Dependence of mechanical and tribological properties of $\alpha$-C : H : SiO$_{x}$ films on the bias voltage amplitude of the substrate

The paper presents the AISI 316L stainless steel surface modification by plasma-assisted chemical vapor deposition of $\alpha$-C : H : SiO$_{x}$ film using the pulsed bipolar substrate bias voltage. The mechanical and tribological properties of the $\alpha$-C : H : SiO$_{x}$ film and the steel surface are examined using the nanoindentation method and the pin-on-disk tribometer, respectively. The optimum value is obtained for the amplitude of the negative pulse of the bipolar bias voltage, when the hardness of the a-C:H:SiOx film is high (19 $\pm$ 2 GPa). This hardness value is 3.5 times greater, than the hardness of the AISI 316L steel surface (5.5 $\pm$ 0.1 GPa). At the same time, the coefficient of friction of the film is low (0.08), which is 9 times lower than that of the steel (0.72). The wear rate values are found to be 8.5 $\times$ 10$^{-7}$ and 3.7 $\times$ 10$^{-5}$ mm$^3$ N$^{-1}$m$^{-1}$ for the coated and uncoated steel, respectively. The structure and composition of the obtained films are studied by Raman spectroscopy and scanning electron microscopy.