Depositions of Titanium Carbide (TiC) are performed on the $Si_3N_4$-TiC composite by chemical vapor-deposition using a $TiCl_4$, $CH_4$, and $H_2$ gas mixture. In this investigation, the effects of deposition temperature, total flow rate of reactant gases, $TiCl_4$ partial pressure, and $CH_4$ partial pressure on the deposition rate are studied. Also, the surface morphologies, Vickers microhardness, and the preferred orientation of TiC deposite are studied.
This experimental results indicate that the chemical vapor deposition of TiC is a thermally activated process. It is obtained that the apparent activation energy is about 31.5 Kcal/mole below the deposition temperature of 1090$^\circ{C}$ and about 10.9 Kcal/mole at temperature above 1090$^\circ{C}$. The deposition rate increases with the increasing of total flow rate from 800 cc/min to 1700 cc/min. However, the deposition rate is constant with the variation of the flow rate from 1700 cc/min to 2000 cc/min. This results shows that the deposition reaction of TiC is controlled by the mass transport mechanism when the deposition temperature is higher than 1090$^\circ{C}$ and the total flow rate of reactant gases is less than 1700 cc/min. On the other hand, the reaction is controlled by the surface reaction mechanism when deposition temperature is lower than 1090$^\circ{C}$ and the total flow rate is larger than 1700 cc/min.
The deposition rate of TiC is increased with the increasing of $TiCl_4$ and $CH_4$ partial pressure. Deposition rate is maximum at the $m^c$ value (mole ratio of C to Ti in the input) of above 1.0. Random orientation is observed and microhardness is increased when $CH_4$ partial pressure increases. However, strong preferred orientation of (200) plane is obtained and microhardness is reduced, when $TiCl_4$ partial pressure increases.
