Spark plasma sintered tantalum carbide: Effect of pressure and nano-boron carbide addition on microstructure and mechanical properties
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TaC and TaC-1 wt.% B(4)C powders were consolidated using spark plasma sintering (SPS) at 1850 degrees C and varying pressure of 100, 255 and 363 MPa. The effect of pressure on the densification and grain size is evaluated. The role of nano-sized B(4)C as sintering aid and grain growth inhibitor is studied by means of XRD, SEM and high resolution TEM. Fully dense TaC samples were produced at a pressure of 255 MPa and higher at 1850 degrees C. The increasing pressure also resulted in an increase in TaC grain size. Addition of B(4)C leads to an increase in the density of 100 MPa sample from 89% to 97%. B(4)C nano-powder resists grain growth even at high pressure of 363 MPa. The formation of TaB(2)/Carbon at TaC grain boundaries helps in pinning the grain boundary and inhibiting grain growth. The effect of B(4)C addition on hardness and elastic modulus measured by nanoindentation and the indentation fracture toughness has been studied. Relative fracture toughness increased by up to 93% on B(4)C addition. (C) 2010 Elsevier B.V. All rights reserved.