Mechanical Properties, Strengthening and Toughening Mechanisms of Reactive-Hot-Pressed TiB2-SiC-Ni Ceramic Composites

A TiB2-SiC-5 wt %Ni ceramic composite with high flexural strength and fracture toughness was fabricated in the reactive hot pressing (RHP) process. Different sintering times and sintering temperatures were employed. The strengthening and toughening mechanisms were investigated in detail. The composition and microstructure were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM) and energy-dispersive spectroscopy (EDS). The sintering time and sintering temperature had a significant influence on the mechanical properties and microstructure of the composite. The mechanical properties decreased as the sintering time was increased from 30 to 45 min, and subsequently increased with the further increase of the sintering time. The mechanical properties of the composite increased gradually as the sintering temperature increased. For the investigated range of parameters, the composite prepared at 1700 °C for 30 min had the optimum comprehensive mechanical properties with flexural strength of 1121 ± 31 MPa, fracture toughness of 7.9 ± 0.58 MPa⋅m1/2 and hardness of 21.3 ± 0.62 GPa. The improved flexural strength and fracture toughness of the composite were attributed to the strengthening and toughening effects of Ni and the elongated TiB2 grains, the intragranular nano-particle structure, and the dislocations and stacking fault. The clean interface is also conducive to the improved flexural strength.