Reactive processing of titanium carbide with titanium - Part 2 Solid-state hot pressing

The reactive hot pressing of titanium-titanium carbide mixtures to form substoichiometric titanium carbide was studied as a function of time, temperature, pressure and composition using a Box-Behnken experimental design. Thirty samples were hot pressed at 1200 to 1600° C and 7 to 35 MPa (1000 to 5000 psi) for 0.5 to 1.5 h from mixtures containing 10 to 30vol % titanium metal. Twenty three of these samples had final densities in excess of 95% of the theoretical value. A model for the grain growth during hot pressing was developed by consideration of Kuczynski's semi-empirical sintering model and classical grain-growth models. The modification involves development of a factor which describes the behaviour of the system as a function of composition. Microstructural data, selected area diffraction patterns, and the activation energy for grain growth all indicate that the grain growth is controlled by diffusion through Ti₂C-TiC and/or TiC-TiC boundaries. Densification during hot pressing was interpreted in terms of the creep of titanium metal using a power-law creep model. The activation energy for densification agrees well with the activation energy for the self-diffusion of titanium. The high densities obtained also indicate that the densification depends largely on the ductile nature of the titanium metal.