THE MECHANISM OF COMBUSTION SYNTHESIS OF TITANIUM CARBONITRIDE

Titanium carbonitride, TiC0.5N0.5, is synthesized directly by a self-p ropagating reaction between titanium and carbon in a nitrogen atmosphe re. 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 ex perimental characterizations of quenched samples support a proposed me chanism in which the formation of the carbonitride is a two-step proce ss. The first step involves the formation of the nonstoichiometric car bide, TiC0.5, and is followed by the formation of the product by the i ncorporation of nitrogen in the defect-structure carbide to form the c arbonitride solid solution.