Hydrogen content influence on tribological properties of nc-WC/a-C:H coatings

Tribological behavior of hydrogenated W-C/a-C:H coatings deposited by three different sputtering techniques

“…The incorporation of hydrogen into carbon coating significantly modifies friction behavior [1,[19][20][21][22]. Strong dependence of CoF in dry friction on hydrogen content and humidity was reported for both DLC and W-C:H coatings [18][19][20][21][22]. In humid air, CoF of around 0.25 was reported for hydrogen-free DLC but less than 0.1 for the hydrogenated coatings.…”

“…The presence of oxygen or water had a positive effect on friction in hydrogen-free DLC coatings and detrimental effect on hydrogenated coatings due to the chemical reactions of oxygen or water molecules with dangling carbon bonds [22]. In dual magnetron sputtering deposited nanocomposite hydrogenated W-C:H coatings, the degree of hydrogenations was confirmed to be crucial for low CoFs and values below 0.1 can be obtained at sufficiently high hydrocarbon flows even at relatively high humidity (20%-27%) [18]. It was also found out that hydrogen incorporation into the carbon matrix caused reduction of the residual stresses and improved adhesion [18,23].…”

“…The effect of hydrogen originating from added hydrocarbons can be described in terms of saturation of amorphous carbon matrix and closing of the dangling carbon bonds by hydrogen atoms [15,16]. High levels of hydrogenation result in residual stress reduction, significant decrease in the coefficient of friction (CoF) and increase the effectiveness of self-lubrication [17,18]. The carbon deposition rate is strongly correlated with the flow of hydrogen added into…”

Microstructure and Mechanical Properties of Annealed Wc/C Coatings Deposited With Different Gas Mixtures in an RFMS Process

“…On the other hand, it has a low friction coefficient. The WC coating can be deposited on the substrate material by magnetron sputtering, including a direct current magnetron sputtering (DC MS) technique [3][4][5][6][7][8][9][10][11][12][13] and a radio frequency magnetron sputtering (RF MS) technique [14][15][16][17][18][19][20][21][22][23][24]. Moreover, WC coatings can be deposited with a low-pressure and low-temperature plasma system, where tungsten carbonyl is used as a precursor [25][26][27][28][29] and it enables the temperature to decrease near to 300 °C [19].…”

“…Besides the technological parameters, the temperature of the sample surface, the target-to-substrate distance (the distance of the target to the coated surface) and the magnetron power were variable. In order to influence the properties of the WC/C coatings, H 2 [20] and methane (CH 4 ) [14][15][16]19] are the representatives of the gases, which are commonly used in the deposition process. The change in CH 4 flow was also involved in the investigation process because of its effect on the mechanical WC/C coating properties.…”