Work

Fabrication and Oxidation Resistance of Metallic Ta-Reinforced High-Entropy (Ti,Zr,Hf,Nb,Ta)B2 Ceramics

Year: 2025

Type: article

Abstract: : High-entropy boride ceramics have significant potential in aerospace applications due to their high melting point, ultra-high hardness, and tunable properties. However, their sintering difficulties and low fracture toughness may limit their widespread use. In this study, Ta metal was incorporated into the high-entropy (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)B2 (HEB) ceramic, and HEB-Ta composite ceramics were fabricated via spark plasma sintering. The impact of Ta content on the densification behavior, mechanical properties, and oxidation resistance of the composite ceramics was investigated. The results show that as Ta content increases, the open porosity of the composite ceramics first decreases and then increases. At 10vol% Ta content, the open porosity reaches its lowest value, 0.15%, and the grain size is 2.33±0.14 μm. As Ta content increases, the composite ceramics’ hardness first increases and then decreases, and the fracture toughness follows a similar trend. At 15vol% Ta content, the hardness and fracture toughness values are at their highest, measuring 20.79±0.17 GPa and 4.31±0.12 MPa·m1/2, respectively. Within 800–1400 °C, the oxidation mass gain and the oxidation depth of the composite ceramics increase progressively with oxidation temperature. At a Ta addition of 10 vol%, the Ta-containing composite ceramics exhibit the best high-temperature stability and oxidation resistance. This behavior stems from an appropriate amount of Ta oxidizing to Ta2O5, which dissolves into the B2O5 glassy phase and increases its viscosity, thereby improving the scale’s high-temperature stability and reducing the oxygen diffusion rate. These results indicate that Ta incorporation enhances the high-temperature stability and oxidation resistance of the composite ceramics.

Source: Materials

DOI: 10.3390/ma18194642