High-strength TiB₂-TaC ceramic composites prepared using reactive spark plasma consolidation

This study demonstrates that reactive consolidation achieved via spark plasma sintering (SPS) is an effective strategy to enhance the high-temperature flexural strength of TiB₂-based ceramics. Monolithic ceramics of TaC and TiB₂ were consolidated by non-reactive SPS and were used as reference samples. The microstructural development during room- and high-temperature strength tests was analyzed. The room-temperature strength of TiB₂ ceramics was analyzed as a function of the grain size. The high-temperature strength and associated microstructural development of monolithic TaC ceramics are reported for the first time. The TiB₂-TaC ceramic system was then consolidated by reactive SPS at 2000 °C. The flexural strength of the 10 wt% TaC-TiB₂ ceramic composites reached 533 MPa at room temperature and 480 MPa at 1600 °C. The development of the (Ti,Ta)(C,B) phase was considered the main reason for the preservation of the high strength up to 1600 °C. Both bulk TaC and TiB₂ exhibited drastic decreases in their bending strengths at 1600 °C because of the activation of plastic deformation associated with high-temperature creep, and their strength did not exceed 210 MPa.