Influence of non-smooth surface on tribological characteristics of CFRPEEK flow distribution pair of high-pressure piston pump under seawater lubrication

Abstract Non-smooth surface technology has been effectively used to improve tribological characteristics. For better tribological performance of the flow distribution pair, many researchers have focused on the influence of the existence of pits on non-smooth surfaces. However, such research route may ignore the specially combined effects of other tribological conditions, such as non-metal materials with different pits types on its non-smooth surface under seawater lubrication. The innovation of this paper is that, unlike most studies that often use pure water or lubricating oil as the working medium and use simple geometric workpieces as the object of friction and wear experiments, this study uses natural seawater and uses a 1: 1 ratio model of non-smooth surface flow distribution pair. Also, the use of carbon fiber-reinforced polyether ether ketone (CFRPEEK) as the lower sample material is uncommon in this research area, providing novel insights into its tribological performance under seawater lubrication. By analyzing the results of CFD simulation and the results of friction and wear experiments, the dominant wear mechanism between CFRPEEK and 431 stainless steel is abrasive wear. And non-smooth surface is superior to smooth surface in terms of lower friction coefficient, over 50% reduction in wear loss, and reduced surface roughness. Among the tested pit types, hemispherical pits exhibit the lowest friction coefficient. Furthermore, these results can be explained by the anti-wear mechanism: Changing the shape of the water film to improve the water film load-carrying capacity, the pits not only store the lubricant to improve the lubrication state on the friction interface, but also collect the abrasive dust to reduce the phenomenon of abrasive wear. Therefore, utilizing numerical simulations combined with friction and wear experiments to explore the anti-wear mechanisms and choosing the appropriate type of pit on non-smooth surface for friction and wear tests will provide inspirational ideas for future research.