Study On The Influence Of Surface Modification On The Friction Performance Of Water Lubricated Bearings

Water-lubricated bearings are increasingly used in stern bearings due to their good environmental compatibility and economy.However,because the widely used water-lubricated bearing materials are mostly non-metallic materials,they have poor hydrophilicity,weak thermal conductivity,poor friction properties and poor sediment resistance.These shortcomings have limited the practical application of water-lubricated bearings in multiple waters.Therefore,it is of great significance to modify the surface of water lubricating materials,improve their surface hydrophilicity,increase their friction properties and resistance to sediment,and promote the use of water lubricated bearings in different waters.In order to improve the hydrophilicity of water-lubricated bearings,Thoron SXL,a Sailon material for water-lubricated bearings,is used as the research object,and pit textures with different size parameters are prepared on the surface by laser processing technology.The contact angle is measured using a contact angle meter Using three-dimensional topography instrument and scanning electron microscope to measure and characterize the surface morphology after processing.The three-dimensional parameters in ISO25178 were selected to analyze the relationship between surface morphology and wettability.A geometric model of pit texture was established,and the influence mechanism of morphology changes on the surface contact angle was analyzed based on the transition theory.On the friction tester,the effects of texture parameters on the friction coefficient and wear of the specimen under different working conditions were studied by setting the speed and load.The results show that proper texture design can effectively improve the surface wettability and reduce the contact angle.The larger the texture diameter and depth,the smaller the contact angle of the material surface.In the ISO25178 three-dimensional parameter system,there is a strong correlation between kurtosisS_{k u},skewnessS_{s k},and surface wettability.The smaller the kurtosisS_ku,the larger the skewnessS_sk,and the better the surface wettability.The cosine of the contact angle of the surface is consistent with the change trend of the roughness rate,and the contact angle decreases as the roughness rate increases.The function equation between the texture parameters and the contact angle was established by the transition model,and it was optimized by the fitting method.Appropriate texture design can effectively improve the friction performance of the material.With the increase of texture pitch and laser power,its friction coefficient decreases first and then increases.In order to improve the anti sediment performance of water lubricated bearing,the texture design of rubber material for water lubricated bearing was carried out,and the texture with different sizes was processed on the surface of the sample by laser marking machine.The friction test was carried out on UMT-2 friction tester.The influence of surface texture on the tribological performance of water lubricated bearing under different working conditions was studied by adjusting the load,running speed and the composition of sediment in water.The surface morphology and roughness of the samples before and after friction were measured and characterized by SEM and three-dimensional topography instrument,and the relationship between roughness and friction coefficient was analyzed.A non-contact three-dimensional profilometer（microxam-800）was used to measure the wear of brass samples after friction.EDS and metallographic microscope were used to analyze the elements and wear marks of the upper and lower samples after friction,and ANSYS FLUENT software was used to analyze the lubrication state and the wear mechanism.The results show that there is a positive correlation between the surface roughness and the friction coefficient.The texture of rubber bearing surface has a good retention effect on sediment,and has a great influence on the wear of brass sample.The wear patterns of textured samples under water lubrication are adhesive wear,abrasive wea r and fatigue wear,which are related to the texture parameters and friction conditions.In order to further improve the hydrophilicity of water lubricated bearings,the PVA/PVP/PAA TN hydrogel was grafted onto the surface of the water lubricated bearing rubber material by introducing double bond active groups onto the surface of epoxy resin and introducing the double bond active groups onto the surface of the water lubricated bearing.The friction test was carried out on the UMT-2 friction tester,and its sliding speed and load were set up.The effect of surface grafting hydrogel on the friction properties of rubber materials under different working conditions was studied.The results of the study show that the hydrogel has excellent hydrophilicity and has a pore structure inside.During the wear process in a wet environment,due to the external load,the water stored in the pores is squeezed out to form fluid lubrication.In order to achieve a low friction coefficient under wet conditions,the surface grafted hydrogel can effectively reduce the friction coefficient of the material compared to untreated rubber samples.