A super‐hard high entropy boride containing Hf, Mo, Ti, V, and W

Abstract Super‐hard (Hf,Mo,Ti,V,W)B 2 was synthesized by boro‐carbothermal reduction and densified by spark plasma sintering. This composition was produced for the first time as a single‐phase ceramic in the present research. The optimized ceramic had a single hexagonal AlB 2 ‐type crystalline phase with a grain size of 3.8 µm and homogeneous distribution of the constituent metals. The Vickers hardness exhibited the indentation size effect, increasing from 27 GPa at a load of 9.8 N to as high as 66 GPa at a load of 0.49 N. This is the highest hardness reported to date for high entropy boride ceramics.