放電等離子快速燒結C Cu復合材料的組織和摩擦磨損特性研究

放電等離子快速燒結CCu復合材料的組織和摩擦磨損特性研究Abstract:ThepurposeofthisstudyistoinvestigatethemicrostructureandfrictionalwearpropertiesofC/Cucompositematerialsrapidlysinteredbydischargeplasma.TheC/Cucompositeswerefabricatedusingasparkplasmasintering(SPS)methodwithdifferentCuvolumefractions(0-60vol.%).Themicrostructureofthecompositeswascharacterizedbyscanningelectronmicroscopy(SEM)andX-raydiffraction(XRD).Tribologicaltestwascarriedoutonapin-on-disctribometerunderdryslidingconditions.TheresultsshowedthattheC/CucompositesexhibitedadenseanduniformmicrostructurewiththepresenceofCuparticlesuniformlydistributedinaCmatrix.WithincreasingCuvolumefraction,thedensityandthermalconductivityofthecompositesincreased,whilethehardnessandwearresistancedecreased.Thecompositecontaining30vol.%Cushowedthebestfrictionalwearproperties,withthelowestfrictioncoefficientandthesmallestwearrate.Thewearmechanismsofthecompositesweremainlyadhesivewearandabrasivewear.

Keywords:C/Cucomposite;dischargeplasma;microstructure;frictionalwear

Introduction

Carbon/copper(C/Cu)compositematerialspossessexcellentproperties,suchashighstrength,highthermalconductivity,lowdensityandgoodwearresistance.ThesepropertiesmakeC/Cucompositesusefulinmanyapplications,suchaselectricalcontacts,heatsinks,electronicpackagingandaerospaceindustries.VariousmethodshavebeenusedtofabricateC/Cucomposites,includingpowdermetallurgy,infiltration,andhotpressing.However,thesemethodshavesomedisadvantages,suchashightemperature,longsinteringtime,andpoorinterfacialbondingbetweencarbonandcopperphases.Therefore,itisessentialtodeveloparapidandeffectivemethodfortheproductionofC/Cucompositeswithdesirableproperties.

Dischargeplasmasinteringisanovelandeffectivemethodfortherapidconsolidationanddensificationofpowdermaterials.Itisanon-equilibriumprocessthatuseselectricdischargesbetweentwoelectrodestogenerateahightemperatureandhighpressureinapowderbed.Thisleadstotherapidsinteringofpowderparticlesandtheformationofadenseanduniformmicrostructure.Thedischargeplasmamethodhasbeensuccessfullyusedtofabricatevariousmetalandceramiccomposites,suchasAl2O3/TiC,WC-Co,andNi-Ti.However,littleresearchhasbeenconductedonthefabricationofC/Cucompositesusingdischargeplasmasintering.

Inthisstudy,weinvestigatedthemicrostructureandfrictionalwearpropertiesofC/Cucompositesrapidlysinteredbydischargeplasma.TheeffectofCuvolumefractiononthemicrostructureandmechanicalpropertiesofthecompositeswasstudied.Thewearbehaviorandmechanismsofthecompositeswerealsoinvestigated.

Experimental

C/Cucompositeswerepreparedbythesparkplasmasintering(SPS)method.Carbonpowders(particlesize:<10μm)andcopperpowders(particlesize:<5μm)weremixedindifferentvolumefractions(0-60vol.%)andballmilledfor2hinaplanetarymill.Themixedpowderswereloadedintoagraphitediewithaninnerdiameterof30mmandaheightof40mm.Thepowderbedwaspressedunderuniaxialpressureof50MPa,andthenrapidlysinteredusingaSPSfurnace(Labox650,SPSSyntexCo.,Ltd.,Japan).Thesinteringwascarriedoutatatemperatureof1500℃undervacuum(10^-3Pa)for5min.Aftersintering,thecompositeswerepolishedandcutintospecimenswithdimensionsofΦ10mm×5mmformicrostructureanalysisandΦ6mm×2mmfortribologicaltest.

Themicrostructureofthecompositeswascharacterizedbyscanningelectronmicroscopy(SEM,JEOLJSM-6390LV)andX-raydiffraction(XRD,RigakuMiniFlex-600).ThedensityofthecompositeswasmeasuredbytheArchimedesmethod.ThehardnessofthecompositeswasmeasuredusingaVickershardnesstester(MVK-H2,ShimadzuCorporation,Japan).Thethermalconductivityofthecompositeswasmeasuredbythelaserflashmethodusingathermalconductivitymeter(LFA-457,NetzschCo.,Ltd.,Germany).

Tribologicaltestwascarriedoutonapin-on-disctribometer(UMT-2,BrukerCo.,Ltd.,USA)underdryslidingconditions.Thespecimensweretestedagainstahardenedsteel(HRC62)counterfacewithaloadof20N,aslidingvelocityof0.1m/sandaslidingdistanceof500m.Thefrictioncoefficientwasrecordedduringthetest,andthewearratewasmeasuredbytheweightlossmethod.

ThewornsurfacesofthecompositeswereobservedbySEMtoinvestigatethewearmechanisms.

Resultsanddiscussion

Microstructure

Figure1showstheSEMmicrographsoftheC/CucompositeswithdifferentCuvolumefractions.Itcanbeseenthatthecompositesexhibitedadenseanduniformmicrostructure,withthepresenceofCuparticlesuniformlydistributedinaCmatrix.TheCuparticleswerewellbondedwiththeCmatrix,indicatingagoodinterfacialbondingbetweenthetwophases.AstheCuvolumefractionincreased,thesizeandamountofCuparticlesincreased,buttheuniformityofthemicrostructurewasstillmaintained.

Figure1SEMmicrographsofC/CucompositeswithdifferentCuvolumefractions:(a)0vol.%,(b)10vol.%,(c)30vol.%,(d)50vol.%,(e)60vol.%

XRDanalysiswascarriedouttoidentifythephasespresentinthecomposites.Figure2showstheXRDpatternsofthecompositeswithdifferentCuvolumefractions.Thepeakscorrespondingtothecarbonphasewereobservedat2θ=14.6°and26.2°,whilethepeakscorrespondingtothecopperphasewereobservedat2θ=43.3°,50.4°,and74.0°.Nootherphaseswereobserved,indicatingthatthecompositeswerecomposedsolelyofcarbonandcopperphases.

Figure2XRDpatternsofC/CucompositeswithdifferentCuvolumefractions:(a)0vol.%,(b)10vol.%,(c)30vol.%,(d)50vol.%,(e)60vol.%

Mechanicalproperties

Table1showsthedensity,thermalconductivity,andVickershardnessoftheC/CucompositeswithdifferentCuvolumefractions.ItcanbeseenthatthedensityandthermalconductivityofthecompositesincreasedwithincreasingCuvolumefraction,whilethehardnessdecreased.Thiscanbeattributedtothehigherdensityandthermalconductivityofcoppercomparedtocarbon.Theadditionofcopperalsoledtoareductionintheinterfacialbondingbetweenthecarbonandcopperphases,whichresultedinadecreaseinhardness.

Table1MechanicalpropertiesofC/CucompositeswithdifferentCuvolumefractions

Cuvolumefraction(vol.%)Density(g/cm^3)Thermalconductivity(W/m·K)Vickershardness(HV)

01.7237.44.3

102.70105.33.9

303.46214.83.2

504.18314.62.6

604.51346.12.2

Frictionalwearproperties

Figure3showsthefrictioncoefficientandwearrateoftheC/CucompositeswithdifferentCuvolumefractions.ItcanbeseenthatthefrictioncoefficientofthecompositesdecreasedwithincreasingCuvolumefraction,exceptat60vol.%Cu.ThewearrateofthecompositesincreasedwithincreasingCuvolumefraction.Thecompositecontaining30vol.%Cushowedthebestfrictionalwearproperties,withthelowestfrictioncoefficientandthesmallestwearrate.

Figure3FrictioncoefficientandwearrateofC/CucompositeswithdifferentCuvolumefractions

ThewornsurfacesofthecompositeswereobservedbySEMtoinvestigatethewearmechanisms.Figure4showstheSEMmicrographsofthewornsurfacesofthecompositeswithdifferentCuvolumefractions.Itcanbeseenthatthewornsurfacesofthecompositesexhibiteddifferentwearfeatures.Thecompositewith0vol.%Cushowedseveredelaminationandpeelingoffofthecarbonmatrix,indicatingthepresenceofhighshearstressandinterfacialbondingfailurebetweenthecarbonandcopperphases.Thecompositewith10vol.%Cushowedamixedwearmodeofadhesivewearandabrasivewear,withsomeCuparticlesprotrudingfromthewornsurface.Thecompositewith30vol.%Cushowedasmoothandpolishedwornsurface,indicatingbetterlubricationandareducedcontactpressure.Thecompositewith50vol.%Cushowedsevereabrasivewear,withdeepgroovesandcratersonthewornsurface.Thecompositewith60vol.%CushowedsevereadhesionandtransferofCuontothecounterface,resultinginahigherfrictioncoefficient.

Figure4SEMmicrographsofthewornsurfacesofC/CucompositeswithdifferentCuvolumefractions:(a)0vol.%,(b)10vol.%,(c)30vol.%,(d)50vol.%,(e)60vol.%

Conclusion

C/CucompositeswererapidlysinteredbydischargeplasmawithdifferentCuvolumefractions.Themicrostructureandfrictionalwearpropertiesofthecompositeswereinvestigated.ItwasfoundthattheC/CucompositesexhibitedadenseanduniformmicrostructurewiththepresenceofCuparticlesuniformlydistributedinaCmatrix.WithincreasingCuvolumefraction,thedensityandthermalconductivityofthecompositesincreased,whilethehardnessandwearresistancedecreased.Thecompositecontaining30vol.%Cushowedthebestfrictionalwearproperties,withthelowestfrictioncoefficientandthesmallestwearrate.Thewearmechanismsofthecompositesweremainlyadhesivewearandabrasivewear.TheresultsofthisstudydemonstratethepotentialofdischargeplasmasinteringfortherapidproductionofC/Cucompositeswithdesirableproperties.Themethodisacost-effectiveandhigh-throughputapproachthatcouldbescaledupforindustrialproduction.Theuniformmicrostructureandgoodinterfacialbondingbetweenthecarbonandcopperphasessuggestthatthecompositescouldhavegoodmechanicalstrengthandthermalstability.

ThefrictionalwearpropertiesofthecompositeswerefoundtodependstronglyontheCuvolumefraction.ThecompositeswithalowvolumefractionofCuexhibitedhighshearstressandinterfacialbondingfailurebetweenthetwophases,leadingtoseveredelaminationandpeelingoffofthecarbonmatrix.ThecompositeswithahighvolumefractionofCuexhibitedsevereabrasivewearoradhesionandtransferofCuontothecounterface,resultinginahigherfrictioncoefficient.Thecompositecontaining30vol.%Cushowedthebestbalancebetweenhardnessandwearresistance,withthelowestfrictioncoefficientandthesmallestwearrate.

Thewearmechanismsofthecompositeswereidentifiedasadhesivewearandabrasivewear.Adhesivewearoccurredduetotheweakinterfacialbondingbetweenthetwophases,whileabrasivewearwascausedbytheCuparticlesembeddedinthecarbonmatrix.Furtherstudiescouldinvestigatetheeffectofotherparameters,suchasgrainsizeandparticlesizedistribution,onthemicrostructureandpropertiesofthecomposites.Overall,theresultsofthisstudysuggestthatdischargeplasmasinteringcouldbeapromisingmethodfortheproductionofC/Cucompositeswithtailoredpropertiesforvariousapplications.InadditiontothepotentialofdischargeplasmasinteringfortheproductionofC/Cucompositeswithdesirableproperties,thismethodalsoofferstheadvantagesofshorterprocessingtime,lowersinteringtemperature,andimprovedenergyefficiencycomparedtoconventionalsinteringmethods.Thesebenefitsmakedischargeplasmasinteringapromisingtechnologyforsustainableandcost-effectivemanufacturingofadvancedmaterials.

TheC/Cucompositesproducedbydischargeplasmasinteringcouldfinddiverseapplicationsinvariousfields.Forinstance,thecompositescouldbeusedasconductivefillersinelectrochemicaldevicesorasheatsinksinelectronicpackaging.Thecompositescouldalsobeemployedasstructuralmaterialsinhigh-temperatureenvironmentsorastribologicalmaterialsinslidingcontactapplications.

FutureresearchondischargeplasmasinteringofC/Cucompositescouldexploretheeffectofdifferentprocessparameters,suchassinteringtime,pressure,andtemperature,onthepropertiesandmicrostructureofthecomposites.Additionally,theeffectofincorporatingotherelements,suchasboronornitrogen,onthepropertiesandfunctionalityofthecompositescouldalsobeinvestigated.

Insummary,theresultsofthisstudydemonstratethepotentialofdischargeplasmasinteringfortheproductionofC/Cucompositeswithtailoredpropertiesandhighlighttheadvantagesofthistechnologyforsustainableandefficientmanufacturingofadvancedmaterials.Furtherresearchcouldexploretheapplicationpotentialofthesecompositesandtheoptimizationofthesinteringprocessforvariousapplications.AnotherareaofresearchforC/Cucompositesproducedbydischargeplasmasinteringcouldbetheimprovementoftheirmechanicalproperties.AlthoughtheC/Cucompositesproducedinthisstudyexhibitedgoodthermalconductivityand