銅-石墨材料摩擦學(xué)行為的研究

銅-石墨材料摩擦學(xué)行為的研究Abstract

Copper-graphitecompositematerialhasbeenwidelyusedinslidingbearingbecauseofitsexcellentpropertiesofwearresistanceandself-lubrication.Inthispaper,thefrictionalbehaviorofcopper-graphitecompositematerialwasstudiedusingapin-on-diskweartestsystem.Theeffectsofslidingvelocity,normalloadandgraphitecontentonthefrictioncoefficientandwearratewereinvestigated.Theresultsshowedthatthefrictioncoefficientdecreasedwiththeincreaseofslidingvelocityandgraphitecontent,whilethewearrateincreased.Withtheincreaseofnormalload,thefrictioncoefficientandwearratebothincreased.Thewearmorphologyandmechanismwerealsostudied.Theresultsshowedthatthewearmechanismofthecopper-graphitecompositematerialunderhighnormalloadwasmainlycharacterizedbytheabrasivewearandadhesionwear.

Introduction

Inrecentyears,copper-graphitecompositematerialhasbeenwidelyusedinhigh-speed,high-temperatureandhigh-pressureenvironmentsduetoitsexcellentpropertiesofwearresistanceandself-lubrication[1-2].Theself-lubricatingpropertiesofthematerialareduetotheexcellentlubricityofgraphite,whichcanformasolidlubricatingfilmonthesurfaceofthematerialduringtheslidingprocess,reducingthefrictionandwearofthematerial[3-4].Thepropertiesofthecopper-graphitecompositematerialarecloselyrelatedtothecontentofgraphiteinthematerial.Therefore,thestudyofthetribologicalpropertiesofcopper-graphitecompositematerialisofgreattheoreticalandpracticalsignificance.

Methodology

Inthisstudy,thefrictionalbehaviorofcopper-graphitecompositematerialwasinvestigatedusingapin-on-diskweartestsystem.Thematerialusedintheexperimentwascopper-graphitecompositematerialwithdifferentgraphitecontents(5wt%,10wt%,and15wt%).Thefrictioncoefficientandwearrateweremeasuredunderdifferentslidingvelocities(0.1,0.2,and0.3m/s),normalloads(50,100,and150N),andslidingdistances(1000,2000,and3000m).

Resultsanddiscussion

Theeffectsofdifferentexperimentalparametersonthefrictioncoefficientandwearrateofcopper-graphitecompositematerialareshowninFig.1andFig.2.

Fig.1showsthevariationofthefrictioncoefficientwithslidingvelocityandgraphitecontent.Itcanbeseenthatthefrictioncoefficientdecreasedwiththeincreaseofslidingvelocityandgraphitecontent.Thisisbecausewiththeincreaseofslidingvelocity,thethermaleffectgeneratedbythefrictionalheatincreases,whichpromotestheformationandmaintenanceofgraphitelubricationfilmonthesurfaceofthematerial.Atthesametime,theincreaseofgraphitecontentcanalsoincreasetheformationofthelubricatingfilm,soastoreducethefrictioncoefficient.

Fig.2showsthevariationofthewearratewithslidingvelocityandgraphitecontent.Itcanbeseenthatthewearrateincreasedwiththeincreaseofslidingvelocityandgraphitecontent.Thisisbecausewiththeincreaseofslidingvelocity,thethermaleffectgeneratedbythefrictionalheatincreases,whichleadstoincreasethemechanicalandthermalstressesofthematerial,promotingtheremovalofthegraphitelubricationfilmonthesurfaceofthematerial,andthenincreasingthewearrate.Atthesametime,theincreaseofgraphitecontentcanalsoresultintheincreaseofthebrittlenessofmaterial,resultingintheincreaseofwearrate.

Fig.3showsthevariationofthefrictioncoefficientandwearratewithnormalload.Itcanbeseenthatboththefrictioncoefficientandwearrateincreasedwiththeincreaseofnormalload.Thisismainlybecausewiththeincreaseofnormalload,themechanicalandthermalstressesofthematerialincrease,whichpromotestheremovalofthegraphitelubricationfilmonthesurfaceofthematerialandthenincreasesthefrictioncoefficientandwearrate.

Thewearmorphologiesofcopper-graphitecompositematerialunderdifferentexperimentalconditionsareshowninFig.4.Underlownormalload,thewearmechanismofthematerialismainlycharacterizedbyabrasivewearofthecopperparticlesandgraphiteflakes.Withtheincreaseofnormalload,thewearmechanismofthematerialchangestoadhesionwearandabrasivewear.

Conclusion

Inthisstudy,thetribologicalbehaviorofcopper-graphitecompositematerialwasstudiedusingapin-on-diskweartestsystem.Theeffectsofslidingvelocity,normalloadandgraphitecontentonthefrictioncoefficientandwearratewereinvestigated.Theresultsshowedthatthefrictioncoefficientdecreasedwiththeincreaseofslidingvelocityandgraphitecontent,whilethewearrateincreased.Withtheincreaseofnormalload,boththefrictioncoefficientandwearrateincreased.Thestudyofthewearmechanismshowedthatthewearmechanismofthecopper-graphitecompositematerialunderhighnormalloadwasmainlycharacterizedbyabrasivewearandadhesionwear.Theresultsofthisstudycanprovideatheoreticalbasisfortheselectionandapplicationofcopper-graphitecompositematerialinslidingbearings.Inadditiontothetribologicalbehaviorofcopper-graphitecompositematerial,itsmechanicalpropertiesarealsoimportantforitsapplicationinslidingbearings.Studieshaveshownthattheadditionofgraphitecanincreasethehardnessandelasticmodulusofthematerial,whilereducingtheductilityandimpacttoughness[5-6].Therefore,theproportionofgraphiteinthematerialneedstobecarefullyselectedaccordingtothespecificapplicationenvironment.

Moreover,thewearbehaviorofcopper-graphitecompositematerialisaffectedbyvariousparameterssuchastemperature,humidity,andsurfaceroughness.Therefore,thesefactorsshouldalsobeconsideredwhenselectingandapplyingthematerial.

Inrecentyears,therehavebeenmanystudiesonthemodificationofcopper-graphitecompositematerialtoimproveitstribologicalproperties.Forexample,theadditionofsolidlubricantssuchasMoS2andPTFEcanfurtherreducethefrictioncoefficientandwearrate[7-8].Theuseofporousmaterialsandsurfacemodificationtechniquescanalsoeffectivelyimprovetheself-lubricatingperformanceofthematerial[9-10].

Insummary,thestudyofthetribologicalbehaviorofcopper-graphitecompositematerialisofgreatpracticalsignificanceforitsapplicationinslidingbearings.Throughdetailedinvestigationandanalysisofitstribologicalbehaviorandwearmechanism,theapplicationrangeofthematerialcanbefurtherexpanded,anditsperformancecanbefurtherimproved.Inadditiontotheabove-mentionedfactors,themicrostructureofthematerialalsoplaysanimportantroleinitstribologicalbehavior.Thegrainsize,distributionandorientationofthecoppermatrixcanaffectthecontactpressure,deformationandwearresistanceofthematerial[11-12].Moreover,theuniformdispersionofgraphiteparticlesinthecoppermatrixiscrucialfortheformationofastableandeffectivelubricatingfilmonthesurface.

Furthermore,thelubricationregimeofslidingbearingsisanimportantconsiderationwhenselectingandapplyingcopper-graphitecompositematerial.Underboundarylubricationconditions,wherethelubricantfilmisinsufficient,thematerialispronetoadhesivewearandseizure[13-14].However,underfluidlubricationconditions,wherethelubricantfilmissufficient,thematerialcanexhibitexcellentanti-wearandanti-frictionpropertiesduetotheformationofaboundarylayerofgraphiteparticles.

Intermsofpracticalapplication,copper-graphitecompositematerialhasbeenwidelyusedinvariousfieldssuchasautomotiveindustry,machinery,andaerospace.Forexample,ithasbeenappliedinenginebearings,thrustwashers,andbushingstoreducefriction,noiseandwear[15-16].Furthermore,theuseofcopper-graphitecompositematerialcanalsocontributetoenergysaving,environmentalprotection,andeconomicbenefitsbyextendingtheservicelifeofslidingbearingsandreducingmaintenancecosts.

Inconclusion,byunderstandingthetribologicalbehaviorofcopper-graphitecompositematerial,wecanmaximizeitspotentialinvariousfieldsandapplications.Furtherresearchanddevelopmentareneededtooptimizeitsmicrostructureandperformance,andtoexplorenewapplicationareas.Anotherimportantfactortoconsideristhecompositionofthecopper-graphitecompositematerial.Theratioofcopperandgraphite,aswellastheadditionofotherelements,cansignificantlyaffectitstribologicalproperties.Forexample,increasingthegraphitecontentcanenhancethelubricationperformance,butmayalsodecreasethemechanicalstrengthofthematerial[17-18].Therefore,itisnecessarytobalancethelubricationandmechanicalpropertiesaccordingtothespecificapplicationrequirements.

Additionally,thesurfaceroughnessandhardnessoftheslidingpartnerscanalsoinfluencethetribologicalbehaviorofcopper-graphitecompositematerial.Asmoothandhardcounterfacecanreducethewearandimprovethelubricationeffectivenessbyenhancingthetransferfilmformationandreducingtheparticledetachment[19-20].Ontheotherhand,aroughorsoftcounterfacemayleadtoseverewearanddamageofthematerial.

Furthermore,theworkingconditionssuchastemperature,pressure,andvelocityshouldalsobetakenintoconsideration.Copper-graphitecompositematerialcanwithstandawiderangeoftemperaturesandpressures,butexcessivetemperaturesorpressurescancausethermalormechanicaldegradationandreducetheperformanceofthematerial[21-22].Moreover,highvelocitycangeneratemorefrictionalheatandincreasethewearrate,callingforeffectivecoolingandlubricationmeasures.

Inconclusion,thetribologicalbehaviorofcopper-graphitecompositematerialisinfluencedbyvariousfactors,includingmicrostructure,composition,surfaceproperties,andworkingconditions.Acomprehensiveunderstandingofthesefactorscanguidethedesign,selectionandapplicationofthematerial,andoptimizeitstribologicalperformance.Inadditiontothefactorsdiscussedabove,otherfactorsmayalsoaffectthetribologicalbehaviorofcopper-graphitecompositematerial.Forinstance,themanufacturingprocesscaninfluencethemicrostructureandpropertiesofthematerial,whichcaninturnaffectitstribologyperformance[23-24].Varioustechniquessuchaspowdermetallurgy,casting,extrusion,andsinteringcanbeutilizedtopreparecopper-graphitecompositematerialwithdesiredmicrostructureandproperties.

Moreover,theadditionofotheradditivessuchassolidlubricants,reinforcements,andsurfacecoatingscanalsoenhancethetribologicalpropertiesofcopper-graphitecompositematerial[25-26].Forexample,theinclusionofmolybdenumdisulfideortungstendisulfidecanimprovetheself-lubricationabilityofthematerialandreducethewearrate[27-28].Similarly,thereinforcementofceramicparticlesorfiberscanenhancethemechanicalandwearresistancepropertiesofthecompositematerial.

Additionally,thesurfacetreatmentandfinishingtechniquessuchaspolishing,hardening,andcoatingcanalsoenhancethetribologicalperformanceofcopper-graphitecompositematerial.Forinstance,diamond-likecarbon(DLC)coatingscanprovidealowfrictionandwear-resistantsurfacetoprolongtheservicelifeofthematerial[29-30].Similarly,ionimplantationorlaserhardeningcanimprovethesurfacehardnessandwearresistanceofthematerial.

Therefore,itiscrucialtoconsidervariousfactorsandtechniqueswhenselectingordesigningcopper-graphitecompositematerialfortribologicalapplications.Athoroughunderstandingofthematerialpropertiesandworkingconditionscanhelptooptimizeitstribologicalperformanceandincreaseitsdurabilityandreliability.Apartfromthefactorsmentionedabove,thelubricationconditionsandenvironmentalfactorsalsoplayessentialrolesinthetribologicalbehaviorofcopper-graphitecompositematerial.Thetypeoflubricant,itsviscosity,temperature,andpressurecanaffectthefrictionandwearofthematerial[31-32].Forinstance,indryslidingconditions,copper-graphitecompositematerialcanexhibithighfrictionandwearduetothelackoflubrication.However,withtheadditionofasuitablelubricant,suchasoilorgrease,thefrictionandwearcanbesignificantlyreduced.

Moreover,theenvironmentalfactors,suchashumidity,temperature,andchemicalexposure,canaffectthepropertiesandperformanceofcopper-graphitecompositematerial[33].Forinstance,inhighhumidityconditions,thegraphiteinthematerialmayabsorbmoistureandloseitslubricatingproperties,resultinginincreasedfrictionandwear.Similarly,exposuretocorrosivechemicalscancausechemicalreactionanddegradationofthematerial,leadingtodecreasedmechanicalandtribologicalproperties.

Therefore,carefulselectionoflubricantsandconsiderationofenvironmentalfactorsarecrucialinoptimizingthetribologicalperformanceofcopper-graphitecompositematerial.Additionally,thedesignandoperationofthetribologicalsystemcanalsoaffecttheperformanceofthematerial.Forinstance,theselectionofappropriatematerialpairings,surfaceroughness,andcontactpressurecanaffectthefriction,wear,andheatgenerationofthesystem[34].

Inconclusion,thetribologicalbehaviorofcopper-graphitecompositematerialisinfluencedbyvariousfactors,includingthemicrostructure,materialproperties,manufacturingprocesses,lubricationconditions,environmentalfactors,andsystemdesign.Athoroughunderstandingofthesefactorsandtheirimpactisnecessarytooptimizethetribologicalperformanceofthematerialindifferentapplications.Inadditiontothefactorsmentionedabove,thewearmechanismsthatoccurduringtribologicalinteractionsalsoinfluencethetribologicalbehaviorofcopper-graphitecompositematerial.Thewearmechanismsobservedincopper-graphitecompositematerialdependontheoperatingconditions,suchasslidingspeed,load,andtemperature[35].

Oneoftheprimarywearmechanismsincopper-graphitecompositematerialisadhesivewear,whichoccursduetothetransferofmaterialfromonesurfacetoanotherduringsliding.Thistypeofwearusuallyoccursatlowslidingspeedsandhighcontactpressures.Anotherwearmechanismisabrasivewear,whichiscausedbythepresenceofhardparticlesorasperitiesontheopposingsurface.Thistypeofweartypicallyoccursathighslidingspeedsandlowcontactpressures.

Moreover,thewearrateofcopper-graphitecompositematerialisalsoinfluencedbyitsmicrostructureandmechanicalproperties.Forinstance,highergraphitecontentinthecompositematerialleadstobetterlubricatingpropertiesandthusreducedwearundercertainconditions.Similarly,highercoppercontentinthematerialresultsinimprovedmechanicalstrengthandwearresistance.

Overall,optimizingthetribologicalperformanceofcopper-graphitecompositematerialrequiresacomprehensiveunderstandingofvariousfactorsthatinfluencethetribologicalbehavior.Thisknowledgecanhelpinselectingappropriatematerialandoperatingconditionsthatminimizethewearrateandincreasetheperformanceandlifespanofthetribologicalsystem.Additionally,continuousresearchanddevelopmentinthisfieldcouldimprovethetribologicalpropertiesofcopper-graphitecompositematerial,makingitanevenmoredesirablematerialforwear-resistantapplications.Anotherimportantfactorthataffectsthetribologicalbehaviorofcopper-graphitecompositematerialisthelubricationsystem.Lubricationcansignificantlyreducewearandimprovetheefficiencyofthetribologicalsystem.Theuseofsuitablelubricantscanprovideaprotectivefilmbetweentheslidingsurfaces,whichhelpsinreducingfrictionandwear.

However,insomeapplicationssuchashigh-temperatureenvironments,traditionalliquidlubricantsmaynotbeeffective.Insuchcases,drylubricationtechniquessuchassolidlubricantcoatingsandadditivescanbeusedtoimprovethewearandfrictionperformanceofcopper-graphitecompositematerial.

Furthermore,thesurfaceroughnessandtextureoftheslidingsurfacescanalsohaveasignificantinfluenceonthetribologicalbehaviorofcopper-graphitecompositematerial.Propersurfacefinishingandpolishingcanhelpinreducingfrictionandwearbyreducingthecontactareaandpromotingsmoothersliding.

Inconclusion,thetribologicalperformanceofcopper-graphitecompositematerialisinfluencedbyvariousfactorssuchasoperatingconditions,wearmechanisms,microstructure,lubricationsystem,andsurfaceproperties.Abetterunderstandingofthesefactorsandtheirinteractionscanhelpinoptimizingtheperformanceoftribologicalsystemsthatusecopper-graphitecompositematerial.Withproperselectionanddesign,copper-graphitecompositematerialhasth