Effect of C/TiO2 ratio in raw materials on thermal conductivity of titanium carbonitrides synthesized by carbothermal reduction

Abstract

Titanium carbonitride is a major raw material for the production of Ti(C,N)-based cermets, and their properties affect the performance of the cermets as tool materials. Enhancement of the thermal conductivity of the carbonitride is required to improve the thermal shock resistance of cutting and wear-resistant tools. While the thermal conductivities of Ti(C,N) have been previously studied, the reported data have been inconsistent and the intrinsic thermal conductivity of Ti(C,N) has not been obvious. Ti(C,N) powders with different C/TiO2 ratios in raw materials were systematically prepared by the carbothermal reduction process with much attention paid to prevent contamination by metallic elements. Sintered specimens were obtained by hot pressing to lower the sintering temperature, and the thermal conductivities were evaluated. The maximum thermal conductivity obtained in the present study was approximately 35 W m−1K−1. The N2 atmosphere was better than the Ar atmosphere for sintering at 1900 °C to increase the thermal conductivity of Ti(C,N). The present paper discusses the importance of the [C]/([C]+[N]) ratio and nonmetal/metal ratio of the specimens on thermal conductivity. Further optimization of the sintering condition is also expected to enhance the thermal conductivity.