Improving Tribological Properties of Water-Lubricated Materials Using Sandfish-Inspired Microstructures

Water-lubricated materials are fundamental components of water-lubricated bearings (WLBs), and their friction and wear properties directly impact the performance and durability of WLBs. In this paper, the friction and antiwear properties of two types of water-lubricated materials (nitrile butadiene rubber and ultrahigh molecular weight polyethylene) were improved by mimicking the topographical microgrooves and laminated cross-section of sandfish scales. Ring-block frictional tests demonstrate a lower friction coefficient and reduced wear on bionic-structured water-lubricated blocks compared to pristine samples. Notably, the wear rate shows a maximum reduction of nearly 30%. The effects of microgroove intervals and laminated cross-sections on the tribological performance of water-lubricated blocks were thoroughly analyzed. Finally, the friction and wear of structured and pristine samples were compared under various test conditions including different normal loads, sliding speeds, and pure/contaminated lubricating water. The results indicate that the microstructured samples exhibit superior tribological performance compared to the pristine reference. It is also interesting to note that sandfish-inspired water-lubricated blocks feature robust environmental adaptability with rotary speed and contaminated water. This work provides an effective approach for improving the tribological performance of water-lubricated materials, which will be of great significance for prolonging the service life of WLBs under harsh working conditions.