2-paper-new coating systems for steel strips by physical vap

1、NewCoatingSystemsfSteelStripsbyPhysicalVapDepositionSCHEFFELB.METZNERChr.ROEGNERF.H.FraunhoferInstitutfuerElektronenstrahlundPlasmatechnik(FEP)Winterbergstrasse28D01277DresdenGermanyAbstract:CoatingsdepositedbyPhysicalVa

2、pDeposition(PVD)areapromisingalternativefthecrosionprotectionofstripsteels.Conventionallycoatingsystemshavedeficitsregardingenvironmentalcompatibilitysomeapplicationproperties.PVDisanenvironmentfriendlytechnologyisfamous

3、fthenearlyunlimitedmaterialprocessvariety.ElectronBeamHighrateDeposition(EBHD)withdepositionratesuptosomemicrometerspersecondisoneofthemostpowerfulPVDtechnologiesflowcostcoating.Thecombinationofevapationwithpowerfulplasm

4、aisanefficientpossibilitytoimprovethelayerpropertiesofcompoundshighmeltingmetals.InthepaperanoverviewaboutsuchemergentPVDtechnologieswillbepresented.Thepaperpresentssomeexamplesofnewlayerstacksontosteelsheetsontogalvaniz

5、edsteelsheets.Zincalloycoatingscoatingsofhighmeltingmetalsoxidecoatingsweredepositedinvestigated.Thecoatingswereproducedundertheconditionsofaveryhighdepositionrate(methan100nms)withinaninlinevacuumcoaterfmetallicstripssh

6、eets.Theinfluenceoftheprocessplasmaparametersonthelayerpropertieswasinvestigatedwillbedemonstratedfsomespecialapplications.Keywds:steelstripcrosionprotectionzincmagnesiumPVDvacuumcoating0IntroductionThecoatingofmetalshee

7、tsstripshasdevelopedtoahighlevelwithcrosionprotectionlayersbasedonzinctinplayingaparticularlyimptantrole.Theselayersaremanufacturedmainlybyeitherhotdipcoatingelectrolyticdepositiontherearealargenumberofthesehighproductiv

8、ityplantsinoperationwldwide.Anothertechnologyimptantfthesurfacefinishingofmetallicsheetsstripsistheuseofganiccoatingssuchasvarnishes.Highloadedmetalcomponentse.g.automobilebodiesareprotectedfromcrosionwithamultilayersyst

9、emcombiningvariouscoatingtechnologies.Nowadaysstripsofstartingmaterialarefirstlygalvanizedeitherelectrolyticallybyhotdipcoating.Afurthercoatingthenfollowstoensurethatthezinccoatingistemparilyresistanttocrosionfmsagoodfou

10、ndationfthevarnish.Chromiumphosphatecompoundsaredepositedbydippingsprayingrinsingprocessesfollowedbyacoatingofmultilayeredvarnish.InprinciplePVDprocesses(PhysicalVapDeposition)aresuitablefdepositingcrosionprotectionother

11、functionallayersontometallicsheetsstrips.Thistechnologyofferstwodecidingadvantages:?awidevarietyofcoatingmaterialscanbedeposited(metalsalloyscompoundsalsometastablegradientlayers)?itisenvironmentallyfriendly.1UseofthePVD

12、processThecoatingcoststhequalityofthedepositedlayersfPVDcoatingsmustbecomparedwithotherconventionalsurfacefinishingprocessesparticularlythosethatpermitthecoatingoflargeareasathighspeed.Comparativelylowfinishingcostscanbe

13、achievedwhenthetreatmentwilldeterminethemaximumapplicablesubstratetemperature.Zincexhibitsanelevatedvappressureundervacuumatraisedtemperaturesevapatingatarateofabout30nmsevenat300Cat1.5msat400C[4].Theseeffectswouldbeinto

14、lerableinmanyapplications.Theprincipleofplasmaactivateddepositionhasbeenknownfalongtime[5].Untilthe1990showevertherewerenohighpoweredsourcesfdenseplasmasthatweresuitedtohighcoatingrateslargeareacoating.GermanfirmstheFrau

15、nhoferInstitutfrElektronenstrahlundPlasmatechnikdevotedthemselvestothetaskofdevelopingsuchsources.Themosteffectiveplasmasaregeneratedbyarcdisge.AtFEPsomeprocessesweredevelopedonthebasisofcombiningEBHDwithdifferentcontrol

16、ledarcdisges.IntheSADprocess(SpotlessarcActivatedDeposition)theEBHDiscombinedwithaspecialvacuumarcdisge.Aspotlesscathodicarcisburningonthehotevapatingareasheatedbytheelectronbeam.Thisspecialkindofarcdisgeisfmedduringevap

17、ationofedmetalsespeciallytherefractymetals.Thespotlessarcisacterizedbyarelativelylowcathodiccurrentdensityintherangeof10…100Acm.Thisdiffusearcrootoccupiesanareaofsomecmdoesnotemitanylets.Bydeflectionoftheelectronbeamapla

18、smaactivatedlargeareaevapationcanberealizedwithouthighadditionalexpenditure.Witharccurrentsofmanythousampsitispossibletoachieve(e.g.fdepositionwithtitaniumatarateof1ms)ioncurrentdensitiesupto400mAcmatthesubstrate[6].Thec

19、ombinationofEBHDwithahollowcathodearcdisgefmsthebasisoftheHADprocess(HollowcathodearcActivatedDeposition)[7].Flargeareaevapationsomehollowcathodesareinstalledsidebysidedirectlyunderthesubstratetheirdisgesperatethevapclou

20、d.ThisprocessisparticularlysuitablefreactivedepositionwithinsulatingcompoundssuchassiliconAluminiumoxides.Afeatureofhollowcathodearcdisgeisthedirectedpartoftheelectronsintheplasma.Theseelectronshaveanaverageenergyof1015e

21、V.Acrespondinglyhighselfbiasvoltageatinsulatingsubstratesresultsfromthehighelectrontemperatureintheplasma.Aspecialarrangementoftheelectrodesallowsthelongtermfaultlessdepositionofhighlyinsulatingmaterials.Typicaldisgecurr

22、entsareofthederof200Aperhollowcathode.WiththistypeofarrangementAl2O3layerscanbedepositedatratesof50120nmsioncurrentdensitiesof3050mAcmatthesubstrate.3edresultsfromnewcoatingsystemsfmetallicsheetsstripsInrecentyearsmanyin

23、novativecoatingsystemsusingEBHDdepositiononmetallicsheetsstripshavebeenbasedonthenewPVDprocesses.Atthefefrontarethoseplasmaactivatedprocesses(SADHAD)developedatFEPfimprovingthecoatingmicrostructure.Asexpectedtheinfluence

24、oftheplasmaonthemicrostructureofthecoatedlayersisobservedfbothprocesses.InFig.2theeffectoftheSADprocessduringEBHDonthecoatingofchromiumlayersisshowninscanningelectronmicroscopeimagesofthecrosssections.Figure2ashowsa4mthi

25、ckchromiumlayerdepositedwithoutplasmaactivationatarateof1ms.Thecoatinghasapousmicrostructurewithcolumnsthelayersurfaceisrough.HoweverFig.2bshowsthattheinfluenceofthediffusearcdisgeintheSADprocesscombinedwithabiasvoltageo

26、f100Vresultsinthechromiumlayerhavingadensermicrostructuresmoothersurface.Theeffectcanalsobedemonstratedincrosiontestswithincreasedresistancetocrosionfthesamelayerthickness.Previouslysuchdenselayerscouldonlybemanufactured