The role of onion-like carbon addition on high pressure and high temperature sintered TiN0.3.

The high melting point and the covalent bond between Ti and N made the titanium nitride matrix composites difficult to sinter using conventional sintering methods. TiN 0.3 and onion-like carbon (OLC) were used as starting materials for the preparation of TiN 0.3 /onion-like carbon composites under high pressure and high temperature (HTHP) of 5.0 GPa and 1100–1400 °C for 10 min. The phase formation, microstructure, and mechanical properties of TiN 0.3 composites with different contents of onion-like carbon were systematically investigated by XRD, SEM, and TEM. The experimental results showed that TiC 0.3 N 0.7 was formed by diffusion of TiN 0.3 with onion-like carbon due to the dual effect of high concentration of N vacancies and high pressure, and the onion-like carbon was gradually graphitized with increasing temperature. The composites of TiN 0.3 /5 vol% onion-like carbon sintered at 1200 °C possessed the optimum properties, with hardness of 15.2 GPa and fracture toughness of 3.9 MPa·m1/2. Compared with TiN composites prepared by conventional methods, the non-stoichiometric compound reduced the sintering temperature of the TiN composites. [Display omitted] • The OLC was used as a binding agent component. • The Vickers hardness of the sintered body was enhanced by the diamond. • A new method of forming TiC 0.3 N 0.7 by N vacancies in TiN 0.3 with OLC defects [ABSTRACT FROM AUTHOR]