2373 K, TiN–TiB2 composites exhibited relative densities over 95%. A high density of 99.7% was obtained at 2573 K with 20–30 vol% TiB2. Shrinkage of the TiN–70 vol% TiB2 composite was the highest at 1573–2473 K. For the TiN–70 vol% TiB2 composite prepared at 1973–2373 K, TiN grains were small, while at 2573 K, TiB2 became a continuous matrix, in which irregular-shaped TiN dispersed. hBN was formed in the TiN–TiB2 composite containing 50–60 vol% TiB2 above 2373 K. The maximum Vickers hardness and fracture toughness obtained for the TiN–80 vol% TiB2 composite sintered at 2473 K was 26.3 GPa and 4.5 MPa m1/2, respectively.