Tribological Preformance Between The Valve Plate And Cylinder Block In Axial Piston Pump

Axial piston pump is widely used in industrial applications because of its excellent operating performance.Because of the high working pressure,the frictional pairs of the piston pump also need to bear higher loads,which will aggravate the wear of the frictional pairs.The valve plate/cylinder block frictional pair is the largest frictional pair of the axial piston pump,and it is also one of the frictional pairs prone to wear failure.The existing researches on the tribological characteristics of the valve plate/cylinder block frictional pair are mainly carried out on a friction tester under low-speed operating conditions(?1000 r/min).As for the axial piston pump,the cylinder block usually rotates at a speed of 1500 r/min,even up 3000 r/min.In order to make the research results consistent with the actual situation of piston pump,the tribological characteristics of the valve plate/cylinder block frictional pair are studied at high speed.Based on the principle of the axial piston pump,the tribological characteristics of the valve plate/cylinder block frictional pair under the boundary lubrication condition are studied at high rotational speed.During the research,ring-on-disc tester is utilized to investigate the tribological characteristics between the hard materials(38CrMoAl and 42CrMo)for the valve plate under different heat treatment conditions and the soft material for the cylinder block surface(CuPb15Sn5)without any heat treatment.The friction coefficient,wear rate,surface topography and material properties were used to analyze the tribological properties of valve plate/cylinder block.The effects of the rotational speed on the tribological characteristics of the valve plate/cylinder block frictional pair are studied experimentally,and the limit working pressure of the frictional pair is measured by gradually increasing the experimental pressure at high speed.Finally,the effects of heat treatment process on the tribological characteristics of the valve plate/cylinder block are studied under the limit working pressure of the frictional pair.Research suggests that: the lubrication condition of the frictional pair deteriorates and the temperature of the frictional surface increases under high speed,which leads to higher wear rate of the soft material.Therefore,the cylinder block is more prone to adhesive wear at high speed.When the experimental pressure exceeds 2.5 MPa,severe adhesive wear will occur on the surface of frictional pairs and the soft material will transfer to the surface of the hard material formed a transfer film.At that time,the valve plate/cylinder block frictional pair will quickly wear and become invalid.Therefore,the limit working pressure of the valve plate/cylinder block frictional pair at high speed is 2.5 MPa.The heat treatment process has a great impact on the frictional characteristic of the valve plate/cylinder block frictional pair.Increasing the hardness of the valve plate by nitriding treatment will not improve the tribological properties of the valve plate/cylinder block frictional pair.The refined structure produced on the surface of the sample after quenching and tempering can reduce the adhesion of bronze on the surface of the valve plate.Therefore,nitriding treatment after quenching and tempering treatment can improve the tribological characteristics of the valve plate/cylinder block frictional pair.The tribological characteristics of 38 CrMoAl and 42 CrMo are quite different.Under the experimental conditions,38 CrMoAl treated by tempering,quenching and nitriding process has excellent tribological characteristics,and is more suitable as the material of the valve plate.