Synthesis and properties of (Hf,Mo,Ti,W,Zr)B2–(Hf,Mo,Ti,W,Zr)C dual phase ceramics

Dense, dual phase (Hf,Mo,Ti,W,Zr)B2–(Hf,Mo,Ti,W,Zr)C ceramics were synthesized with varying contents of Mo and W. The final (Hf0.317Mo0.025Ti0.317W0.025Zr0.317)C–(Hf0.317Mo0.025Ti0.317W0.025Zr0.317)B2 was a nominally pure, dual phase ceramic, while compositions with higher amounts of Mo and W contained multiple phases. The final microstructures had submicron grains due to pinning effects. Vickers hardness values were up to 48.6 ± 2.2 GPa for an applied load of 0.49 N for the ceramic with optimized composition and densification. The solubility limits for Mo and W into the (Hf,Mo,Ti,W,Zr)B2–(Hf,Mo,Ti,W,Zr)C ceramics were mitigated by decreasing their contents to 2.5 at% each, which produced a nominally pure dual phase ceramic that could be densified by spark plasma sintering or hot pressing. A synergistic hardening effect was observed for optimized ceramic with 5 at% of Mo and W, whereby it had a higher hardness than individual high entropy carbide and high entropy boride phases containing the same transition metals.

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Author Stefano Curtarolo Thomas Lord Department of Mechanical Engineering and Materia ...