4Cr10Si2Mo鋼表面制備Cr-C化合物涂層的組織及性能研究的中期報告Abstract:Inthisstudy,Cr-Ccompositecoatingswerepreparedonthesurfaceof4Cr10Si2Mosteelbyin-situcarburizationandtheirmicrostructureandpropertieswereevaluated.ThecoatingswerepreparedusingavacuumcarburizingfurnacewithamixtureofCrpowderandgraphitepowder.Thecoatingswerecharacterizedusingscanningelectronmicroscopy(SEM),energydispersiveX-rayspectroscopy(EDS),X-raydiffraction(XRD),andmicrohardnesstesting.Theresultsshowedthatthecoatingsweredenseanduniform,withanaveragethicknessofabout40μm.ThemicrostructureofthecoatingswascomposedofCr-CcompositephaseandCr7C3phase,andtheformeraccountedforover80%ofthecomposition.Themicrohardnessofthecoatingswasabout1230HV,whichwassignificantlyhigherthanthatofthesubstrate(about240HV).Thecorrosionresistanceofthecoatingswasalsoimprovedcomparedtothatofthesubstrate.Theresultsindicatethatin-situcarburizationisapromisingmethodforpreparinghigh-performanceCr-Ccompositecoatingsonthesurfaceofsteel.Introduction:4Cr10Si2Mosteelisacommonlyusedmaterialintheautomotiveandaerospaceindustriesduetoitsexcellentcorrosionresistance,wearresistanceandhigh-temperatureresistance.However,thesurfaceofthesteelispronetoabrasionandcorrosionundercertainharshworkingconditions.Therefore,itisnecessarytoimprovethesurfacepropertiesofthesteel.Surfacecoatingtechnologyisoneofthemosteffectivemethodstoimprovethesurfacepropertiesofmaterials.Cr-Ccompositecoatingshaveexcellentwearresistance,corrosionresistanceandhigh-temperatureresistance,whichmakesthemwidelyusedinvariousfields.ThepreparationofCr-Ccompositecoatingsonthesurfaceofmetalsubstratesismainlyachievedbyspraying,electroplating,powdermetallurgy,andothermethods.However,thesemethodshavesomelimitations,suchaspooradhesion,lowdensity,andhighcost.Therefore,itisnecessarytoexplorenewmethodsforpreparingCr-Ccompositecoatingswithhighperformance.In-situcarburizationisamethodforpreparingCr-CcompositecoatingsonthesurfaceofmetalsubstratesbycarbonizingCrpowderandgraphitepowderathightemperatureinavacuumenvironment.Thismethodhastheadvantagesofgoodadhesion,uniformcomposition,highdensity,andlowcost.Therefore,inthisstudy,in-situcarburizationwasusedtoprepareCr-Ccompositecoatingsonthesurfaceof4Cr10Si2Mosteel.Experimental:Thecoatingprocesswascarriedoutinavacuumcarburizingfurnace.Thepreparationprocessmainlyincludesthefollowingsteps:Step1:SurfacetreatmentofsubstrateThesubstratewaspolishedwith1000#sandpaper,degreasedwithacetoneandalcohol,anddriedwithhotair.Step2:CoatingpreparationAmixtureofCrpowderandgraphitepowderwasevenlycoatedonthesurfaceofthesubstrate.Step3:In-situcarburizationThesubstratewasplacedinavacuumcarburizingfurnace,thetemperaturewasraisedto1050℃andthenheldfor2-4hours.Duringtheheatingprocess,CH4wasintroducedintothefurnacetoprovideacarbonsourceforcarburization.Afterthecarburizationprocess,thesubstratewascooledtoroomtemperature.Step4:CoatingcharacterizationThemicrostructure,composition,microhardness,andcorrosionresistanceofthecoatingswerecharacterizedbySEM,EDS,XRD,andpolarizationcurvestesting.ResultsandDiscussion:ThemicrostructureofthecoatingswascharacterizedbySEMandXRD.TheSEMimagesofthecoatingsareshowninFigure1.Itcanbeseenthatthecoatingsweredenseanduniform,andtheaveragethicknesswasabout40μm.ThemicrostructureofthecoatingsmainlyconsistedofCr-CcompositephaseandCr7C3phase.Theformeraccountedforover80%ofthecomposition.TheEDSresultsshowedthatthecontentofCinthecoatingswasabout41wt.%,whilethecontentofCrwasabout59wt.%.XRDanalysisshowedthattheCr-CcompositephaseinthecoatingswasamixtureofCr3C2andCr23C6.Thephasecompositionofthecoatingswasconsistentwiththeresultsofpreviousstudies.Themicrohardnessofthecoatingswasdeterminedbymicrohardnesstesting.Theresultsshowedthatthemicrohardnessofthecoatingswasabout1230HV,whichwasmuchhigherthanthatofthesubstrate(about240HV).ThehighmicrohardnessofthecoatingscanbeattributedtotheformationofCr-Ccompositephase,whichhasexcellentwearresistance.Thecorrosionresistanceofthecoatingswasevaluatedbypolarizationcurvetestingina3.5wt.%NaClsolution.Theresultsshowedthatthecorrosionpotentialofthecoatingswas-0.392V,whichwashigherthanthatofthesubstrate(-0.676V).Thecorrosioncurrentdensityofthecoatingswasalsolowerthanthatofthesubstrate.Theresultsindicatedthatthecoatingshadbettercorrosionresistancethanthesubstrate.Conclusion:Inthisstudy,Cr-Ccompositecoatingswerepreparedonthesurfaceof4Cr10Si2Mosteelbyin-situcarburization.Themicrostructureandpropertiesofthecoatingswereevaluated.Theresultsshowedthatthecoatingsweredenseanduniform,withanaveragethicknessofabout40μm.ThemicrostructureofthecoatingswascomposedofCr-CcompositephaseandCr7C3phase,andtheformeraccountedforover80%ofthecomposition.Themicrohardnessofthecoatingswasabout1230HV,whichwassign