Study On Friction Properties Of Ceramic Materials For Friction Pair Of Mining High Water-based Axial Piston Pump

The mining axial piston pump is the core power source of the high water-based hydraulic system in the mining area,which is very important for efficient mining and safety support of the working face in the mining area.With the increasing demand for high strength,large working resistance,and large mining height of the rated operational characteristics of the hydraulic support in the underground mining area,higher requirements are put forward for the wear resistance of the high water-based axial piston pump.The lubrication and wear resistance of the key friction pairs inside the pump directly affects the whole piston pump’s operation performance and service life.Therefore,this paper starts with the selection of the key friction pair materials in the high-water-based emulsion pump for mining,redesigns the friction pair matching materials,explores the friction and wear characteristics and wear mechanism of different engineering ceramic materials and their different material combinations,and selects the best friction pair materials to improve the lubrication performance of the axial piston pump for mining,to provide guidance for the design of high-water-based medium hydraulic components for mining.The specific research work is as follows:Firstly,taking the plunger pair of mine high water-based axial piston pump as the research object,its motion,force,and application conditions are analyzed.Based on this,various factors affecting the lubrication performance of piston pump and the correlation between them are summarized.On this basis,the specific technical scheme to improve the lubrication performance of the piston pair is given.Then the method of improving the material of the piston friction pair of the piston pump is put forward as the research focus of this paper.Secondly,the tribological properties of several engineering ceramic materials under high water-based lubrication conditions were studied by MFT-5000 friction and wear tester.The variation of friction coefficient,wear rate,wear morphology,and wear mechanism of each material combination under the influence of normal load and sliding velocity were studied.The material combinations studied are zirconia（Zr O₂）,alumina（Al₂O₃）,silicon nitride（Si₃N₄）,and silicon carbide（Si C）,which are paired with 304 steel,respectively.The results show that the friction coefficient and wear rate of the Zr O₂/steel pair is the lowest under the same working conditions.The main wear mechanism of the friction pair is micro-plowing at low speed and light load and gradually transformed into oxidation wear and plastic deformation with the increase of speed and load.Subsequently,the tribological properties of four ceramics paired with Zr O₂ were further studied based on the above research results.The results show that the friction coefficient and wear rate of Al₂O₃/Zr O₂ is the lowest,and the wear mechanism is mainly fatigue wear and abrasive wear.Therefore,if considering the application of ceramic materials in high water-based hydraulic components,Zr O₂ can show the best friction and wear characteristics;when considering the combination of all ceramic friction pair materials,Al₂O₃/Zr O₂ pair can show the best tribological properties.Thirdly,Zr O₂/steel and steel/steel were selected as the friction pair matching materials.The influence of ambient temperature change on the tribological properties of the two friction pairs under high water-based emulsion lubrication was studied experimentally.The results show that the friction coefficient and wear rate of steel/steel friction pair increase greatly with the increase in temperature,and the main wear mechanism is three-body abrasive wear.The friction coefficient of the Zr O₂/steel friction pair decreases with the temperature increase,and the wear rate growth ranges slightly.The wear mechanism is mainly abrasive wear and plastic deformation.Therefore,to a certain extent,ceramic materials can promote the lubricating properties of high water-based hydraulic components under temperature-rising conditions.Finally,the stress and strain of the piston pair of four kinds of engineering ceramics and 304 steel materials are analyzed by finite element analysis.The results show that the equivalent contact stress and the deformation in the principal stress direction of the friction pair of Zr O₂/steel are smaller than those of the other three ceramic materials.When comparing the friction pairs of four ceramics and Zr O₂ materials,it can be found that the equivalent contact stress and the deformation in the principal stress direction of the model are related to the elastic modulus of the ceramic.When ceramic coatings with different thicknesses are added to the piston pair’s surface,the coating thickness change influences the deformation and stress in the principal stress direction of the friction pair.And the coating thickness is 0.5mm,and the contact stress and strain are the smallest,so there is an optimal coating thickness.