Influence of the PACVD process parameters on the properties of titanium carbide thin films

Wear-resistant titanium carbide (TiC) coatings were deposited by plasma-assisted chemical vapour deposition on high-speed steel. The influence of the partial pressure ratio of methane and titanium tetrachloride (p(CH4)/p(TiCl4)), the plasma voltage and the pulse/pause ratio on the composition and properties of the TIC coatings have been investigated. Small partial pressure ratios p(CH4)/p(TiCl4) up to about 15 result in nearly stoichiometric TiC coatings at high plasma voltage. Higher partial pressure ratios cause excess carbon, which is bound as C-C or C-H. An increasing carbon content was found also for both increasing plasma voltage and increasing pulse/pause ratio. The layer hardness was found to decrease with increasing excess carbon. No significant influence of composition on the friction coefficient has been detected. (C) 1998 Elsevier Science S.A.