Titanium carbide/carbon nanocomposite hard coatings, which consist of TiC nanocrystallites embedded in amorphous carbon matrix (nc-TiC/a-C:H coating), were deposited by sputtering of a rotating cylindrical titanium sputtering target in argon/acetylene gas mixture on high speed steel and tungsten carbide substrates which were placed on a DC biasable holder performing complex rotation around the Ti cathode. nc-TiC/a-C:H coatings with varying chemical composition prepared at 10 kW DC power (320 C), 20 kW (450 C) and 30 kW (450 C) and bias of -100 V reached maximal hardness of 24 GPa, 37 GPa and 28 GPa respectively. Because it could be expected that the optimal composition of the coating leading to maximal hardness should be reached independently on the applied power a process study was performed. Ti/Ar line intensity and discharge voltage showed sudden drop at the conditions where the maximal hardness was reached. EDX analyses show also sudden drop in Ti atomic concentration at this moment. The maximal hardness of a coating was reached always at conditions preceding the sudden drop which could be used for setting optimal deposition parameters to produce hard, well adherent and thick enough TiC/C coatings with low internal stress using industrially attractive concept of rotating cylindrical magnetron.