Regulation on tribological performance of tungsten-doped DLC coatings by choline chloride-urea and-thiourea deep eutectic solvents

Abstract Solid-liquid composite lubrication system has attracted an increased interest for low friction and wear. Nevertheless, the effect of mechanical and surface properties of the solid materials, especially the mechanical and surface properties governed by doping elements, on the tribological performance solid-liquid composite lubrication system is still not well comprehended. Here, we reported the effect of W content on the mechanical and surface properties of W-DLC coatings as well as the tribological properties of W-DLC coatings under (choline chloride-urea and choline chloride-thiourea) deep eutectic solvents lubrication. Although the wear of W-DLC coatings under dry friction increases with W content, the wear under DESs is slight when coatings show excellent wettability to DESs or a DES-derived tribochemical film is formed. We demonstrate that the tribological behavior of W-DLC and DESs composite lubrication system is related to the mechanical properties of W-DLC coatings together with the contact angle and tribochemical interaction between DESs and W-DLC coatings.