Abstract
In the present research, near-net-shapein situ TiB2/TiN and TiB2/TiN/Ni composites were fabricated from cold-sintered BN/Ti and BN/Ti/Ni powder blends by pressureless displacement reaction synthesis or thermal explosion under pressure. In both approaches, the processing or preheating temperatures (≤1200 °C) were considerably lower than those typical of current methods used for the processing/consolidation of ceramic matrix composites. Microstructural characterization of the materials obtained was performed using X-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Mechanical properties were evaluated by measuring microhardness, fracture toughness, and three-point bending strength. Application of a moderate external pressure (≤250 MPa) during self-propagating synthesis (SHS) synthesis was shown to be sufficient to ensure full density of the TiB2/TiN/Ni composite. The entire procedure of thermal explosion under pressure could be performed in open air without noticeable oxidation damage to the final product. The high fracture toughness of thein situ synthesized TiB2/TiN/Ni composite (20.5 MPa√m) indicated that the finely dispersed ductile Ni phase was effective in dissipating the energy of cracks propagating in the ceramic matrix.
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