| Fabrication and Properties of Reactively Hot Pressed HfB2-HfC Ultra-High Temperature Ceramics |
| Seung-Jun Lee, Young-Hoon Seong, Seung-Su Baek1, Eul-Son Kang1, Do-Kyung Kim |
Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST)
1Agency for Defence Development (ADD) |
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| ABSTRACT |
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$HfB_2$-HfC composites were prepared by reactive hot pressing using Hf and $B_4C$ at temperatures of 1800 and $1900^{circ}C$ for 60 min under 32 MPa in an Ar atmosphere. The reaction sequences of the $HfB_2$-HfC composite were studied through series of pressureless heat treatments ranging from 800 to $1600^{circ}C$. The effect of size reduction of the starting powders on densification was investigated by vibration milling. Fully dense $HfB_2$-HfC composites were obtained by size reduction of the starting powders via vibration milling. The oxidation behaviour of the $HfB_2$-HfC composites at $1500^{circ}C$ in air showed formation of a non-protective $HfO_2$ scale with linear mass gain. Examination of the mechanical properties showed that particle size reduction via vibration milling also led to improved flexural strength, hardness and fracture toughness. |
| Key words:
Reactive hot pressing, Hafnium boride, Hafnium carbide, Ultra high temperature ceramics, Oxidation |
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