Research On Impact-sliding Wear Mechanism Of Several Material Pairs With Typical Surface Properties

Impact-sliding wear is a typical form of composite wear,which is widely existed in mechanical equipment and parts in many fields such as machinery manufacturing,railway transit,automobiles,and tunnelling machines.The impact-sliding wear easily causes shear deformation,spalling and even cracking of the material and is the direct cause of rapid failure of parts in many working conditions that seriously affects the operation safety and service life of the equipment.However,as the impact-sliding wear is the coupling effect of the two movements of impact and sliding,the motion of impact-sliding is complex and the test parameters are difficult to control.At present,there are relatively few studies on the impactsliding wear,and the uniform impact-sliding wear mechanism of materials has not been formed.Especially,there is a lack of systematic study on the impact-sliding wear mechanism of materials with different surface properties.Therefore,the study on the impact-sliding wear behavior and mechanism of materials with different surface properties not only has important scientific significance but also has great application value and guiding significance in engineering.Detailed failure analysis of the positioning hook and support failure parts used for highspeed railway catenary due to the impact-sliding wear was conducted in this paper.Based on the self-developed impact-sliding wear test device,the systematic impact-sliding wear tests were carried out on several typical surface properties.Then,the impact-sliding wear behavior and mechanism of aluminum alloy/aluminum alloy,aluminum alloy/LSP aluminum alloy,ceramic/hard alloy,ceramic/PVD coatings were studied.Based on the impact-sliding wear mechanism of typical surface characterization materials,the effects of surface properties on the impact-sliding wear behavior and mechanism were discussed,and suggestions for mitigating the impact-sliding wear of materials were provided.The main accomplished research and the chief conclusions are as followed.1.Failure analysis of positioning hook and support parts used for high-speed railway catenary(1)The hook-and-loop structure took a severe stress concentration at the joint,causing the material to rapidly form spalling,and caused the relative motion at the joint to be impactsliding.(2)The hook and loop structure used in the limit positioning device was the essential cause of impact-sliding wear failure at the joint.Therefore,it is suggested to optimize the connection structure of the localizer and the support(such as pin connection)to improve the stress concentration and wear form at the joint.(2)The main damage forms of the positioning hook and support were the spalling and ploughing,and the wear mechanisms were mainly fatigue wear and abrasive wear.2.Developed an impact-sliding wear test device that could control the structural stiffness of the tribology systemBased on the results of failure analysis,a new type of friction and wear test device that could control the structural stiffness of the friction system was successfully developed to realize the experimental simulation of the impact-sliding wear process.Its repeatability and effectiveness have been verified.3.Study on the impact-sliding wear mechanism of several typical surface properties(1)The aluminium alloy material with lower hardness showed seriously damaged under the impact-sliding wear condition,and the main damage forms corresponding to different positions in different stages of the wear scar exhibited obvious differences.The impact zone of the wear scar was mainly subjected to the impact load.Under the cyclic tensile and compressive stress of the subsurface of the material,the damage mechanism of this zone was mainly severe fatigue spalling.The sliding zone of the wear scar was mainly subjected to a varying compressive load with tangential sliding,then the shear stress of the subsurface of the material was further approached to the contact surface.The main damage mechanism of this zone was the ploughing caused by abrasive wear.(2)The impact-sliding wear damage of LSPed aluminium alloy was obviously improved,especially the damage of the impact zone was obviously reduced.The impact-sliding wear mechanism of LSPed aluminium alloy still showed spalling and ploughing,but the resistance of LSP aluminium alloy to spalling damage was greatly increased.This was mainly due to the grain refinement of the surface layer of the material,the formation of residual compressive stress,and the improvement of surface hardness caused by LSP.(3)High hardness cemented carbide materials performed significantly lower impactsliding wear damage than aluminium alloy materials.The main damage to the impact-sliding wear of cemented carbide materials was concentrated in the impact zone where spalling damage and black oxidized wear debris were observed.The damage in the sliding zone was very slight and showed a ‘polishing effect'.The main damage mechanisms of cemented carbide materials were fatigue spalling and certain oxidative wear.(4)The impact-sliding wear behavior and mechanism of the PVD hard coatings were consistent with those of the cemented carbide material,that is,the spalling damage was observed in the impact zone and the “polishing effect” was exhibited in the sliding zone with a slight wear damage.The wear damage of the PVD hard coatings was close to that of the cemented carbide material,thus the hard coat treatment had not significantly improved the impact-sliding wear performance of cemented carbide material.The impact-sliding wear damage of WC/C lubricated coatings was much lighter than that of cemented carbide and hard coatings.Lubricating coatings significantly improved the impact-sliding wear performance of cemented carbide materials.The WC/C coating showed a good reducing effect in both impact and sliding zones for the impact-sliding wear that only a very slight wear was observed in the whole wear scar,and the wear mechanism was abrasive wear.4.Exploring the effect of surface properties of materials on the impact-sliding wear properties(1)Increasing the hardness of the material could reduce the shear damage caused by the sliding load in the impact-sliding wear,which was beneficial to improving the impact-sliding wear performance of the material.However,when the material was high hardness,the high hardness coating that further increased the surface hardness of the material could not continue to effectively enhance the impact-sliding wear resistance of the material.(2)Grain refinement and residual compressive stress on the material surface showed a positive effect on resisting the impact-sliding wear.Thus,surface strengthening technology could significantly improve the impact-sliding wear performance of the material.(3)The lubricating coating could greatly improve the impact-sliding wear performance of the material,and the spalling and ploughing damage caused by the impact-sliding wear was significantly reduced.Therefore,the lubricating materials with good strength and toughness will be a superior choice for improving impact-sliding wear resistance.(4)To improve the impact-sliding wear performance of the material,it was necessary to increase the hardness of the material,meanwhile,to reduce the spalling damage through refining the grain,increasing the residual compressive stress and lubricating.