In Situ Preparation of Nano-Cu/Microalloyed Gradient Coating with Improved Antifriction Properties

Abstract

In order to solve the failure problem between the crankshaft and the connecting rod friction pair, nano-Cu/microalloyed gradient coating was prepared on the surface of the crankshaft by in situ gaseous nitriding process. Electron probe analysis confirmed the change of delamination after the in situ nitriding process, and the formed coating included three layers: the upper layer is a nano-copper layer, the middle is a microalloyed layer (containing Cu, N, and Fe elements), and the bottom is a nitriding diffusion layer. The change of profile hardness curve was analyzed by microhardness test. The bonding force between the coating and the substrate was analyzed by the scratch test. The friction and wear test showed that the nano-Cu/microalloyed coating could achieve the effect of antifriction. Moreover, self-lubricating and antifriction mechanisms of nano-copper coating were proposed. These results indicated that the in situ gaseous nitriding process could provide a new surface modification technique for the precision friction pairs.