Microstructure and Mechanical Properties of Spark Plasma Sintered TaC0.7 Ceramics

The TaC0.7 composition was spark plasma sintered (SPS) at 1600°–1900°C using TaC and Ta as the starting powders. Densification process, phase evolution, microstructure development, and the mechanical properties of the composites were investigated. The results indicated that the TaC0.7 composition could be SPS to >95% of theoretical density in 5 min at 1600°C or above. The phase formation was associated with carbon diffusion from the starting particles TaC to Ta to form Ta2C and Ta6C5 as intermediate phases, and subsequently the equilibrium phases of TaCy and ζ-Ta4C3−x. The presence of lamellar ζ-Ta4C3−x regions enhanced the flexure strength (up to 972 MPa) and fracture toughness (up to 13.8 MPa·m1/2).