On the reactive spark plasma sinterability of ZrB₂–SiC–TiN composite

In the present research, the influence of TiN addition on the ZrB₂–SiC composite was studied. Hereof, TiN-doped ZrB₂–SiC composite was manufactured via the route of reactive spark plasma sintering under an applied load of 40 MPa at the peak temperature of 1850 °C for 360 s. Mechanical properties, microstructure evaluation, and sinterability were investigated and compared to the non-doped ZrB₂–SiC. X-ray diffraction analysis, thermodynamic appraisal, energy dispersive spectroscopy, and scanning electron microscopy divulged the formation of in-situ h-BN, ZrO₂, and ZrN as well as the (Zr,Ti)B₂ solid solution in TiN-doped ZrB₂–SiC. Comparing the relative density of 95% for the TiN-free sample with the relative density of 94.1% for the sample containing TiN, the addition of TiN increased porosity content owing to the formation of in-situ BN with layered structure. Flexural strength decreased from 460.2 MPa for TiN-free ZrB₂–SiC to 435.9 MPa for TiN-doped ZrB₂–SiC, due to matrix grain growth and relative density drop. In contrast, indentation fracture toughness and Vickers hardness increased to 6.1 MPa.m^1/2 and 29.1 GPa, respectively, as the result of TiN addition.