Comparative study of titanium carbide films deposited by plasma-enhanced and conventional magnetron sputtering at various methane flow rates

Titanium carbide (TiCx) films were deposited by reactively sputtering Ti target with varied methane (CH4) flow rates using an unbalanced magnetron sputtering equipment operating in conventional (CMS) and plasma-enhanced (PEMS) mode. The microstructure and properties of the TiCx films were mainly scrutinized with X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, nano indentation, and ball-on-disk tribo-test. As the CH4 flow rate is increased from 4 to 16 sccm, x in the TiCx films deposited by PEMS and CMS is gradually increased from 0.28 to 0.96 and 0.28 to 0.73, respectively; and the concentration of TiC phase in the films rises. A densified microstructure with strong preferred growth is observed in the PEMS-deposited films, while a loose columnar microstructure with almost random growth exists in the CMS-deposited films. When the CH4 flow rate is increased, the hardness of the films deposited by PEMS is firstly increased and then decreased, and reaches a maximum value of 29.6 GPa; but that of CMS-TiCx film is fluctuated below 10.6 GPa. The friction coefficient of TiCx-coated samples against pure aluminum is gradually increased with increasing CH4 flow rate from 4 to 14 sccm, accompanied by a reduction of the aluminum adhesion. The wear rate of the TiCx-coated samples as a function of the CH4 flow rate is firstly decreased and then increased. The lowest wear rate of the PEMS-prepared samples is 7.2 x 10(-16) m(3)/(N.m) obtained at a CH4 flow rate of 14 sccm, while that of the CMS-prepared samples is 9.3 x 10(-15) m(3)/(N.m) obtained at 12 sccm. Therefore, PEMS is a promising method to prepare TiCx films with a good combination of the mechanical properties and wear-resistance against pure aluminum.