1、DRAFT FOR DEVELOPMENT DD ENV 12923-2:2001 Advanced technical ceramics Monolithic ceramics Part 2: Oxidation test ICS 81.060.30 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWDD ENV 12923-2:2001 This Draft for Development, having been prepared under the direction of the Sector
2、Committee for Materials and Chemicals, was published under the authority of the Standards Committee and comes into effect on 15 September 2001 BSI 07-2001 ISBN 0 580 38295 8 National foreword This Draft for Development is the English language version of ENV 12923-2:2001. This publication is not to b
3、e regarded as a British Standard. It is being issued in the Draft for Development series of publications and is of a provisional nature because it is considered that further experience is required in its application before it is converted into a European and hence British Standard. It should be appl
4、ied on this provisional basis, so that information and experience of its practical application may be obtained. Comments arising from the use if this Draft for Development are requested so that UK experience can be reported to the European organization responsible for its conversion into a European
5、Standard. A review of this publication will be initiated 2 years after its publication by the European organization so that a decision can be taken on its status at the end of its three-year life. The commencement of the review period will be notified by an announcement in Update Standards. Accordin
6、g to the replies received by the end of the review period, the responsible BSI Committee will decide whether to support the conversion into a European Standard, to extend the life of the prestandard or to withdraw it. Comments should be sent in writing to the Secretary of BSI Technical Committee RPI
7、/13, Advanced technical ceramics, at 389 Chiswick High Road, London W4 4AL, giving the document reference and clause number and proposing, where possible, an appropriate revision of the text. A list of organizations represented on this committee can be obtained on request to its secretary. Cross-ref
8、erences The British Standards which implement international or European publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Cat
9、alogue. Summary of pages This document comprises a front cover, an inside front cover, the ENV title page, pages 2 to 18, an inside back cover and a back cover. The BSI copyright date displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No.
10、 Date CommentsEUROPEANPRESTANDARD PRNORMEEUROPENNE EUROPISCHEVORNORM ENV129232 July2001 ICS81.060.30 Englishversion AdvancedtechnicalceramicsMonolithicceramicsPart2: Oxidationtest CramiquestechniquesavancesCramiques monolithiquesPartie2:Dterminationdeloxidation HochleistungskeramikMonolithischeKeram
11、ikTeil2: Oxidationsprfung ThisEuropeanPrestandard(ENV)wasapprovedbyCENon4June2001asaprospectivestandardforprovisionalapplication. TheperiodofvalidityofthisENVislimitedinitiallytothreeyears.AftertwoyearsthemembersofCENwillberequestedto submittheir comments,particularlyonthequestionwhethertheENVcanbec
12、onvertedintoaEuropeanStandard. CENmembersarerequiredtoannouncetheexistenceofthisENVinthesamewayasforanENandtomaketheENVavailablepromp tly atnationallevelinanappropriateform.Itispermissibletokeepconflictingnationalstandardsinforce(inparalleltothe ENV)untilthefinal decisionaboutthepossibleconversionof
13、theENVintoanENisreached. CENmembersarethenationalstandardsbodiesofAustria,Belgium,CzechRepublic,Denmark,Finland,France,Germany,Greece, Iceland,Ireland,Italy,Luxembourg,Netherlands,Norway,Portugal,Spain,Sweden,SwitzerlandandUnitedKingdom. EUROPEANCOMMITTEEFORSTANDARDIZATION COMITEUROPENDENORMALISATIO
14、N EUROPISCHESKOMITEEFRNORMUNG ManagementCentre:ruedeStassart,36B1050Brussels 2001CEN Allrightsofexploitationinanyformandbyanymeansreserved worldwideforCENnationalMembers. Ref.No.ENV129232:2001EENV129232:2001(E) 2 Contents page Foreword . 3 1S C O P E4 2 NORMATIVEREFERENCES4 3 TERMSANDDEFINITIONS5 4
15、BACKGROUND5 5 INTERFERENCES6 6 APPARATUS . 8 7 TESTPIECES10 8 TESTPROCEDURE11 9 EXPRESSIONOFRESULTS13 10 REPORT . 14 AnnexA(informative)Interlaboratoryevaluationofthetestprocedure16 Bibliography . 18ENV129232:2001(E) 3 Foreword ThisEuropeanPrestandardhasbeenpreparedbyTechnicalCommitteeCEN/TC184 “Adv
16、ancedtechnicalceramics“,thesecretariatofwhichisheldbyBSI. EN12923consistsoftwoparts: Part1: Generalpracticeforundertakingcorrosiontests(ENV) Part2: Oxidationtest (ENV) AnnexAisinformative. ThisPrestandardincludesaBibliography. AccordingtotheCEN/CENELECInternalRegulations,thenationalstandardsorganiza
17、tions ofthefollowingcountriesareboundtoannouncethisEuropeanPrestandard:Austria, Belgium,CzechRepublic,Denmark,Finland,France,Germany,Greece,Iceland,Ireland, Italy,Luxembourg,Netherlands,Norway,Portugal,Spain,Sweden,Switzerlandandthe UnitedKingdom.ENV129232:2001(E) 4 1S C O P E ThisPartofENV12923desc
18、ribesasimpleoxidationtestforadvancedtechnicalceramics. Thetestisdesignedtogiveanassessmentofthemassanddimensionalchangesoftestpieces followingoxidationathightemperatureinanoxidizingatmosphere,andtoassesswhether oxidationhasasignificanteffectonthesubsequentstrength,eitheratroomtemperatureorat elevate
19、dtemperatures. NOTE1Thistestmethoddoesnotallowdefinitionofothermechanicalperformancechanges resultingfromhightemperatureexposure,suchaschangesinsusceptibilitytosubcriticalcrack growth,creepbehaviour,migrationofsecondaryconstituents,etc. NOTE2Thistestmethoddoesnotcovertheadditionaleffectsofothercorro
20、dentsintheambient atmosphere,suchassaltvapours,reducingorcorrosivegases,andothercontaminants.Thismethod alsodoesnotcovertestsatpressuresotherthanambientatmosphericpressure. NOTE3Aninterlaboratoryevaluationoftheproceduregiveninthisstandardissummarisedinannex A. 2 NORMATIVEREFERENCES ThisEuropeanPrest
21、andardincorporatesbydatedorundatedreference,provisionsfromother publications.Thesenormativereferencesarecitedattheappropriateplacesinthetextandthe publicationsarelistedhereafter.Fordatedreferences,subsequentamendmentstoorrevisions ofanyofthesepublicationsapplytothisEuropeanPrestandardonlywhenincorpo
22、ratedinit byamendmentorrevision.Forundatedreferences,thelatesteditionofthepublication referredtoapplies(includingamendments). ENV8201 AdvancedtechnicalceramicsMonolithicceramicsThermomechanical propertiesPart1:Determinationofflexuralstrengthatelevated temperature. EN8431 AdvancedtechnicalceramicsMon
23、olithicceramicsMechanicalproperties atroomtemperaturePart1:Determinationofflexuralstrength. ENV1006 AdvancedtechnicalceramicsMethodsoftestingmonolithicceramics Guidanceonthesamplingandselectionoftestpieces. EN605841 ThermocouplesPart1:Referencetables(IEC605841:1995). EN605842 ThermocouplesPart2:Tole
24、rances(IEC605842:1982+A1:1989). ENISO/IEC17025 Generalrequirementsforthecompetenceoftestingandcalibration laboratories(ISO/IEC17025:1999). ISO3611 Micrometercallipersforexternalmeasurement. ISO46771 AtmospheresforconditioningandtestingDeterminationofrelativehumidity Part1:Aspiratedpsychrometermethod
25、.ENV129232:2001(E) 5 ISO46772 AtmospheresforconditioningandtestingDeterminationofrelativehumidity Part2:Whirlingpsychrometermethod. ISO6906 Verniercallipersreadingto0.02mm. 3 TERMSANDDEFINITIONS ForthepurposesofthisEuropeanPrestandardthefollowingtermsanddefinitionsapply. 3.1 oxidation processofreact
26、ionofaceramicmaterialwithoxygeninthesurroundingatmosphere, includinganyinternalreactionsasaresultofthepresenceofopenporosityorofdiffusionof ionstoorfromtheceramicsurface 3.2 catastrophicoxidation oxidationofaceramicmaterialwhich,underprescribedconditionsleadstorapidmaterial destructionasaresultoflac
27、kofdevelopmentofprotectivesurfacelayers,skinsorscales 4 BACKGROUND Nonoxideceramicmaterials,suchasthosebasedonsiliconnitride,siliconcarbide,titanium diborideandboronnitride,aresubjecttochemicalchangewhenexposedtooxygenin ambientatmospheresathightemperatures.Thechangesaregenerallythesubstitutionofthe
28、 nonoxygennonmetallicspeciesbyoxygen,whichresultsinamasschangeandthe developmentofasurfaceskinofalteredcomposition.Inaddition,thechemicalpotentials involvedcancausemigrationofbothmetallicandnonmetallicspecieswithinthenearsurface layer,alteringthemicrostructureofthematerial.Inthecaseofmaterialswithop
29、enporosity, suchasreactionbondedsiliconnitrideandsomesiliconcarbides,oxidationwillgenerally occurthroughcontinuousporeswhichareinitiallysurfaceconnected,althoughthesemay becomeblockedasoxidationproceeds.Theremaybeaconsequentgradientoftheextentof oxidationthroughthethicknessofasampleorcomponent. Thee
30、xtentofoxidationiscontrolledbythechemicalnatureofthematerial,itshomogeneity andthedistributionofanyadventitiousimpurities.Localconcentrationsofimpuritiesor poresintersectedbythesurfaceofthetestpiece,forexample,mayleadtolocallyenhanced oxidationandtheformationofoxidationpits. Thenatureoftheexternalsu
31、rfaceofthetestpiecewillchange.Insomecasesaglazed appearancemayresultiftheoxidationproductsareglassyincharacter,suchasinthecaseof somesiliconnitridesandsiliconcarbides.Inotherswherethesurfacelayerbecomes substantiallycrystalline,itmaybemattinappearance.Suchlayersmaybeprotectiveof furtheroxidation,ors
32、ubstantiallyslowtheprocessdowniftheyremainintact.However,in somecases,theoxidationproductmaynotadheretothesample,buttendtoflakeoffasa resultofdisruptiveforcescausedbyvolumechanges,phasechangesand/orthermalENV129232:2001(E) 6 expansionmismatchesand/orthermalcycling.Inextremecases,theoxidationlayerbec
33、omes nonprotective,andoxidationbecomescatastrophicleadingtocompletedisruptionofthe material.Thismayapplyparticularlytosomesiliconnitrideproductswhentestedinthe intermediatetemperaturerange,typically800Cto1000C. Suchchemicalandmicrostructuralchangesmayleadtosignificantvariationsinmechanical propertie
34、s.Inparticular,thenatureofstrengthdeterminingdefectsmayalter,especiallyif theyarelocatedatornearthesurfaceoftestpieces.Fulldeterminationofsuchchangesis beyondthescopeofthisPrestandard,whichislimitedinscopetodeterminationofvariations ofmass,dimensionsandroomtemperatureorelevatedtemperaturestrength.Th
35、esehave relevancetothescreeningofgeneralmaterialbehaviour,andtothemechanicalperformance ofcomponentswhichareheatedandcooled,andareexpectedtomaintainmechanical integrityatambienttemperature. 5 INTERFERENCES 5.1 Masschange 5.1.1Accuratedeterminationofmasschangesreliesonminimalcontactbetweenthetest pie
36、ceandtheapparatusinwhichitishousedforthedurationoftheoxidationtest.Ifstrong reactionoccursbetweenthetestpiecesurfaceanditssupport,asignificanterrorinregistered masschangemayresult. 5.1.2Itisrecognisedthattheoxidationreactionatedgesorcornersoftestpiecesmaybe modifiedatthesepoints,andthustheoverallmas
37、schangeperunitnominalareamaynotbe representativeofflatorgentlycurvedsurfacesalone.Theeffectmaybeminimalforoxidized layersofafewmicrometresthickness,butbecomesincreasinglysignificantforthickerlayers. Inmaterialswhichoxidizeinternallyasaresultofcontainingopenporosity,thecalculationof masschangeperunit
38、nominalsurfaceareamaybeinfluencedbythecrosssectionalshapeof thetestpiece.Resultsfromthistestmethodmaynotbedirectlyapplicabletothebehaviourof componentsofdifferentshape.However,theymayprovideabroadcomparisonofbehaviour betweendifferentmaterialswhenusingtestpiecesofthesamesizeandgeometry. 5.1.3Freecir
39、culationofthetestatmosphereisrequired.Ifthisisforanyreasonsignificantly reducedbythegeometricalarrangementoftestpiecesandsupportingapparatus,ratesof oxidationmaybereduced. 5.1.4Itshouldbenotedthatoxidationbehaviourmaybeinfluencedbythemoistureand oxygencontentsoftheatmosphere.Itisimportanttomaintaint
40、heagreedatmospheric conditionsforthedurationofthetest. 5.1.5Accuratemeasurementofmassofsmalltestpiecesmaybelimitedto0.05mg,which definesalsothelimitsofdeterminingwhetheroxidationhastakenplace.Formasschangesof thisorderofsizeorsmalleritisnecessarytoconsiderusinglargetestpieceareas. 5.1.6Thelossofmate
41、rialfromthetestpiecebyspallationorevenevaporationmayoccur.If spallationissuspected,meansshouldbeprovidedtocollectthespallationproductfromeach testpiece,butthismaynotalwaysbepossible.ENV129232:2001(E) 7 5.2 Strengthchange ThespecificationEN8431forflexuralstrengthtestingmaynotbeachievableafteroxidatio
42、n ifsurfacesbecomeroughorunevenduringoxidation.Thecorrectalignmentfunctionofthe testjigmaybeinterrupted.Sucheffectscannotatpresentbequantified.Itisrecommended thatthealignmentofthetestpieceandthetestjigischeckedafterasmallpreloadisapplied tothetestpiecebutbeforetestingtofracture. Iftheroughnessofthe
43、oxidescalecausesaproblem,attemptscanbemadetoflattenthe immediatesurfaceusingahardwoodenorsoftmetalspatula,theintentionbeingtocrush asperitieswithoutdamagingtheunderlyingdenseadherentoxidelayerortheremaining ceramicmaterial.Anysuchactionsmustbereporteddescribedinthereport. 5.3 Dimensionalchanges Meas
44、urementoftruetestpiecedimensionsafteroxidationmaybeuncertainduetothe formationofroughlayers,loosescaleorlossofscale.Thismeasurementisappropriatefor materialswhichretaincoherentoxidescales. Externaldimensionalmeasurementusingamicrometerortravellingmicroscopemaynotbe reliable,particularlyifthethicknessoftheoxidelayerislessthan0,03mm,orthe morphologyisrough.Ifoxidelayerorreaction
