EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

A recent study suggests about 20 % of the consumed energy worldwide is related to friction and 18 % of this energy can be saved. Carbon alloyed transition metal dichalcogenide coatings present a tremendous potential in domains where friction reduction is aimed. They possess exquisitely low friction coefficients in diverse environments and can self-adapt to a variety of sliding conditions. In this investigation, a DC magnetron sputtering device is utilized to deposit MoSeC coatings with carbon content from 6 to 60 at.%C. Then, with compositional, morphological, structural, mechanical and tribological characterization techniques, the influence of carbon content on the final MoSeC film performance is analyzed. A decrease in the chalcogenide over transition metal (Se/Mo) ratio with an increasing carbon content of the films was observed. SEM (scanning electron microscopy) allowed to detect a columnar cross-sectional growth with high porosity and roughness for the pure MoSe₂ films but less voids and continuously more compact development for medium and high carbon content coatings. The scratch test has shown the occurrence of the best adhesion strength for the 51 and 60 at. % C films. The stiffness and hardness of the coatings increase almost proportionally to the carbon content of the films, except for the two highest carbon content films, in which these properties almost stagnate. From POD (pin-on-disk) experiments performed in humid air, NBR (nitrile rubber) countersurfaces sliding against MoSeC demonstrate higher friction values than the steel countersurfaces rubbed on the coating, and that the CoF (coefficient of friction) is higher at 25°C than at 200°C. The lowest absolute specific wear rates were achieved for the 51 % of at. C, which combines increased hardness, stiffness and compactness. The study shows the potential of TMD-based coatings for friction and wear reduction sliding against rubber.