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ContentslistsavailableatScienceDirect
Optik
journalhomepage:www.elsevier.de/ijleo
1Analysisonthephysicalmechanismoflasercladdingcrackandits2
in?uencefactors3Q1
FuxingFu?,YanliZhang,GengrongChang,JunDai4DepartmentofOptoelectronicScienceandPhysics,Xi’anUniversity,Xi’an710065,China5
618articleinfoabstract78Articlehistory:Thephysicalmechanismofcrackformationintheprocessoflasercladdinghasbeenanalysedbytheoret-9Received22December2014icalderivation,andthein?uencefactorshavebeendiscussedindetail.ThepowderofNi60wascladded10Accepted10October2015onthesurfaceofbasematerial(40Cr)byexperiment,andthecharacteristicsofcrackshavebeenanalysed11Availableonlinexxxbyobservingthedistributionsofcrackswithopticalmicroscope.Theresultsoftheoryandexperiments1213Keywords:showthatthecrackratiooflasercladdinglayerisin?uencedbylaserpower,spotdiameterandscanning14Laserspeed,whichisproportionaltothepoweroflaser,andinverselyproportionaltoscanningspeedandthecladding15Claddingdiameterofspot.crack16Energy?2015PublishedbyElsevierGmbH.density17
Spotdiameter19
1.Introductionthein?uenceoflaserscanningspeedtocladdingcrack.Sofar,thephysicalmechanismofcladdingcrackandtherelationofcladding20
Inthetechnologiesofmaterialsurfacemodi?cation,lasercrackwiththelaserpower,spotdiameterandscanningspeedare21
claddingisaveryeffectivemethod,whichcansigni?cantlyimprovestillnotclearandde?nite.Therefore,itissigni?cativetoresearch22
thepropertiesofmaterialsurface,suchaswear-resisting,anti-thephysicalmechanismoflasercladdingcrackanditsin?uence23
corrosion,heat-resistingandantioxidant[1,2].Inaddition,thefactors.24
technologyoflasercladdingcanalsorepairthedamagedproducts,Inthispaper,thephysicalmechanismoflasercladdingcrackhas25especiallycomplexmetalparts[3].So,thistechnologyhasbeenbeenanalysedwithadetailedtheoreticalderivation,andthein?u-26widelyappliedinaerospace,automobilemachine,heavymachin-encefactorsofformationofcrackshavebeendiscussed.Inorderto27eryandsoon.Buttherearesomedefectssuchascladdingcrack,verifythetheoreticalresults,theexperimentoflasercladdingwith28whichisaffectingthequalityandlongevityoftheproduct.UptoNi-Cralloyhasbeencompleted,andtheresultsofexperimenthave29now,theproblemhasnotbeensolvedeffectively.Thestudiesshowbeengivenandanalysed.30thatintheprocessoflasercladding,iftheselectionofcladding31materialisimproperorthetechnologicalparameterisunmatched,2.Thephysicalmechanismofcrackproducing32thecracksareeasilyformedonthesurfaceandintheinteriorof33claddinglayer.ThebasicreasonofcrackformingisthethermalLasercladdingisaprocessofquicklyheatingandquicklycool-34stresswithinthecladdinglayer,becausetheprocessofmaterial’sing,whichcanleadtoformthemicrocracks.Whenlaserbeam35melting,solidi?cationandcoolingiscompletedunderthecondi-withhighpowerisirradiatedonthesurfaceofmetalmaterial,36tionofextremelyfast,itispronetoproducethethermalstress,iftheenergyoflaserwillbeabsorbedbymetallicsandconverted37thethermalstressexceedsthestrengthlimitofmaterial,thecracktothermalenergy.Inashorttime,thethermalenergydoesnot38Q4isformed[4,5].Aboutthein?uencefactorsofcracking,Gangxiantransfertothedepthsofthematerialsurfacesothatmostofthe39etal.proposedthattheincreaseofthelaserpowerandthereduc-thermalenergyisconcentratedonthesurfaceofthecladding40tionofthefeedratecouldreducethecracking[6];Dongshenetal.regionandformingthethermalstress.Whenthethermalstress41researchedtherelationoflaserpowertocladdingcrack,andpro-exceedsthestrengthlimitofmaterial,thecracksareformed.In42posedthatthecrackcouldbereducedandcontrolledbyusingtheaddition,whenthelaserbeamgoesawayfromthescanningarea,43convexspot[7];Siyuetal.[8]andQinlongetal.[9]researchedthecladdinglayercoolsrapidly,andtherestraintstresswillbeformedquicklybecauseoftherestraintfromthesurroundingcoolerbasematerial;iftherestraintstressisgreaterthanthelimitofQ2
?Correspondingmaterial,themicrocrackswillappearonthesurfaceofcladdingauthor.Tel.:+8602988258851.E-mailaddress:tianlong789@tom.com(F.Fu).layer.http://dx.doi.org/10.1016/j.ijleo.2015.10.0430030-4026/?2015PublishedbyElsevierGmbH.
Pleasecitethisarticleinpressas:F.Fu,etal.,Analysisonthephysicalmechanismoflasercladdingcrackanditsin?uencefactors,Optik-Int.J.LightElectronOpt.(2015),http://dx.doi.org/10.1016/j.ijleo.2015.10.043
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Table1
Theprocessparametersofexperiments.
Waistdiameteroflaser(mm)
Focaldistance(mm)
Rateofpowderfeeding(r/min)
Scanningspeed(mm/s)
Overlaprate
4
111
80
25
50%
72Tracingthesource,thegenerationofcladdingcracksisdeter-73minedbythethermalstressinthecladdinglayer.Assumethatthe74modeoflasersourceisfundamental-modeGaussianbeam,andthe75weldpoolisaspherewithradiusr.Thethermalstress????along76
thedirectionofradiuscanbeexpressedas[10]
√
2??
??
77
????1??
r
=
?E
1r2dr?
???
r3gradtt0
0
3
(1)
78where?istheexpansioncoef?cientofmetalmaterial,Eisthe79elasticmodulusofthematerial,??isPoisson’sratio,t0isthetem-80peratureofcladdinginthecentreofsphere,andgradtisthe81temperaturegradientalongthedirectionofradius,whichcanbe82
expressedas
83
gradt=
??t??r(2)
84
Eq.(1)showsthatthethermalstress????isdeterminedbyE,
85and?,and??theenergydensityoflaser.Whenthe?andE??fthe86claddinglayerareclosetothoseofthebasematerial,thevalueof87Q5????canbecontrolledtoverysmall.So,inordertoinhibitorreduceFig.1.Thedistributionofsurfacecrack.(a)P=1000W;(b)P=1000W;(c)
88theP=1000W;(d)P=1000W.
claddingcracks,thevaluesofE,?and??shouldbeselected89reasonably.
Table2Thecharacteristicsofcladdingcrackwithdifferencepower.90
3.Thein?uencefactorsofthecracksLaserpower(W)Crackingrate(N/mm)CrackdepthCrackwidth91Fromtheviewsofmaterial,theexpansioncoef?cient,elastic10000.20ShallowerWider92modulus12000.16ShallowWideandPoisson’sratioallaffectthegenerationofcracks,but93in15000.15DeepThinapplications,wepaymoreattentiontotheprocessparameters94such18000.11DeeperThinneraslaserpower,spotsize,scanningspeedandfeedrate.Inorder95tocleartherelationshipamongtheprocessparameters,theenergy96
densityoflaserbeamEsisgivenasfollows[11]4.Experimentalresults97
Es=
P
DV(3)b
Theexperimentsoflasercladdinghavebeencompleted,40Cr98wherePisthepoweroflaser,Disthediameterofspot,andVwastakenasthebasematerial,Ni60ascladdingpowder,andbis99theNd:YAGlaserasthermalresource.scanningspeedoflaser.100AccordingtoEq.(3),whenkeepingthevaluesofDandVb101unchanged,thevalueofEsincreaseswiththeincreasingofP,the4.1.Therelationoflaserpowerandcracks102depthofcladdinglayerincreases,andthenumberofairporeinthe103claddinglayerwilldecreasegraduallyorevenbeeliminated,sotheTheprocessparameterswereselectedasshowninTable1.Inthe104numberofthecrackswillalsoreducegradually;whenkeepingtheprocessofexperiments,keepingthevaluesofDandVbunchanged,105valuesofPandVbunchanged,theEsdecreaseswiththeincreasingthepoweroflaserwas1000W,1200W,1500W,and1800W,106ofD,resultinginthenumberofthecracksincreasing,butontherespectively.Theeffectoflasercladdingcanbeobservedbythe107otherhand,thedilutionrateofthecladdinglayerwilldecreaseopticalelectronmicroscope,andthecrackdistributionofcladding108gradually,andthehardnessofthecladdinglayerwillincrease,layerisshowninFig.1.109whichcanimprovethequalityofthesurface.Eq.(3)showsthatTakingthesamecladdingarea,thecharacteristicsofcladding110underthesamecladdingarea,thenumberofthecracksispropor-crackwithdifferencepoweraregiveninTable2.AccordingtoFig.1111tionaltothepoweroflaser,andinverselyproportionaltoscanningandTable2,whenotherparameterskeepunchanged,thecracking112speedandthediameterofspot.Therefore,inordertoreducetheratedecreasesgraduallywiththeincreaseoflaserpower,thedepth113crackingratioandobtainthebestcladdingquality,thesuitableofcrackisdeeperanddeeper,andthewidthofcrackisthinnerand114
processparametersshouldbeselected.thinner.Theresultsagreewiththetheoreticalresults.Table3
Theprocessparametersofexperiments.Laserpower(W)
Waistdiameter(mm)
Focaldistance(mm)
Rateofpowderfeeding(r/min)
Scanningspeed(mm/s)
Overlaprate
1600
4
111
80
20
50%
Pleasecitethisarticleinpressas:F.Fu,etal.,Analysisonthephysicalmechanismoflasercladdingcrackanditsin?uencefactors,Optik-Int.J.LightElectronOpt.(2015),http://dx.doi.org/10.1016/j.ijleo.2015.10.043
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in?uencefactorsofformationofcrackshavebeendiscussed,andtheexperimentsoflasercladdingwithdifferentpowerandspotdiameterhavebeencompleted.Theresearchresultsareasfollows:
(1)Lasercladdingisaprocessofquicklyheatingandquicklycool-ing,andbothheatingandcoolingcouldleadtocrack.Thebasicreasonofformationofcracksisthethermalstress.
(2)Thekeyfactorsofformationofcracksarelaserpower,spot
diameterandscanningspeed.Whenotherparameterskeepunchanged,thecrackingratedecreasesgraduallywiththeincreaseoflaserpower,andincreasesgraduallywiththeincreaseoftheoff-focusdistance.
(3)Lasercladdingisacomplexprocess;inordertoreducethe
crackingratioandobtainthebestcladdingquality,thesuitableprocessparametersshouldbeselected.
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AcknowledgmentsTheworkwassupportedbythefundofXi’anScienceandQ6TechnologyPlanprojects(CXY1352WL02),andtheEducationDepartmentofShaanxiProvincialGovernmentScienti?cResearchPlanproject(14JK2122,14JK2138).
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Fig.2.Thedistributionofsurfacecrack.(a)L=0mm;(b)L=1mm;(c)L=2mm;(d)L=4mm.Table4Thecharacteristicsofcladdingcrackwithdifferenceoff-focusdistance.Off-focusdistance(mm)Rateofcrackgrowth(N/mm)CrackdepthCrackwidthReferences[1]K.Nagarathnam,K.Komvopoulos,Microstructuralanalysisandoxidation
behavioroflaser-processedFe–Cr–Al–Yalloycoatings,Metall.Mater.Trans.A27(1996)381–390.[2]Z.Xiaoyan,W.Xinwei,T.Zengyi,etal.,Abrasivewearresistanceanalysesof
lasercladNi–WCceramic-metalcompositecoatings,ActaMetall.Sin.33(1997)885–890.
[3]Z.Jian,W.Wenni,Z.Longzhi,Researchprogressanddevelopmenttrendoflaser
cladding,HotWork.Technol.42(2013)131–135.
[4]Z.Minlin,L.Wenjin,R.Jialie,Thecriticalin?uencefactorsoncrackformationQ7
duringhighpowerCO2lasercladdingofNiCrSiBalloybypowderfeeding,LaserAppl.20(2000)25–30.
[5]A.Techel,L.M.Berger,S.Nowotny,MicrostructureofadvancedTiC-based
coatingspreparedbylasercladding,J.Therm.SprayTechnol.16(2007)374–380.
[6]Z.Gangxian,Z.Anfeng,L.Dichen,Effectofprocessparameters
onsurfacesmoothnessinlasercladding,Chin.J.Lasers37(2010)296–301.
[7]W.Dongsheng,T.Zongjun,W.Jingwen,etal.,Amethodofcrackcontrolinlaser
claddingprocesswithchangingpowerdensitydistributionoflaserbeam,Chin.J.Lasers38(2011)0103004.
[8]Z.Siyu,Z.Kequan,L.Zheng,In?uenceofscanningspeedsonmicrostruc-tureandpropertiesoflasercladdingWC–B4C–Co,Chin.J.Lasers20(1993)940–943.
[9]L.Qinglong,W.Yanfang,L.Li,etal.,Effectsofscanningspeedonmicrostructures
andpropertiesoflasercladdingFe-basedamorphouscompositecoatings,Chin.J.Lasers40(2013)0603001.
[10]L.Weite,H.Baohai,B.Zhongbo,TheoryAnalysisandApplicationoftheTher-modynamics,ChinaElectricPowerPress,2004.
[11]Z.Xiaobin,Y.Dengke,G.Jianjun,Researchoncrackingoflasercladding,Laser
J.31(2010)44–45.
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01240.10.150.180.23DeeperDeeperShallowShallowerThinnerThinWideWider132
4.2.Therelationoflaserpowerandspotdiameter133134135136137138139140141142143144
Intheexperiments,theprocessparametersareshowninTable3.ThediameterDoflaserspotcanbereplacedbytheoff-focusdistanceLwhichisthelengthfrombasematerialtothefocalplane.KeepingthevaluesofPandVbunchanged,onlychangingthevalueofL,theeffectsofcladdingwithdifferentspotdiameterareshowninFig.2.Thecharacteristicsofcladdingcrackwithdifferenceoff-focusdistancearegiveninTable4.AccordingtoFig.2andTable4,whenotherparameterskeepunchanged,thecrackingrateincreasesgraduallywiththeincreaseoftheoff-focusdistance,thedepthofcrackismoreandmoreshallow,andthewidthofcrackgrowswidergradually,whichissameasthetheoreticalresults.145
5.Conclusions146
Inthispaper,thephysicalmechanismoflasercladdingcrackhasbeenanalysedwithadetailedtheoreticalderivation,thePleasecitethisarticleinpressas:F.Fu,etal.,Analysisonthephysicalmechanismoflasercladdingcrackanditsin?uencefactors,Optik-Int.J.LightElectronOpt.(2015),http://dx.doi.org/10.1016/j.ijleo.2015.10.043