Study On Laser Ablation Micro Texture To Improve The Friction Performance Of Axial Piston

As the core component of the plunger pump,under the condition of high speed and high pressure,the plunger often produces a certain eccentricity during the movement,resulting in the rupture of the oil film between the plunger and the cylinder block,and then it will have direct contact with the cylinder block,resulting in the wear of the plunger surface,which will seriously affect the service life of the plunger pump.Based on the laser ablation micro texture technology,the surface of the plunger is textured to improve the friction performance.The main work is as follows:(1)Based on numerical simulation,the oil film thickness and oil film pressure distribution between the plunger and the cylinder block under different angles are studied,the plunger pressure zoning model is established,and the micro texture optimization design is carried out for the high oil pressure area,and the influence law of micro texture parameters on oil film thickness and oil film pressure is discussed.The results show that the micro texture design in the high oil pressure zone can increase the peak oil film pressure at different angles,and the textured oil film thickness is reduced compared with the non textured oil film thickness.By increasing the oil film pressure,and then improving the oil film bearing capacity,it is helpful for the plunger to enter the fluid lubrication state.The texture diameter is 0.3 mm,the texture spacing is 0.8 mm,and the texture depth is 60 μm can maximize the oil film pressure.(2)Based on the laser ablation experiment,the morphology change and phase change mechanism model of laser ablation plunger material GCr15 steel are studied,which provides a basis for the preparation of controllable micro texture size.The results show that the laser ablation of GCr15 steel can be divided into four stages.The first stage: when the laser energy density is low,the ablation morphology is micro pits,there is a small amount of molten condensate at the bottom edge of the micro pits,and the phase composition of the molten condensate is mainly carbide;The second stage: the laser energy density increases,the molten condensate gradually accumulates,the micro concave shape changes to the micro convex shape,and the carbon and alloy elements gradually enrich to form more carbides;The third stage: the laser energy density is further increased,forming pits,and the carbides are less than those in the second stage;The fourth stage: at this time,the laser energy density reaches the maximum,the pit morphology becomes extremely irregular,and the carbide is significantly increased compared with the first three stages.(3)On the basis of friction and wear experiments,based on response surface method,the optimal micro texture parameters are discussed,the distribution model of micro texture improving the surface lubrication state of plunger pair is established,and the friction and wear mechanism is analyzed.The results show that the texture diameter is 0.3 mm,the texture spacing is 0.8 mm,and the texture depth is 60 μm has the best friction performance,which verifies the accuracy of the numerical simulation model.Through analysis,it is found that the optimal micro texture parameters improve the friction performance(friction coefficient,wear amount,fractal dimension)of the plunger in the oil pressure area(3 °,90 °,145 °).Under the condition of semi dry friction,the micro texture improves the surface friction performance by storing abrasive particles.Under the condition of boundary lubrication,the effect of micro hydrodynamic lubrication begins to work through secondary lubrication and mixed lubrication,Under the condition of fluid lubrication,the effect of micro hydrodynamic lubrication plays a major role.