Effect of SiC and TiC Reinforcements on the Mechanical Properties of ZrB2- SiC- TiC Hybrid Composite Fabricated Through Spark Plasma Sintering

This study demonstrates the influence of SiC (20 wt%, 25 wt%, 30 wt%) and TiC (5 wt%, 10 wt%, 15 wt%) reinforcement on the microstructure, mechanical properties and densification behaviour of spark plasma sintered ZrB2 hybrid composite. Results reveal that with the increase in the SiC and TiC addition, the lattice parameters of the generated (Zr, Ti)C and (Zr, Ti)B2 secondary phases were found to be decreased. In addition to this, the residual tensile stresses in the matrix decreased from 253.12 MPa to 239.10 MPa with the addition of SiC from 20 wt% to 30 wt% in the Zr20S5Ti, Zr25S5Ti and Zr30S5Ti composite. The microhardness, relative density and compression strength were enhanced from 19.86 GPa to 23.68 GPa, 95.3% to 96.9% and 412 MPa to 419 MPa with the incorporation of SiC reinforcements from 20 wt% to 30 wt% in ZrB2- 5wt% TiC hybrid composites. The fracture toughness was found to be decreased by 32.03% for the Zr30Si5Ti composite than the Zr20Si5Ti composite due to the coarse SiC grain size and higher intensity of SiC interconnectivity in the synthesized composites. The mechanical properties of the synthesized composites were further improved with the TiC incorporation from 5 wt % to 15 wt% in the ZrB2-25 wt% SiC hybrid composites. The maximum microhardness, compression strength and densification were achieved for the ZrB2- 25 SiC- 10 TiC composite. However, the highest fracture toughness of 9.36 ± 0.53 MPa.m0.5 was obtained for ZrB2- 25 wt%SiC- 15wt% TiC composite due to the presence of higher residual compressive stresses and toughening mechanisms such as particle pull-out, crack deflection and crack bridging.