THE MECHANISM OF COMBUSTION SYNTHESIS OF TITANIUM CARBONITRIDE

Titanium carbonitride, TiC0.5N0.5, is synthesized directly by a self-propagating reaction between titanium and carbon in a nitrogen atmosphere. Complete conversion to the carbonitride phase is achieved with the addition of TiN as diluent and with a nitrogen pressure greater than or equal to 0.6 MPa. Thermodynamic phase-stability calculations and experimental characterizations of quenched samples support a proposed mechanism in which the formation of the carbonitride is a two-step process. The first step involves the formation of the nonstoichiometric carbide, TiC0.5, and is followed by the formation of the product by the incorporation of nitrogen in the defect-structure carbide to form the carbonitride solid solution.