Nanoindentation and TEM investigation of spark plasma sintered TiB2-SiC composite

Abstract

The impact of adding 20 vol% SiC on the properties of TiB2 was studied in this research. The spark plasma sintering (SPS) process was used as the preparation technique at 1850 degrees C, the resulted composite was characterized using X-ray diffraction (XRD), field emission electron probe micro analyzer, transmission electron microscopy (TEM), field emission scanning electron microscopy, energy dispersive X-ray analysis, and nanoindentation. The prepared composite presented a relative density of ~98.5%. XRD and TEM results confirmed the in-situ formation of graphite; no in-situ TiC could be detected in the final microstructure of the composite. Forming a low melting point compound between SiO2 and B2O3 oxides lead to the creation of wet interfaces between the ingredients. In terms of mechanical properties, the composite possessed Vickers hardness of 21.6 +/- 2.2 GPa, flexural strength of 616 +/- 28 MPa, fracture toughness of 5.3 +/- 1.2 MPa m1/2, and elastic modulus of 498 +/- 12 GPa. According to the microstructural images, crack deflection, crack branching, crack arresting, crack bridging, and grain breaking events were found to be the main toughening mechanisms in this ceramic. In addition, the nanoindentation investigation indicated the role of SiC addition in improving the elastic modulus, hardness, and wear resistance of the prepared composite.