Self-lubricating behavior of VN coating catalyzed by solute Ag atom under dry friction and oil lubrication

Abstract

The development of hard-yet-tough ceramic coatings with self-lubricating behavior is an urgent technological requirement to reduce mechanical friction losses and energy consumption. However, traditional ceramics possessing the limited self-lubricating ability and poor toughness have limited their practical applications. To tackle the above-mentioned problems, we modified ceramic material vanadium nitride (VN) to prepare the catalytically active V-Ag-N solid solution coating by magnetron sputtering and realized high hardness, high toughness, and excellent self-lubricating performance under dry friction and oil lubrication conditions. Through detailed experimental investigations, we explain the enhanced mechanism of both hardness and toughness because of solute Ag; moreover, the solute Ag can trigger the appearance of lubricating silver vanadate phase in dry friction and result in a low coefficient of friction. Besides, it was confirmed that the solute Ag atom would induce effectively catalytic ability for in situ formation of self-lubricating onion-like-carbon structures (OLCs) scrolls from base oil at the sliding interface. The novel strategy would be to open a window for more efficiently catalyzing the in situ formation of silver vanadate and OLCs scrolls activated by solute Ag atoms and more significantly improving the hardness and toughness, thereby further improving self-lubricating behavior under dry friction and oil lubrication conditions.