Direct formation of titanium carbonitrides by SHS in nitrogen

Abstract

An experimental investigation of direct formation titanium carbonitrides by self-propagating high-temperature synthesis (SHS) was conducted using compacted samples of titanium and carbon powders ignited in gaseous nitrogen. Effects of sample green density, nitrogen pressure, and diluent content on the degree of conversion and flame-front velocity were studied. For the undiluted samples, a low degree of nitrogen uptake was obtained, primarily due to the excessive melting of titanium during the reaction. Results indicated that the addition of diluent TiN was required in order to achieve the complete conversion. Three stoichiometric carbonitrides with the compositions of TiC 0.7N 0.3, TiC 0.5N 0.5, and TiC 0.3N 0.7 were synthesized in this study. The required diluent content and nitrogen pressure were found to increase with the increase of nitrogen content in the final product. For the TiC 0.7N 0.3, complete conversion was achieved by using a sample made up of 0.9Ti + 0.7C + 0.1TiN under nitrogen pressures of 0.62 MPa and above. More diluents and higher nitrogen pressure were necessary in the synthesis of TiC 0.5N 0.5 and TiC 0.3N 0.7, which were synthesized from the 0.75Ti + 0.5C + 0.25TiN sample at 1.14 MPa of nitrogen and the 0.6Ti + 0.3C + 0.4TiN sample at 1.65 MPa of nitrogen, respectively.