Superhard single-phase (Ti,Cr)B2 ceramics

A nominally pure and dense (TiCr)B ceramic was produced by spark plasma sintering of powders synthesized by boro/carbothermal reduction of oxides. The synthesized powders were a single phase and had an average particle of 0.4 ± 0.1 ?m and an oxygen content of 1.2 wt%. Average Vickers hardness values of the resulting ceramics increased from 25.9 ± 0.8 GPa at a load of 9.81 N, to 46.3 ± 0.8 GPa at a load of 0.49 N. Compared to the nominally pure TiB ceramic obtained under the same processing conditions, the (TiCr)B ceramic had higher values under the same load due to the finer average grain size (2.4 ± 1.0 ?m), higher relative density, and solid solution hardening. The results indicated that the Cr addition promoted densification, suppressed grain growth, and improved the hardness of TiB ceramics. This is the first report for dense and single-phase (Ti,Cr)B ceramics as superhard materials.