Spark Plasma Sintering of Ultra-high Temperature Tantalum/HafniumCarbides Composite

TaC and HfC are thought to have the highest melting pointamong all refractory materials. The binary solid solution of TaC and HfC is also considered as the most refractory material with melting points over 4000 °C and valuable physical and mechanical properties. The main goal of this work is to fabricate TaC/HfCbased composites which consolidated by means of spark plasma sintering with addition of MoSi2 as sintering aid and carbon nanotubes as reinforcement at 2000 °C. The effects of additives were investigated in terms of densification, mechanical properties, phase and microstructural evolutions. It was demonstrated that the relative density could reachnear 99 % for samples containing additives, from 94 % TD for sample without sintering aid respectively. The average Vickers hardness and fracture toughness values were in the range of 16-19 MPa and 2.9-5.3 MPa.m^1/2. The samples containing CNTs showed improved fracture toughness and the survivability of CNTs, after spark plasma sintering, was proved by scanning electron microscopy of fractured surfacesin addition to the Raman spectroscopy analysis.