Research On Tribological Properties Of Textured Cylinder Liner Surface Encapsulated With Composite Solid Lubricant

According to statistics,the energy loss caused by friction is about 4.5%of the gross national product.About 70%of Marine machinery failure is concerned with its internal friction and wear.The relevant data show that piston,cylinder liner and valve are the most common components in the Marine main engine system failure,and the piston ring and cylinder liner friction pair in the main engine are in high temperature,high pressure and strong vibration operation for a long time,and the most likely to occur friction and wear.Therefore,reducing excessive friction and wear between cylinder liner and piston ring friction pair is of great significance to improve the economy and reliability of diesel engine.Combined with finite element simulation and friction and wear test,this paper carried out a study on the surface tribological properties of textured cylinder liner encapsulated with composite solid lubrication materials.The main research contents and achievements are as follows:Firstly,finite element simulation was carried out around the micro-texture with different diameter parameters on the cylinder liner sample surface.The transient dynamics module in Ansys workbench software was used to explore the stress variation rule in the micro-texture region during the reciprocating motion of the cylinder liner-piston ring friction pair,and the influence of the texture diameter on the stress distribution around the micro-texture was analyzed.The simulation results show that stress concentration occurs in the micro-texture region of the cylinder liner samples with four different texture diameters,and the stress concentration is mainly at the edge of the micro-texture.However,with the increase of the texture diameter,the variation range of stress on the cylinder liner sample surface decreases correspondingly,and the equivalent stress peak also decreases with the increase of the texture diameter.Secondly,circular textures with different diameters were processed in the middle position of the sample surface of the cylinder liner by laser etching technology,and the PI/WS₂composite lubrication material after ball milling was filled into the micro-texture by hot pressing method to construct the composite lubrication structure.A reciprocating friction and wear testing machine was used to investigate the effects of the proportion of lubricating materials,texture diameter parameters and different load conditions on the tribological properties of cylinder liner samples with composite lubrication structure.The test results show that the cylinder liner samples with a micro-texture diameter of 0.8mm and a mass ratio of WS₂to polyimide of 3:1 have the best anti-friction and wear-resisting properties at normal temperature and 20MPa.Compared with the blank sample,the friction coefficient of the cylinder liner sample filled with bi-physical solid lubrication material in the micro-texture is reduced by 12.9%,and the wear of the paired piston ring is reduced by 47.6%.The cylinder liner samples filled with bi-physical solid lubrication materials can adapt to the working environment of higher load.In the micro-texture,the release range of bi-physical lubrication materials increased with the increase of applied load,the area of solid lubrication film also increased,and the friction coefficient of cylinder liner samples almost did not change with the increase of working load.Finally,SEM,EDS and other detection methods were used to analyze the worn cylinder liner sample surface,and Raman spectroscopy and X-ray photoelectron spectroscopy were used to analyze the solid lubrication film formed on the friction surface,revealing the friction reduction mechanism under the synergic action of multiple elements such as surface micro-texture,polyimide and WS₂.The results are as follows:the bi-physical solid lubrication material in the micro-texture is released to the surface of the cylinder liner and the edge of the micro-pit through the combined action of extrusion and friction heat of the piston ring.WS₂ and polyimide in the micro-pit area are stripped and slipped through cutting,extrusion and spalling.Part of WS₂ and polyimide decompose under the action of high contact stress and frictional shear stress,and react with oxygen in the environment and cylinder liner matrix to form solid lubrication film.The other part of lubrication material is dragged to the sliding direction and expands into a part of the lubrication film.The self-lubricating film experienced the cycle process of formation,damage,shedding and regeneration.These lubricating films change the contact state of the friction pair,effectively protect the friction interface,and can play a role in reducing friction and anti-wear.