Synthesis of TiC reinforced Ti matrix composites by spark plasma sintering and electric discharge sintering: A comparative assessment of microstructural and mechanical properties

Ti-TiC composite materials were produced by spark plasma sintering (SPS) and electric discharge sintering (EDS) of spherical Ti powders with surface-embedded TiC. Hardness (H-IT) and reduced elastic modulus (E-r) were estimated using the nanoindentation method with an applied load of 100 mN, and compared with the micro-Vickers hardness value. The microstructure of SPS composite compacts revealed that the TiC particles were uniformly distributed only along the Ti particle boundary. On the other hand, for the EDS composite compacts, the strip-like TiC particles of 1-2.5 mu m in size were homogeneously dispersed in the Ti matrix, indicating that the discontinuous and randomly orientated TiC can more efficiently impede the plastic flow of the matrix phase of Ti. The micro-Vickers and nanoindentation hardness for the SPS composite compacts slightly increased with increased TiC content from 0 to 20 wt%, the increments of which were about 67 Hv and 0.7 GPa, respectively. Meanwhile, the EDS composite compacts exhibited significantly higher micro-Vickers and nanoindentation hardness with the increment of 653 Hv and 6.5 GPa, respectively. This result was ascribed to the TiC particles uniformly dispersed across the Ti matrix. Accordingly, the ratio values, such as H-IT/E-r and H-IT(3)/E-r(2), were also significantly higher for the EDS composite compacts at all the range of TiC content due to stiffening and hardening effects derived from the TiC reinforcement. Therefore, the better incorporation of the TiC in the Ti matrix significantly improved the hardness and wear properties of the Ti composite reinforced with TiC produced by EDS compared with the SPS process.