Wear and Corrosion Resistance of a-C:H:SiO_x Coating on Medical 316L Stainless Steel

The paper studies the adhesion, mechanical, tribological, anti-corrosion properties and the surface morphology of a-C:H:SiO_x coatings after their plasma-assisted chemical vapor deposition onto the grade AISI 316L stainless steel substrate applying a mid-frequency bias voltage to the substrate. The coating structure, chemical composition and surface morphology are studied using the Raman and energy-dispersive x-ray spectroscopies, atomic force and scanning electron microscopies. The tribological properties of the AISI 316L stainless steel are examined using the ball-on-disk method against the WC-Co and 100Cr6 balls under a 3-10 N load. The 400 m run test shows the low friction coefficient (0.07-0.16) and the low wear rate (5·10⁻⁷-8.3·10⁻⁷ mm³/N m) of the a-C:H:SiO_x-coated steel sample against both ceramic and metallic counterbodies under the same loads. It is found that the wear rate of the coating is two orders of magnitude lower than that of the steel substrate. Deposition of the a-C:H:SiO_x coating on the steel surface reduces the corrosion rate from 11.3·10⁻⁴ to 61.7·10⁻⁶ mm/year. Moreover, the a-C:H:SiO_x coating deposition changes the positive surface potential to negative.