SialonSi3N4系梯度纳米复合陶瓷刀具的切削性能.docx
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SialonSi3N4系梯度纳米复合陶瓷刀具的切削性能
CuttingperformanceofSialon-Si3N4gradednano-composite
ceramiccuttingtools
#
ZHENGGuangming,ZHAOJun,GAOZhongjun,ZHOUYonghui
**
5（KeyLaboratoryofHighEfficiencyandCleanMechanicalManufactureofMOE,Schoolof
MechanicalEngineering,ShandongUniversity,JiNan250061）
Foundations:
theSpecializedResearchFundfortheDoctoralProgramofHigherEducation（No.
20090131110030）,theNationalBasicResearchProgramofChina（No.2009CB724402）,theNationalNatural
ScienceFoundationofChina（No.50875156）
Briefauthorintroduction:
ZHENGGuangming,（1986–）,Male,Postgraduatestudentfordoctordegree,Research
onhigheffciencycuttingandtoolmaterials
Correspondanceauthor:
ZHAOJun,（1967–）,Mail,Ph.D.,Professor.Researchonhigheffciencycuttingand
toolmaterials.E-mail:
zhaojun@
Abstract:
Sialon-Si3N4gradednano-compositeceramictoolmaterialswerefabricatedbyusing
hot-pressingtechnique.Thecuttingperformanceofthegradedtoolswereinvestigatedviaturningof
Inconel718alloyincomparisonwithcommonreferencetools.Theresultsshowedthatgraded
10structureinSialon-Si3N4gradedceramictoolmaterialscaninduceresidualcompressivestressesinthe
surfacelayerduringfabrication.Toollifetimeofgradedceramictoolwashigherthanthatofthe
commonreferencetool.Thelongertoollifeofthegradednano-compositeceramictoolwasattributed
toitssynergisticstrengtheningandtougheningmechanismsinducedbytheoptimumgraded
compositionalstructureofthetoolandtheadditionofnano-sizedparticles.Wearmechanisms
15identifiedinthemachiningtestsinvolvedadhesivewearandabrasivewear.Themechanisms
responsibleforthehighertoollifeweredeterminedtobetheformationofcompressiveresidualstress
inthesurfacelayerofthegradedtools,whichledtoanincreaseinresistancetofracture.
Keywords:
Gradedceramiccuttingtools;Wearmechanisms;Residualstress;Inconel718
200Introduction
Si3N4ceramicsandSialonceramicsareconsideredtobetheidealtoolmaterialsfor
machiningofNickel-basedsuperalloysathigherspeedconditionsbecauseoftheirrelativelyhigh
strengthandfracturetoughness
[1,2]
.Whereas,thecharacteristicsofSi3N4andSialonceramic
limitingtheirapplicationsaretheirrelativelylowerhardnessandwearresistance
[3,4]
.
25Conventionally,Si3N4-basedandSialon-basedceramictoolmaterialswerestrengthenedand
toughenedbytheadditionofparticleslikeSiC,TiCN,TiC,etc.toimprovethemechanical
properties
[5-7]
.Thematrixgrainsofthecompositewerealsorefinedbyaddingnano-Si3N4
particles,becausetheadditionofnano-Si3N4particlescouldpromotetheformationoftheduplex
distributioncharacteristic.Theoptimumflexuralstrengthandfracturetoughnesswereobtained
whenthevolumefractionratioofnano-sizedSi3N4tomicro-sizedSi3N4isfixedat1:
3
[8]
30.In
addition,Theintroductionoftheconceptoffunctionallygradedmaterial（FGM）intothe
fabricationofceramiccuttingtoolmaterialsprovidedanewapproachtoimprovetheirthermal
andmechanicalproperties
[9]
.Functionallygradedcuttingceramicswithsymmetricalstructure
havebeendevelopedtoperformhighspeedintermittentmachiningofhardmetals,withhigher
toollivesthanthoseofhomogeneouscuttingceramics
[10]
35.
Theunderstandingofthewearmechanismsincuttingprocessesistheprerequisitefornot
onlytheproperapplicationbutalsothedevelopmentofgradedceramictoolmaterials.Inturning
ofInconel718,thetypicalweartypesofceramictoolsarecraterwear,flankwearanddepthofcut
notchwearwhicharesometimeaccompaniedbychipping
[11-13]
.Thetypicalwearmechanismsof
40ceramictoolsinturningofInconel718areadhesivewear,abrasivewear,plasticdeformation,
diffusionwearandmicro-breakout
[1,11,14]
.Thewearmechanismsvarywiththelocationofworn
area.Forexample,adhesivewearisthemainwearmechanismsintherakeface,whileabrasive
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中国科技论文在线
wearisthemainwearmechanismsintheflankface.Thecharacteristicofthedepthofcutnotch
wearisveryseverewhenmachiningInconel718withceramictools
[2,15]
.Additionally,the
45diffusionelementsofInconel718alloytothetoolrakefacesuchasNiandComightaccelerate
thetoolwearrate
[11]
.
Inthepresentpaper,Sialon-Si3N4gradednano-compositeceramictoolmaterialswere
fabricatedbytheoptimumgradedcompositionalstructureofthetoolandtheadditionof
nano-sizedparticles.Thecuttingperformanceandwearmechanismsofgradedceramictoolswere
50investigatedviaturningofInconel718,withcommonreferencetoolsusedascompetitors.Worn
surfacesofthetoolswerecharacterizedbyscanningelectronmicroscopy（SEM）andenergy
dispersiveX-rayspectroscopy（EDS）torevealthewearmechanisms.Surfaceroughnessofthe
finishhardturningofInconel718andmicrostructuresofthechipswerealsoanalyzed.
1Experimentalmethods
55ThedesignandfabricationofSialon–Si3N4gradednano-compositeceramictoolmaterials
wasdiscussedinourpreviousstudy
[16]
.Inthepresentstudy,Sialon-Si3N4gradednano-composite
ceramictoolmaterialswerefabricatedbytheoptimumgradedcompositionalstructureofthetool
andtheadditionofnano-sizedparticles.Thegradedmaterialshaveafive-layeredwith
symmetricalstructure.GSS1（theouterlayerandtheinnerlayerwereSi3N4-basedmaterial）was
60sinteredwiththethicknessratioof0.3at1700℃for60minunderafixeduniaxialpressureof
35MPa.GSS2（theouterlayerwasSialon-basedmaterialandtheinnerlayerwasSi3N4-based
material）wassinteredwiththethicknessratioof0.3at1750℃for60minunderafixeduniaxial
pressureof35MPa.Forthepurposeofcomparison,homogeneousreferenceceramicmaterials
SAAT10（Sialon-basedmaterial）andST10（Si3N4-basedmaterial）werealsomanufacturedby
65hot-pressing.
ThecuttingperformanceoftheSialon-Si3N4gradednano-compositeceramictools（GSS1
andGSS2）weretestedincomparisonwiththatofthereferenceceramictools（SAAT10andST10）
andacommerciallyavailableSialonceramictool（Kennametal,typeisSNGN120408T01020,
gradeisKY1540）.ThemechanicalpropertiesofthefivetoolmaterialsarelistedinTable1.The
70toolshavethefollowinggeometryparameters:
rakeangleγ0=-5°,clearanceangleα0=5°,
inclinationangleλs=0°,sidecuttingedgeangleκr=45°.
Tab.1Averagesandstandarddeviationsofmechanicalpropertiesofthetoolmaterials.
Toolsσf
/MPaKIC/MPa·m1/2HV/GPa
GSS1980±609.54±0.52
a
16.91±0.30
a
GSS2810±309.33±0.46
a
16.98±0.24
a
ST10860±908.19±0.9116.29±0.23
SAAT10645±957.80±0.5516.59±0.31
KY15407.45±0.6118.24±0.25
Note:
a
thepropertyofthesurfacelay
75
Acomputernumericallycontrolled（CNC）centrelathePUMA200MAwithmaximumspeed
of6000r/minwasusedforthemachiningtrials.Machiningtrialswereconductedusing120mm
diameter×380mmlongInconel718alloybars.Alltestswerecarriedoutwiththefollowing
parameters:
depthofcutap=0.1mm,feedratef=0.1mm/rev,cuttingspeedv=80,120and200
80m/min.
AverageflankwearVBave=0.30mmwasusedasthetoollifecriterion.Theconditionofthe
cuttingedgewasexaminedperiodically,andanyapparentchangeintheedgesurfacewasclosely
examinedwithanopticalmicroscope.Ascanningelectronmicroscope（SEM）（JSM-6380LA,
Japan）equippedwithanenergy-dispersiveX-rayspectrometer（EDS）wasusedtoexaminethe
-3-
中国科技论文在线
85natureoftheworntoolsandobservemorphologicalfeaturesofchips.Thesurfaceroughnessof
theInconel718wasmeasuredbyaportablesurfaceroughnesstester（ModelTR200,China）.The
surfaceroughnessmeasuresusedinthepaperisthearithmeticmeanvalueofthesurface
roughnessofprofile,Ra.
2Resultsanddiscussion
902.1CuttingperformanceofSialon-Si3N4gradednano-compositeceramictools
Fig.1Averageflankwearcurvesofthefivetoolsatf=0.1mm/randap=0.1mm,
（a）v=80m/min,（b）v=120m/min,（c）v=200m/min.
95
Fig.1showsthevariationofaverageflankwearwidthwithcuttingtimeofthefivetoolsin
turningofInconel718,testedatdifferentspeedswith0.1mm/rfeedrateand0.1mmdepthofcut.
AscanbeseenfromFig.1a-c,amongthefivecuttingtools,gradednano-compositeceramictools
（GSS1andGSS2）showedbetterperformancethanthatofhomogeneousreferencetools（ST10
100andSAAT10）,especiallyatlowercuttingspeeds80m/minand120m/min.Furthermore,the
gradedceramictoolGSS1showedbettercuttingperformancethanthatofthecommercially
availableSialonceramictoolKY1540atlowercuttingspeeds80and120m/min.Thetoollifeof
SAATwastheshortestbecauseofitsrelativelylowflexuralstrengthandfracturetoughness（see
Table1）.
105Fromthecuttingexperiments,theresultshaveshownthattoollifewasaffectedbycutting
speedssignificantly.Itwasfoundthattheceramictoolexhibitedarelativelongcuttinglifeat
cuttingspeed120m/minunderthisexperimentconditions.AscanbeseenfromFig.1a,the
ceramictoolswerenotsuitableforlowspeedcuttingofnickel-basedalloysbecauseoftheshorter
toollifeofthefivetoolsatcuttingspeed80m/min,atleastinthisexperimentconditions.
110Increasingincuttingspeedcausedalagerincrementincuttingtemperatureatthecuttingedgeof
thetools.Thehighertemperaturecausedthetoolstolosetheirstrength.Therefore,thetoolslives
wereshortestatcuttingspeed
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