Advanced tungsten-based ceramics achieve high hardness and ablation resistance

A research team successfully synthesized tungsten carbide (WC) and tungsten boride (WB₂) ceramics with excellent mechanical properties and ablation resistance.

These findings were published in the journal of Ceramics International and Journal of the European Ceramic Society. The team was led by Prof. Huang Zhulin at the Institute of Solid State Physics, the Hefei Institutes of Physical Science of the Chinese Academy of Sciences,

Ultrahigh temperature ceramics (UHTCs) are essential materials for thermal protection systems with high melting points and excellent stability. Tungsten-based UHTCs offer excellent resistance to heat and radiation. However, they have faced several challenges in practical applications, such as difficulty in achieving high density during processing, grain coarsening during sintering, and limited oxidation and ablation resistance.

In this study, the research team used a liquid-phase precursor method to synthesize high-purity WC-xTaC and WB₂ ceramic powders. By introducing tantalum carbide (TaC) as a grain growth inhibitor, they successfully controlled grain size in the WC ceramics, achieving a high densification of 97.8% and a hardness of 24 GPa, even without using any binder.

For the WB₂-based composite, the team added silicon carbide (SiC) to improve sintering, resulting in a WB₂–SiC (WS20) material with a densification of 98.2% and an even higher hardness of 26.9 GPa. To further enhance ablation resistance, they incorporated lanthanum oxide (La₂O₃) into the composite.

The final material, WS20L5, demonstrated impressive resistance when exposed to a 2273 K plasma flame, with a mass ablation rate of only 0.463 mg/s and a linear ablation rate of 0.311 μm/s, comparable to conventional zirconium- and hafnium-based UHTCs.

Further analysis revealed that La₂O₃ reacts with SiO₂ at high temperatures to form La₂Si₂O₇, which helps trap boron oxide (B₂O₃) and prevents it from evaporating. At the same time, a protective B-Si-O-La glassy layer forms on the surface during ablation, sealing pores and blocking oxygen from entering the material—effectively improving durability under harsh conditions.

This study provides innovative strategies for optimizing the performance of tungsten-based UHTCs through doping and composite design, according to the team.