Sintering behavior and mechanical properties of Ta4HfC5-based composites with ZrB2 additive

Ta4HfC5 powder was synthesized using TaCl5, HfCl4 and phenolic resin as raw materials. Then, Ta4HfC5–10 vol% MoSi2 ceramics and Ta4HfC5–10 vol% MoSi2 with different proportions of ZrB2 (10 – 30 vol%) ceramics were sintered by spark plasma sintering. Zr atoms substituted Ta and Hf atoms in Ta4HfC5 during the sintering process at 2000 °C. The sintering behavior and microstructure evolution upon the ceramics are discussed. The mechanical properties of the composites were improved compared to the pure Ta4HfC5 ceramics. The hardness of Ta4HfC5–MoSi2 with 30 vol% ZrB2 increased from around 10 GPa to almost 13 GPa, the flexural strength increased from around 245–435 MPa, and the fracture toughness increased from 2.56 ± 0.12 MPa⋅m1/2 to 4.46 ± 0.20 MPa⋅m1/2.