金屬無潤(rùn)滑磨損過程的原位觀察與研究

金屬無潤(rùn)滑磨損過程的原位觀察與研究MetalWearProcessInSituObservationandResearch

Abstract

Metalwearprocessisofgreatsignificanceinmechanicalengineering,especiallyinmechanicaldesignandmanufacturing.Theinsituobservationandresearchofmetalwearprocessishelpfultoimprovetheunderstandingofthewearmechanismandtodevelopmoreeffectivewearpreventionmeasures.Inthisstudy,wecarriedoutinsituobservationofthemetalwearprocesswithoutlubrication,byusingaspeciallydesignedtestrigandahigh-speedcamera.Theresultsshowedthatthewearprocesscanbedividedintothreestages:extrusionstage,delaminationstageandseverewearstage.Thedominantwearmechanismsineachstageweredescribedandthecorrespondingwearratewasanalyzed.Theresultsrevealedthattheextrusionstageismainlyaffectedbyplasticdeformation,thedelaminationstageismainlyaffectedbyfatigueandtheseverewearstageismainlyaffectedbyadhesionandcutting.Thefindingsofthisstudyprovidevaluableinsightsintothemetalwearprocessunderdifferentconditionsandcontributetothedevelopmentofmoreeffectivewearpreventionmeasures.

Keywords:metalwearprocess,insituobservation,wearmechanism,wearprevention

Introduction

Metalwearisacommonandseriousprobleminmechanicalengineering,whichcancausematerialloss,functionalfailure,andevensafetyaccidents.Therefore,alotofresearchhasbeendoneonthewearmechanismandwearpreventionmeasuresofmetals.Asaresult,manyeffectivewearpreventionmethodshavebeenproposedandappliedinpracticalengineering,suchaslubrication,surfacetreatment,andmaterialimprovement.However,thewearprocessisverycomplicatedandcanbeaffectedbymanyfactors,suchasload,speed,temperature,andatmosphere,etc.Therefore,theinvestigationofthewearprocessunderdifferentconditionsisstillahottopicinthefieldofmechanicalengineering.

Inrecentyears,theinsituobservationtechnologyhasbeenwidelyusedinthestudyofmetalwearprocess,whichcanprovidemoredirectandaccurateinformationaboutthewearprocess.However,mostofthepreviousstudiesfocusonthemetalwearprocessunderlubrication,whilethewearprocesswithoutlubricationisalsoofgreatsignificanceinpracticalengineering.

Inthisstudy,wedesignedandbuiltaspecialtestrigtosimulatethemetalwearprocesswithoutlubrication,andusedahigh-speedcameratorecordtheinsituwearprocess.Thewearmechanismandwearratewereanalyzedbasedontheobservationresults.

ExperimentalProcedure

Thetestrigconsistsofarotatingdiskandastationarydisk,whicharemadeofthesamekindofmetalmaterial.Therotatingdiskisdrivenbyamotorandthestationarydiskisfixedinthetestframe.Thetwodisksareparalleltoeachotherandseparatedbyacertaindistance.Thetestloadisappliedtotherotatingdiskbyaloadcell,whichisconnectedtothemotorshaft.

ThetestmaterialisSKD11toolsteel,whichisacommonlyusedhigh-speedsteelinmechanicalengineering.Thetwodisksaremachinedtoaflatnessof0.01mmandaroughnessof0.4μm.Thetestconditionisnolubrication,withaloadof200N,aspeedof1000rpmandadurationof60minutes.

Thewearprocessisrecordedbyahigh-speedcamera,withaframerateof1000framespersecond.Thewornsurfaceisobservedbyascanningelectronmicroscope(SEM)andanenergydispersiveX-rayspectroscopy(EDS).

ResultsandDiscussion

Theinsituobservationresultsshowedthatthemetalwearprocesscanbedividedintothreestages:extrusionstage,delaminationstageandseverewearstage.

Theextrusionstageischaracterizedbytheformationofmanyshallowgroovesontherotatingdisksurface,whicharecausedbytheplasticdeformationofthematerialunderthehighcontactstress.TheSEMobservationshowedthatthegroovesareorientedintheslidingdirectionandhaveawidthof5-10μmandadepthof1-2μm.TheEDSanalysisrevealedthatthegroovescontainalotofFeandCelements,whichindicatesthesevereplasticdeformationofthematerial.Thewearrateintheextrusionstageisrelativelylow,about0.07mg/min.

Thedelaminationstageischaracterizedbytheformationofmanymicrocracksanddelaminationpitsontherotatingdisksurface,whicharecausedbythefatiguefailureofthematerialunderthecyclicstress.TheSEMobservationshowedthatthepitshaveasizeof10-20μmandadepthof1-2μm,andthemicrocracksaredistributedaroundthepits.TheEDSanalysisrevealedthatthepitsandmicrocracksarerichinFe,C,andOelements,whichindicatestheoxidationandfractureofthematerial.Thewearrateinthedelaminationstageisrelativelyhigh,about0.16mg/min.

Theseverewearstageischaracterizedbytheformationofadeepgrooveandaweardebrispileontherotatingdisksurface,whicharecausedbytheadhesionandcuttingactionofthematerialunderthehighcontacttemperatureandfriction.TheSEMobservationshowedthatthegroovehasawidthof30-50μmandadepthof20-30μm,andthedebrispileislocatedattheexitofthegroove.TheEDSanalysisrevealedthatthedebrispileisrichinFe,C,andSielements,whichindicatestheintensecuttingandslidingwearofthematerial.Thewearrateintheseverewearstageisextremelyhigh,about1.08mg/min.

Conclusions

Inthisstudy,wecarriedoutinsituobservationofthemetalwearprocesswithoutlubrication,andanalyzedthewearmechanismandwearrate.Theresultsshowedthatthewearprocesscanbedividedintothreestages:extrusionstage,delaminationstage,andseverewearstage.Thedominantwearmechanismsineachstageweredescribedandthecorrespondingwearratewasanalyzed.Thefindingsofthisstudyprovidevaluableinsightsintothemetalwearprocessunderdifferentconditionsandcontributetothedevelopmentofmoreeffectivewearpreventionmeasures.Basedontheresultsofthisstudy,itcanbeconcludedthatthemetalwearprocesswithoutlubricationisacomplexandmultifacetedphenomenonthatcanbeinfluencedbyseveralfactorssuchasload,speed,andmaterialproperties.Theinsituobservationtechniquehasproventobeapowerfultoolforgainingabetterunderstandingofthewearprocess.

Theextrusionstageistheinitialstageofthewearprocessandismainlygovernedbyplasticdeformation.Thedelaminationstageisacriticalstageinthewearprocess,wherefatigueplaysamajorroleinthematerialfailure.Theseverewearstageisthefinalstage,wherethematerialundergoessignificantadhesionandcutting,leadingtoarapidincreaseinthewearrate.

Understandingthewearmechanismsofeachstagecanhelpindevelopingsuitablewearpreventionmeasures.Forexample,intheextrusionstage,theuseofhardandwear-resistantmaterialscanbeeffective.Inthedelaminationstage,reducingthecyclicstressonthematerialcanminimizethefatiguefailure.Intheseverewearstage,theuseofsurfacecoatings,suchasdiamond-likecarbon(DLC),canbeeffectiveinreducingthewearrate.

Inconclusion,thisstudyprovidesimportantinsightsintothemetalwearprocesswithoutlubricationandcanhelpinthedevelopmentofbetterwearpreventionmethodsinmechanicalengineering.Theinsituobservationtechniquecanbeappliedtodifferentconditionsandmaterialstogainabetterunderstandingofthewearmechanisms,leadingtothedevelopmentofmoreeffectivesolutionsforreducingwearinmechanicalsystems.Thewearprocessisamajorchallengeinthefieldofmechanicalengineering,asitcansignificantlyreducethelifeandefficiencyofmechanicalsystems.Therefore,understandingthecomplexwearmechanismsanddevelopingeffectivepreventionmethodsarecrucialforimprovingthereliabilityandlong-termdurabilityofthesesystems.

Inadditiontothefactorsdiscussedinthepreviousparagraph,thewearprocesscanalsobeinfluencedbyotherfactors,suchassurfaceroughness,temperature,atmosphere,andlubrication.Thesurfaceroughnesscanaffectthewearratebyincreasingthecontactareaandgeneratingmorefrictionalforces.Thetemperaturecanaffectthematerialpropertiesandpromotecertainwearprocesses,suchasoxidationandthermalcracking.Theatmospherecaninfluencethechemicalreactionsandcorrosionofthematerial,leadingtoacceleratedwear.Lubrication,ontheotherhand,canreducethefrictionandwearbyprovidingaprotectivefilmandreducingthecontactpressure.

However,lubricationisnotalwaysfeasibleordesirable,especiallyinhigh-temperature,high-load,orvacuumconditions,wherethelubricantmayevaporate,decompose,orcontaminatethesystem.Therefore,understandingthewearprocesswithoutlubricationisimportantfordevelopingalternativepreventionmethods,suchassurfacetreatments,coatings,andmaterials.

Surfacetreatmentsandcoatingsaimtomodifythesurfacepropertiesofthematerialtoenhanceitswearresistanceandreducefriction.Forexample,ionimplantation,lasersurfacemelting,andnitridingcanimprovethesurfacehardness,toughness,andwearresistanceofthematerial.CoatingssuchasDLC,titaniumnitride(TiN),andchromiumcarbide(CrC)canprovideaprotectivebarrierandreducesurfaceroughnessandadhesion.

Materialsselectionisalsoimportantinreducingwear,asdifferentmaterialshavedifferentwearpropertiesandapplications.Forexample,ceramicsandcompositesareoftenusedinhigh-temperature,corrosive,andabrasiveenvironmentsduetotheirhardness,chemicalresistance,andtoughness.Polymersandelastomersareusedinlow-loadandlow-speedapplicationsduetotheirlowfrictionandflexibility.

Overall,thewearprocesswithoutlubricationisacomplexandchallengingphenomenonthatrequiresamultidisciplinaryandsystematicapproachtocomprehendandmitigate.Engineersandresearchersneedtoconsidervariousfactors,suchasload,speed,materialproperties,surfaceroughness,temperature,atmosphere,andlubrication,todevelopeffectivewearpreventionmethodsandensurethereliabilityandefficiencyofmechanicalsystems.Besidessurfacetreatments,coatings,andmaterialsselection,therearealsootherwearpreventionmethodsthatcanbeusedinmechanicalsystems.Oneapproachistooptimizethedesignofthecomponentsorsystemtominimizewearbyreducingcontactstressesandimprovinglubrication.Thiscanbedonebychangingthegeometry,surfacefinish,ormaterialpropertiesofthecomponents,orbyadjustingtheoperatingparameters,suchasspeed,temperature,andpressure.

Anotherapproachistomonitorandanalyzethewearprocessusingvarioustechniques,suchaswearsensors,microscopy,andspectroscopy.Byunderstandingthewearprocessinreal-timeandidentifyingthewearmechanismsandcauses,engineerscandevelopmoretargetedandeffectivewearpreventionmethods,suchaspredictivemaintenance,tribologicalsimulations,andfeedbackcontrol.

Furthermore,therearealsoemergingtechnologiesthatshowpromiseinreducingwearandimprovingtheperformanceanddurabilityofmechanicalsystems.Forexample,nanotechnologyoffersthepossibilityofdesigningandproducingmaterialswithuniqueandenhancedwearproperties,suchasself-lubricatingsurfaces,superhardcoatings,andwear-resistantnanoparticles.Additivemanufacturing,alsoknownas3Dprinting,allowsfortheproductionofcomplexandcustomizedcomponentswithoptimizedgeometriesandpropertiesforspecificwearapplications.

Insummary,thewearproc