On the effect of the substrate to target position on the properties of titanium carbide/carbon coatings

Titanium carbide/carbon coatings were deposited by hybrid PVD-PECVD process of titanium sputtering in an atmosphere containing acetylene. Samples were placed above the titanium target centre and above the target racetrack in the same vertical distance to the target to examine the effect of the relative substrate to target position on the properties of the deposited coatings. The different positions of the samples led to significantly different levels of the energy influx onto the growing coating. These differing conditions at the substrate led to altering of the coating's chemical as well as phase composition. Also, the grain size, lattice parameter and the mean grain separation were affected by the energy flux change. Coatings deposited above the racetrack with carbon content ≲ 60% exhibited smaller grains, higher amount of the a-C phase and higher mean grain separation. This microstructure refinement yielded 20-30% higher hardness of the coatings deposited above the target racetrack than corresponding coatings deposited above the target centre. Thus, the sample positioning in the chamber proved to be an important parameter for resulting properties of the deposited coatings.