Microstructure, chemical reaction and mechanical properties of TiC/Si₃N₄ and TiN-coated TiC/Si₃N₄ composites

Silicon nitride containing various compositions of as-received TiC and TiN-coated TiC, were hot pressed at 1800°C for 1 h in a nitrogen atmosphere. In TiN-coated TiC/Si₃N₄ composites, TiC reacted first with the TiN coating to form a titanium carbonitride interlayer at 1450°C, which essentially reduced further reactions between TiC and Si₃N₄ and enhanced densification. TiN-coated TiC/Si₃N₄ composites exhibited better densification, hardness, flexural strength and fracture toughness than those of as-received TiC/Si₃N₄. The toughening mechanisms for as-received TiC/Si₃N₄ and TiN-coated TiC/Si₃N₄ composite were attributed to crack deflection, load transfer and crack impedence by the compressive thermal residual stress.