Spark Plasma Sintering of Ultra-High Temperature Tantalum/Hafnium Carbides Composite


1 School of Metallurgy and Materials Engineering, Iran University of Science and Technology (IUST)

2 Materials and Metallurgical Engineering, Iran University of Science and Technology (IUST)

3 School of Metallurgy and Material Engineering, Iran University of Science and Technology (IUST)


TaC and HfC are thought to have the highest melting point (~4000°C) among all refractory materials. The binary solid solution of TaC and HfC (Ta4HfC5) is also considered as the most refractory material with the melting point 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 (SPS) with addition of MoSi2 as sintering aid and carbon nanotubes (CNTs) 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 reach from 94 % TD (for binder less sample) to near 99 % for samples containing additives, respectively. The average Vickers hardness and fracture toughness values were in the range of 16-19 MPa and 2.9-5.3 MPa.m1/2. 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 surfaces in addition to the Raman spectroscopy analysis.