Dependence of the microstructure and properties of TiC/Ti3SiC2 composites on extra C addition

TiC/Ti3SiC2 composites were synthesized with Ti/Si/C and Al (in which extra C addition ranges from 0 to 25 wt.%) as starting powders by hot-pressed sintering method at 1400 °C under 30 MPa. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to evaluate the phase composition and the fracture surface. The results reveal that with the increase of extra C addition, the content of Ti3SiC2 phase decreases while the content of TiC phase increases. Graphite phase is detected in the samples with extra C addition of 20 wt.% and 25 wt.%. The bending strength decreases from 554.81 MPa to 57.44 MPa due to the decrease of the densification and Ti3SiC2 phase content. The electrical conductivity falls from 42,474.52 s/cm to 1524.95 s/cm, resulting from lower Ti3SiC2 phase content and higher contact resistance.