Experimental Study On Lubricating Mechanism And Tribological Troperties Of Multifunctional Composite Surface Of Hydraulic Components

Hydraulic component is an important part of advanced manufacturing automation equipment.The tribological performance of the mating clearance and surfaces has a significant impact on its performance stability,reliability and service life.As the development of hydraulic system towards the target of lightweight,high speed and high pressure,how to improve the lubrication performance of the clearance surface of hydraulic components and the tribological characteristics of friction and wear resistance has become a technical problem,which need to be solved urgently in the hydraulic field.In this paper,a new concept of multifunctional composite surface technology is proposed.It combines surface coating with surface texture.By manufacturing surface structure on interstitial it can effectively increase the specific surface area of solid surface,which helps surface coating toattached to solid surface.At the same time,surface texture can change the contact state of the solid-liquid interface of the clearance surface and improve lubrication performance.The multifunctional composite surface is prepared on the substrate.And its microstructure,mechanical properties,lubrication effect and friction properties are intensively studied.What's more,the lubrication performance? friction reduction and anti-wear mechanism of the coupling of surface texture and surface coating are also analyzed and discussed.1.The idea of combining surface texture and hard surface coating is proposed and designed.The processing technology is determined according to the material characteristics.On the basis of analyzing the processing characteristics of surface texture technology and surface coating technology,taking the designed texture scale and the characteristics of the required coating into account,the processing sequence of "first surfacetexture and then surface coating" is determined.According to the material characteristics of the substrate,by comparing the advantages and disadvantages of machining technique and laser technique the manufacturing method of surface texture is determined.The surface coating materials and corresponding processing parameters of the two substrates are determined.2.The wetting model of multi-functional composite surface under the influence of geometrical parameters of texture is established.And the adhesion bonding strength of coating/substrate system is analyzed.The contact Angle mathematical model of surface texture is established and the influence of texture geometry on surface wettability is analyzed;the contact Angle of composite surface with four different texture morphologies is measured.The contact Angle calculation model is obtained.The coating/substrate interface types and bonding strength test method are studied.The scratch test method is adapted to directly exam binding force of the two kinds of coating/substrate system.By analyzing the chemical composition of the failure interface the critical point of coating failure is confirmed.And then adhesion force and coating thickness are obtained.3.Comparative study of texture morphology optimization based on texture arrangements based on multi--texture surface CFD simulation model.The loadcarrying capacity of lubrication film of four different surface textures is numerically calculated.Elliptic surface texture is proved to have the most excellent load-carrying capacity.The CFD computational model of multi-texture is established.The lubrication characteristics of clearance surface under rotating motion condition are obtained.The load-carrying capacity of three different texture arrangements of elliptic surface texturehe are studied.The inner pressure cloud diagram and flow field flow diagram of the texture are used to study how texture arrangement,rotation speed and lubricant viscosity affects lubrication performance of each single texture.Synergistic lubrication effect among textures is also analyzed.4.The influence of multi-functional composite surface technology on the performance of friction reducing and wear resistance is studied.The effcts of operating condition parameters and texture arrangement on the lubrication performance of clearance surface are studied through the disc-on-disc mode test.The influence of texture geometric parameters(diameter and depth)on the lubrication statement and tribological properties of the clearance surface are analyzed through the pin-on-disc mode experiment.Through pin-on-disc mode test it is further proved that the existence of surface texture can obviously improve the surface lubrication performance and avoid the occurrence of dry friction.Meanwhile,it is also verified that the surface coating can enhance the wear resistance of clearance surface.