Strengthening of TiC ceramics sintered by spark plasma via nano-graphite addition

Abstract

In this research, 5 wt% nano-graphite was added to titanium carbide and its impacts on the microstructure and mechanical qualifications were evaluated. Monolithic and graphite-doped TiC samples were manufactured at 1900 °C under 40 MPa for 10 min by spark plasma sintering method. Graphite nano-flakes enhanced the densification behavior, flexural strength, and friction coefficient of TiC ceramics. The XRD, microstructural, and thermodynamical assessments revealed the occurrence of a chemical reaction between the carbonaceous phase and TiC oxide layers, namely TiO2, and the formation of non-stochiometric TiCx and in-situ TiC. Although introducing nano-graphite as an additive decreased the Vickers hardness of TiC by ~34% (2071 HV0.1 Kg for the doped specimen), it had a positive influence on the flexural strength (504 and 633 MPa for monolithic and graphite doped samples; respectively). Finally, an average friction coefficient of 0.35 was obtained for TiC-5 wt% graphite ceramic, ~13% higher than that of the monolithic TiC sample.