Hydrogen quantification of magnetron sputtered hydrogenated amorphous carbon (a-C:H) coatings produced at various bias voltages and their tribological behavior under different humidity levels

► Multi-layered PVD-coatings with a-C:H-top layer produced at different bias voltages. ► Analysis of H-content of a-C:H-coatings as a function of bias voltage. ► Influence of H-content on tribological behavior under different humid conditions. ► Lowest friction coefficient μ of 0.015 was measured at 10% relative humidity. ► The wear rate is up to 25 times higher under wet conditions (100.74 ∗ 102 μm3/Nm).