Advances in Thin Film Thermocouple Durability Under High ...At NASA Lewis Research Center, thin film...
Transcript of Advances in Thin Film Thermocouple Durability Under High ...At NASA Lewis Research Center, thin film...
NASA/TM-- 1999-208812
Advances in Thin Film Thermocouple
Durability Under High Temperature
and Pressure Testing Conditions
Lisa C. Martin and Gustave C. Fralick
Lewis Research Center, Cleveland, Ohio
Keith F. Taylor
Cortez III Service Corporation, Cleveland, Ohio
January 1999
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NASA/TM-- 1999-208812
Advances in Thin Film Thermocouple
Durability Under High Temperature
and Pressure Testing Conditions
Lisa C. Martin and Gustave C. Fralick
Lewis Research Center, Cleveland, Ohio
Keith F. Taylor
Cortez III Service Corporation, Cleveland, Ohio
National Aeronautics and
Space Administration
Lewis Research Center
January 1999
NASA Center for Aerospace Information7121 Standard Drive
Hanover, MD 21076Price Code: A03
Available from
National Technical Information Service
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Springfield, VA 22100Price Code: A03
ADVANCES IN THIN FILM THERMOCOUPLE DURABILITY UNDER
HIGH TEMPERATURE AND PRESSURE TESTING CONDITIONS
Lisa C. Martin and Gustave C. Fralick
National Aeronautics and Space AdministrationLewis Research Center
Cleveland, Ohio 44135
and
Keith F. Taylor
Cortez III Service CorporationLewis Research Center
Cleveland, Ohio 44135
SUMMARY
Thin film thermocouples for measuring material surface temperature have been previously demonstrated on
several material systems and in various hostile test environments. A well-developed thin film fabrication procedure
utilizing shadow masking for patterning the sensors elements had produced thin films with sufficient durability for
applications in high temperature and pressure environments that exist in air-breathing and hydrogen-fueled burner
rig and engine test facilities. However, while shadow masking had been a reliable method for specimens with flat
and gently curved surfaces, it had not been consistently reliable for use on test components with sharp contours. This
work reports on the feasibility of utilizing photolithography processing for patterning thin film thermocouples.
Because this patterning process required changes in the thin film deposition process from that developed for shadow
masking, the effect of these changes on thin film adherence during burner rig testing was evaluated. In addition to
the results of changing the patterning method, the effects on thin film adherence of other processes used in the thin
film fabrication procedure is also presented.
INTRODUCTION
The continuous development and evaluation of both space and aeronautics propulsion systems requires surface
temperature measurement techniques that are reliable and durable in the hostile test conditions typically encountered
in burner rig and test engine environments. Reliable surface temperature data enables experimental verification of
analytical techniques that have been created to determine surface temperature distribution. Such information is rel-
evant to several research areas, including materials and structures evaluation, and fluid mechanics.
Ideally, a surface temperature measurement device that is used in burner rig or engine tests should not disturb
the conditions at the surface during testing. Wire sensors mounted on the test surface may significantly disrupt the
flow conditions. This can be overcome by installing the sensors in machined grooves in the test structure; however,
the heat transfer and temperature distribution profiles may be compromised. In addition, this procedure can alter the
structural integrity of the test component which is often unacceptable in burner rig and test engine situations.
Thin film thermocouples are intended to minimize the negative effects of placing a sensor on the surface of a
test structure. These sensors do not require that the surface be machined and are many orders of magnitude thinner
than wire sensors. As a result, thin film thermocouples add negligible mass to the surface and create minimal distur-
bance of the gas flow over the surface.
At NASA Lewis Research Center, thin film thermocouples were initially developed for superalloy turbine blade
applications for air-breathing propulsion systems (ref. 1). The technology has since been extended to other high tem-
perature material systems, including ceramic, intermetallic and ceramic matrix composite systems (refs. 2 to 3).
Additionally, the technology has been demonstrated in hydrogen-fueled test environments (refs. 2 and 4). The test
configurations have ranged from testing sensors on coupons in static furnace conditions to sensors on flat specimens
and complex shaped components in burner rig and engine test environments.
NASA/TM--1999-208812 1
Thesensorsutilizeplatinum-13%rhodium(Pt-13%Rh)versusplatinum(Pt)thermocoupleelements(standardTypeR)forhightemperaturecapabilityandaresputterdepositeddirectlyontothetestspecimenorcomponent.Thinfilmthermocoupleshavetraditionallybeenpatternedusingshadowmaskingtechniquesontestcomponentswithcurvedsurfaces,includingturbinebladesandcombustorliners.However,shadowmaskingwithstenciledstainlesssteelshimstockhasprovencumbersomeandlimitingwheninstrumentingacomponentcontainingsharpcontours.It isdifficulttoclampastiffmetalmasktothesubstratesoastosufficientlymaintainconstantmask-to-surfacecontactacrosstheentirepatternwhichisneededtopreventshadowingofthedepositedmetalfilm.Addition-ally,theheatpresentduringsputterdepositioncandistortthemaskleadingtoshadowingofthedepositedfilm.Ifseveralthermocoupleelementsarestenciledinthemetalmask,decreasedmaskstiffnessresultsmakingit difficulttosufficientlyclampthemaskbetweentheelementstopreventdistortion.Also,asfinerlinewidthsareneededforsmallerthermocouples,themaskthicknessmustbedecreasedtopreventshadowingfromthepatternedgeline.Be-causethinnermasksarelessstiff,susceptibilitytoheatdistortionincreases.Anexampleofacomponentwithsharpcontoursistheturbinebladeonwhichtheshoulderseparatingtheairfoilandshankareasprotrudesoutfromthebladesurfaceatasharpangleandpresentslimitedspaceforclampingametalmask.Spaceshuttlemainenginetur-binebladeshavebeenshadowmaskedforthinfilmthermocoupleswithgreatdifficultyoverthisbladearearesultinginlowsuccessrateswhenfabricatingworkingthinfilmsensors(refs.2and4).It ispreferabletohaveanalternativemaskingmethodthatisreliableforuseonthesetypesofchallengingshapes.
Theworkpresentedhereindiscussestheviabilityofusingphotolithographymaskingtechniquestopatternthinfilmthermocouplesforapplicationsinburnerrigandenginetesting.Photolithographyemployspatternedphoto-maskswhichareplacedonthesurfaceafterapplicationofphotoresistandarethenexposedtoultravioletlight.Thecomponentwithapatternedlayerofphotoresistis thendepositedwiththesensormaterial.Becauseexposureoccursatroomtemperatureandthephotomaskisnolongerneededafterpatterningthephotoresist,maskdistortionduringsputterdepositionisnotaconcernasit isformetalmasks.Photomasksalsoofferflexibilityin thatpatternswithfinelinegeometriesareachievable.Thisisvaluableinapplicationswhereseveralthermocouplesareneededinasmallspacewhichdictatesthatthesensorelementwidthsbesmallerthanwhatisreliablyfeasiblewithmetalmasks.Flex-iblephotomaskshavebeenfabricatedwithmylarfilmwhichconformtothecomponentshapetherebymakingthephotolithographyprocessapplicabletocurvedsurfaces(ref.5).
ThefabricationprocedureutilizingshadowmaskingthathadbeendevelopedforthePt-13%RhversusPtthinfilmsensorshasproducedfilmsthatweresuccessfullytestedinvarioustestenvironments.However,thisfilmdepo-sitionprocedurehadtobealteredtoaccommodatethetemperaturelimitsimposedbythematerialsusedinthepho-tolithographyprocess.Theresultantfilmswerethentestedfordurabilityonflatspecimensinahydrogen-fueledrocketenginetestfacility.Thetestfacilitywasalteredtoprovidehighpressureconditionsinaspecimentestcham-ber.Previouslyreportedtestsinthisfacilitylimitedthespecimenstohightemperaturegasexposurewhilemountedintheengineexhaustplane(refs.2and4).Whilethistestwasdesignedforareusablelaunchvehicleapplication,theresultsarerelevanttothinfilmsensorapplicationsforairbreathingpropulsioncomponentsaswell.
Inadditiontoinvestigatingtheeffectonfilmdurabilityofalteringthedepositionparameterstoaccommodatethephotolithographymaskingtechnique,twoadditionalfabricationparameterswerelookedattodetermineif therewasanyinfluenceonfilmdurabilityduringhightemperatureandhighpressuretesting.Theeffectofusingfinepowdergritblastingtopreparethesurfacepriortofilmdepositionwasexaminedtodetermineif it aidedfilmadhe-sionduringtesting.Additionally,twodepositionmethods,sputterdepositionandelectronbeamevaporation,werecomparedtodeterminetheeffect,if any,ofdepositionmethodonthedurabilityandadhesivestrengthofthedepos-itedaluminumoxidelayer.Thefunctionofthislayerwastoelectricallyinsulatethethermocoupleelementsfromtheconductingsubstratematerial.
SENSORFABRICATION
Asshownintheschematicin figure1,thinfilmthermocouplesarecomposedof several layers. The substrates,
2.5 x 12.7 x 0.318 cm (1 x 5 x 0.125 in.), were a nickel-based superalloy, Mar-M 246, which is stock material for
first stage turbine blades used in the high pressure fuel turbopump of the space shuttle main engine. The metal ther-
mocouple elements were electrically insulated from the metal substrate by a layer of aluminum oxide. Several steps
were used to prepare this layer. A 125 Hm (0.005 in.) thick coating of PWA 270 NiCoCrA1Y (12 wt% Co, 18 wt%
Cr, 12 wt% A1, 0.3 wt% Y and balance Ni) was electron beam vapor deposited onto the substrates. The coating was
then glass bead peened to increase its density. Half of the twenty samples were grit blasted with 27 Hm aluminum
NAS A/TM-- 1999 -208812 2
oxidepowderinordertostudytheeffectsonfilmadhesionoflightlyrougheningthecoating.All ofthesampleswerethencleanedinmicrosoapanddeionizedwaterandheattreatedinvacuumat1000°C(1800°F)tofacilitatemigrationofaluminumtothesurface.Thiswasfollowedbyanoxidationheattreatmentinairat1000°C(1800°F)tothermallygrowaluminumoxidewithathicknessontheorderof 1to3_tm.Toformapinhole-free,crack-freeelectricallyinsulatingfilm,anadditionallayerofaluminumoxidewasdepositedontothegrownaluminumoxide.
Fortheremainingprocessingsteps,amatrixoffabricationstepswascreatedinordertodeterminetheeffects,ifany,ofeachprocessonfilmadhesionpropertiesduringtestinginharshconditions(tableI).Foreachsetofsamples,oneprocessingparameterwaschangedwhiletheotherparameterswereheldconstant.Sputterdepositionwasusedtodepositaluminumoxideonhalfofthesamplesandelectronbeamvapordepositionwasusedfortheremainingsamples.Sputterdepositionoccurredinthediodemodeinpureargonatapowerdensityof3.09W/cm2.Thesput-teredaluminumoxidefilmswere-2 to3_tmthick.Fordepositionbytheelectronbeamvapordepositionprocess,asubstrateheaterwasmaintainedat900°C.Theevaporatedfilmswere-4 to5_tmthick.Theelectronbeamvapordepositionprocessofferstheadvantageofbeingamuchfasterprocessthansputterdepositionwithprocesstimesof<1hrversus10to20hrfordepositingfilmsofthesethicknesses.Thesampleswerethenreadytobepatternedforthethermocoupleelementspriortometaldeposition.
PerthematrixintableI,halfofthesampleswerepatternedwith0.025cm(0.010in.)thickstainlesssteelshimstockmasksthathadbeenmachinedwithathermocoupleelementpattern.Themetalmaskswereclampedontothesamplesurfaceandsputterdepositedwitha3to5_tmthickplatinumlayer.Themetalsweresputterdepositedinmagnetronmodeatapowerdensityof2.47W/cm2.Aheaterlocatedatanadjacentsputterstationwasmaintainedat400°C.Forthefirstseveralthousandangstromsofdepositedmetal,oxygen-enhancedsputterdepositionwasusedtoaidfilmadhesiontothealuminumoxidelayer.Themaskinganddepositionprocesswasthenrepeatedfortheplatinum-13%rhodiumelement.
Theremainingsampleswerepatternedviathephotolithographyprocess.Fortheliftofftechnique,positivepho-toresistwasfirstappliedtothesurface.Becausethispatterningwasforthedepositionofrelativelythick(3_tm)metalfilms,thephotoresistlayerwasthicker(-3_tm)thanthattypicallyusedinphotolithographyprocessesforthemicroelectronicsmanufacturingindustry(<1_tm).Subsequentstepsincludedexposuretoultravioletlightofthephotoresistthroughapatternedmaskandprocessingindevelopertoremovetheexposedphotoresist.Someunder-cuttingoccurredatthephotoresistlineedgesthatwouldlaterallowgreatereaseinremovingthephotoresistandoverlyingdepositedmetal.Thespecimenswerethenbakedatlowtemperature(90°C,190°F)toremoveanyremainingmoisturefromthephotoresistlayer.
Theuseofpositivephotoresistforpatterningthethermocoupleelementslimitsthetemperaturetowhichthesamplecanbeexposedduringsputterdeposition.Asaresult,somedepositionparameterswerealteredtopreventoverheatingandsubsequentdamagetothephotoresist.Whenphotoresistisdamagedin thisway,thesolventisunabletoremovethephotoresistandoverlyingmetalfilm.Duringmetaldeposition,thespecimenswerepositionedonacooledsubstrateholdermaintainedat0°C.Platinumwassputterdepositedindiodemodeatapowerdensityof1.10W/cm2.Oxygen-enhancedsputterdepositionwasusedforthefirstseveralthousandangstromsofdepositionandthemetalfilmswere-3 to4_tmthick.Afterdepositionoftheplatinumlayer,thephotoresistandoverlyingmetalwereremovedbysoakinginacetone.Theprocessingstepswerethenrepeatedfortheplatinum-13%rhodiumlayer.
Despitestepstakentopreventoverheatingthephotoresistduringdeposition,thesampleswerenotevenlycooledacrossthesurfaceresultinginsomeareasofphotoresistdamage.Consequently,thesolventwasunabletocompletelyremovethephotoresistfromtheentiresurface.Thiswasevidentbyscatteredmetaldepositsonthesur-faceaswellaspooredgelinesforsomeofthethermocouples.Inseverecases,linesofscatteredmetaldepositscrossedbetweenthetwothermocoupleelementsresultinginshortingbetweentheelements.
Figure2isaphotographofasampleinstrumentedwithathinfilmthermocoupleelementpattern.Theindi-vidualelementlengthandwidthwere10.64cm(4.188in.)and0.159cm(0.063in.),respectively.Thejunctionatwhichthetwoelementsmetwasthesurfacetemperaturemeasurementpointandwas-0.318cm(0.125in.)by0.635cm(0.250in.).Thethermocoupleswerefabricatedwithenlargedleadwirepadstoallowgreatereaseinliningupthebareleadwireswiththethinfilmelementspriortoclampingandinstallationintothetestrig.
Inall,therewereeightgroupsofspecimens,eachrepresentingauniquesetofdepositionparameters(tableI).All ofthespecimenswereannealedfor20hrat1000°C(1800°F).Theleadwireswere75_tm(0.003in.)diameterplatinum-13%rhodiumandplatinumbarewiresthatwereclampedtothefilmspriortoinstallationintherocketlaboratoryfacilityfortesting.
NASA/TM--1999-208812 3
ROCKETLABORATORYTESTFACILITY
Therocketlabfacilityinwhichthespecimensweretestedutilizesagaseoushydrogenandoxygenrocketcom-bustortogeneratehightemperature,highheatflux,hydrogen-oroxygen-richhotgasenvironments(ref.6). Thisfacilityapproximatesthethermalshockconditionsofthespaceshuttlemainengineturbopumps.Gastemperaturesrangingfromabout1000to2700°C(1800to5000°F)areobtainableatcombustionchamberpressuresupto4.1MPa(600psi).Forthesetests,theenginewasoperatedatfuel-richratios(O2:H2massflowrateratioof 1.0)resultingingastemperaturesof-900to1100°C.Unlikeprevioustestsinwhichthesamplesweremountedintheexhaustplaneoftheengine(refs.2and4),thesamplesweremountedinspeciallydesignedhardwarewithinthecombustionchamber.Thisprovidedfortestingthespecimensunderhigherpressureconditionsof-3.4MPa(500psi).Thefacilitywasinstrumentedwithapressuresensorformonitoringthepressureprofilewithinthecom-bustionchamber.Thethinfilmthermocouplejunctionwaslocatedapproximatelyinthecenterofthegasflowwithinthecombustionchamber.Thetestdurationwas3sec/run.Thetestrunswerereducedto3secfrom5secusedinprevioustests(refs.2and4) duetoconcernswithoverheatingofthetestchamberhardware.If afilmwasintactafterone3-sectestrun,it thenunderwentadditionaltestrtms.
Fortheinitialtests,thesamplesweremountedwiththesensorsurfacepositionedparalleltothegasflow.Thosesamplesthatperformedwellundertheseconditionswerethentestedwiththesamplesurfacepositionedata22.5°angleintotheflow.Additionaltestingwasperformedonthesurvivingfilmswiththesamplesurfaceata45° angleintotheflow.Thispositionallowedforgreaterimpactofthecombustiongassesonthethinfilmsensors.Notallofthepreparedsamplesweretestedin thefacility.Thosesamplesthatdidnotgivetemperatureoutputduetoabreakinfilmcontinuitywerenottested.
RESULTSANDDISCUSSION
Thethreefabricationprocessesoutlinedabovewereevaluatedforeffectonfilmdurabilityunderhightempera-tureandhighpressureconditions.Sputteredaluminumoxidefilmsandelectronbeamvapordepositedaluminumoxidefilmsdidnotdemonstrateanyappreciabledifferenceinabilitytoaidtheadhesionofthethermocoupleele-mentstothesubstrateduringtesting.Thisevaluationwasbaseduponcomparingallofthesamplesthatwerepro-cessedwithsputtereddepositedaluminumoxidewiththosethathadelectron-beamvapordepositedaluminumoxide.Approximatelythesamepercentageofeachsetofsampleshadintactfilmsaftertesting.Thesamplesthathadbeengritblastedpriortothinfilmprocessingdemonstratedgreaterdurabilitythanthosesamplesthathadbeenleftasis.Theformersetofsampleshadabout50percentwithintactfilmsversusonly20percentwithintactfilmsforthelatterset.ThelightrougheningoftheNiCoCrA1YsurfacemayhaveallowedforsomedegreeofmechanicalinterlockingbetweenthedepositedaluminumoxideinsulatinglayerandtheunderlyingNiCoCrA1Yandthermallygrownaluminumoxidelayers.
Severalsamplespatternedwiththephotolithographyprocessperformedverywellduringtesting.A setofthreesampleswhichhadprocessingproceduresthatincludedgritblastingtheNiCoCrA1Ycoating,sputterdepositionofaluminumoxide,andthephotolithographymasksurvivedallofthetestrunsintherocketlabprocess(samplegroupno.4in tableI).A totalofsixtestrunseachwereconductedontwoofthesamplesandthethirdunderwentthreetestruns.Thesamplepositionsvariedbetweentestrunsandincludedorientationsof0,22.5,and45° anglestothegasflow.All ofthefilmswereintactattheconclusionofthetests.Whilethefocusofthesetestswasfilmadhesionanddurability,temperaturedatawerealsocollected.Figure3includessurfacetemperatureandpressuredatameas-uredinthecombustionchamberduringonetestrun.Thesamplewasorientedata0° angletothegasflow.Thethinfilmthermocouplemeasuredamaximumsurfacetemperatureofapproximately580°C(1080°F)priortoshutdown.Thenominalchamberpressurewas-3.5MPa(510psi).Becausethetestrtmwasfor3seconly,it isexpectedthatthesurfacetemperaturewouldnotapproachthegastemperature,thereforethemeasuredsurfacetemperatureisreasonable.Theapparenttemperaturespikein thedataaftershutdownwaspresentinthedatafromallofthetestrunsandis likelyduetosometypeofelectricalinterferenceintheinstrumentationsystem.Withsubsequenttestruns,themaximumsurfacetemperatureoutputdiddemonstrategradualdegradation,evenasthesampleswereori-entedtowardstheflow.Thismaybeattributabletogradualerosionofthethinfilmmaterialduringeachadditionaltestrunthusaffectingthesensoraccuracy.Thiseffectcanbedelayedwiththeapplicationofaprotectivealuminumoxideovercoatfilmflinthasbeenutilizedinpreviouswork(refs.2and4).
NASA/TM--1999-208812 4
Becausetraditionalwirethermocoupleshaveprovenunabletowithstandthetestconditionsinthisfacility,nogastemperaturedatacouldbecollectedsimultaneouslytoverifythethinfilmthermocoupledata.However,thefactthatthetemperatureprofilein figure3correspondstothechamberpressureprofileindicatesthatthethinfilmther-mocoupleswereoperatingnormally.Thismarksthefirsttimethattemperatureswithinthecombustionchambercouldbemeasuredin thisfacility.
Whilethefilmspatternedwithphotolithographyperformedwellinthesetests,improvementsarestillneededtomakethisareliable,repeatableprocess.Inordertopreventpotentialshortingacrossthethermocoupleelementsduetostraymetaldepositsoutsidetheelementspattern,theprocessforremovingthephotoresistafterdepositionmustbeimproved.Moreconsistentcoolingacrossthespecimenduringsputterdepositionisneeded.Additionally,othersolventssuchascommercialstripperscanbeinvestigatedthatmayremoveheat-damagedphotoresistmoreeasilywithoutcausingdamagetothedepositedmetalfilms.Finally,increasingthethicknessofthephotoresistlayerrela-tivetothatofthemetalfilmmayalsoincreaseeaseofphotoresistremoval.
Sincethemetaldepositionparametersusedforthespecimenspatternedwithphotolithographyproducedfilmsdurableforapplicationsinburnerrigandenginetesting,itwouldbeofinteresttodetermineif thesesameparam-eterscoupledwithmetalshadowmaskswouldalsoprovidedurablefilms.Ofparticularinterestistheeffectofsub-stratecoolingduringsputterdepositiononthefilmadherencesincepastworkhaddemonstratedtheeffectivenessofsubstrateheatinginforminghighlyadherentfilms.It isexpectedthatsubstratecoolingwouldeffectivelyeliminatethemetalmaskdistortionthatoccurswithsubstrateheatingandthehigherpowerdensitiesusedfortheshadowmaskedspecimens.Thisshouldthenreducetheoccurrenceoffilmshadowingoutsideofthepatternedthermocoupleelements.Additionally,thinnermetalmaskscouldthenbeusedformultiplethermocouplesandsmallerlinewidths.If filmsfabricatedwiththesedepositionparametersprovedtobeconsistentlydurablewhenusedwitheithershadowmaskingorphotolithography,thiswouldallowtheflexibilityofutilizingeitherpatterningmethodasneededforanyparticularapplication.Additionalsensorfabricationandtestingisrequiredtodeterminethedurabilityandreliabilityofsuchfilms.
CONCLUSIONS
Thepreliminaryworkdescribedhereindemonstratedthatreplacingthe shadow mask procedure with a photoli-
thography mask procedure is a viable means for patterning thin film thermocouples to be used in high temperature,
high pressure burner rig tests. Films fabricated with deposition procedures designed to accommodate the low tem-
perature requirements for using photoresist proved to be durable in a harsh test environment. While a possible
method for patterning thin film sensors on complex shaped components, improvements are needed to make photoli-
thography a reliable, repeatable process. In particular, the process for removing the photoresist after deposition must
be improved. The deposition process used for photolithography may also have potential for use with shadow mask-
ing. Additional work is needed to determine the viability of using the low temperature deposition process for both
photolithography and shadow masking techniques. The effect of fine powder grit blasting in improving thin film
adherence was also demonstrated. A comparison of deposition methods for aluminum oxide did not yield a clear
advantage of either sputter deposition or electron beam vapor deposition in improving film adherence. Finally, these
tests with thin film thermocouples marked the first time in which surface temperature was measured within the com-
bustion chamber of this rocket lab test facility. Previous use of wire sensors had proven unreliable and insufficientlydurable to withstand the harsh environmental conditions.
REFERENCES
1. Grant, H.P., Przybyszewski, J.S., and Claing, R.G.: "Turbine Blade Temperature Measurements Using Thin
Film Temperature Sensors," PWA-5604-31, Pratt and Whitney Aircraft, NASA Contract NAS3-20831,
NASA CR-165201, 1981.
2. Martin, L.C., and Holanda, R.L.: "Applications of Thin Film Thermocouples for Surface Temperature Measure-
ment," SPIE/NASA Conference on Spin-Off Technologies for Commercial Sensors and Scientific
Instrumentation, San Diego, CA, July 1994.
NASA/TM-- 1999-208812 5
3. Martin,L.C.,andWill,H.A.:"ThinFilmThermocoupleApplicationsinBurnerRigTestingofCeramicMatrixCompositeHardware,"HITEMPReview1997:AdvancedHighTemperatureEngineMaterialsTechnologyProgram,NASACP-10192,1997.
4. Martin,L.C.:"TestingofThinFilmThermocouplesinRocketEngineEnvironments,"AdvancedEarth-to-OrbitPropulsionTechnology,NASACP-3282,1994.
5. Will,H.A.,andBhatt,H.:"StatusofThinFilmHeatFluxSensors,"AdvancedEarth-to-OrbitPropulsionTechnology,NASACP-3282,1994.
6. Green,J.M.:"A VersatileRocketEngineHotGasFacility,"AIAAAerospaceGroundTestingConference,AIAA-94-2487,1994.
TABLE I._ABRICATION PROCESSES FOR TEST SAMPLES
Sanlple Nunlber of
group samplesnumber
1 2
2 3
3 2
4 3
5 3
6 2
7 2
8 3
Thernlocouple
patterningtechnique
Grit blast prepm'ation A1203 deposition
process
Shadow masking None Sputter deposition
Photolithography None Sputter deposition
Shadow nlasking 27 pin A1203 powder Sputter deposition
Photolithography 27 pin A1203 powder Sputter deposition
Shadow nlasking None E beam vapor
Photolithography None E beam vapor
Shadow nlasking 27 pin A1203 powder E beam vapor
Photolithography 27 pin A1203 powder E beam vapor
NAS A/TM-- 1999 -208812 6
Thermocouple Elements 3-5gin
Deposited AI203 2-5gin
Thermally grown AI203 1-2
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
iiiiiiiiiiNii_i_CirAil_ii_ialii iiii_i2iSi_i_iiiiiiiiii:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
Figure 1.--Schematic of thin film
thermocouple layers.
Figure 2.--Test sample instrumented with thin film thermocouple.
NASA/TM-- 1999-208812 7
{530
0r_E
900
800
700
6OO
500
400
300
2OO
100
- 1O0
Thin Film Thermocouple
Chamber Pressure
1 2 3 4 5 6 7 8
Time, seconds
Figure 3.--Temperature and pressure data from thin film thermocouple burner rig test.
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
ulul
m
NAS A/TM-- 1999-208812 8
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4. TITLE AND SUBTITLE 5. FUNDING NUMBERS
Advances in Thin Film Thermocouple Durability Under High Temperature and
Pressure Testing Conditions
6. AUTHOR(S)
Lisa C. Martin, Gustave C. Fralick, and Keith F. Taylor
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)
National Aeronautics and Space Administration
Lewis Research Center
Cleveland, Ohio 44135- 3191
9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)
National Aeronautics and Space Administration
Washington, DC 20546- 0001
WU-537-04-22-00
8. PERFORMING ORGANIZATION
REPORTNUMBER
E-11407
10. SPONSORING/MONITORING
AGENCY REPORT NUMBER
NASA TM--1999-208812
11. SUPPLEMENTARY NOTES
Lisa C. Martin and Gustave C. Fralick, NASA Lewis Research Center; Keith F. Taylor, Cortez III Service Corporation,
Cleveland, Ohio 44135. Responsible person, Lisa C. Martin, organization code 5510, (216) 433-6468.
12a. DISTRIBUTION/AVAILABILITY STATEMENT
Unclassified - Unlimited
Subject Categories: 35, 07, and 20 Distribution: Nonstandard
This publication is available from the NASA Center for AeroSpace Information, (301) 6214)390.
12b. DISTRIBUTION CODE
13. ABSTRACT (Maximum 200 words)
Thin film thermocouples for measuring material surface temperature have been previously demonstrated on several
material systems and in various hostile test environments. A well-developed thin film fabrication procedure utilizing
shadow masking for patterning the sensors elements had produced thin films with sufficient durability for applications in
high temperature and pressure environments that exist in air-breathing and hydrogen-fueled burner rig and engine test
facilities. However, while shadow masking had been a reliable method for specimens with flat and gently curved
surfaces, it had not been consistently reliable for use on test components with sharp contours. This work reports on the
feasibility of utilizing photolithography processing for patterning thin film thermocouples. Because this patterning
process required changes in the thin film deposition process from that developed for shadow masking, the effect of these
changes on thin film adherence during burner rig testing was evaluated. In addition to the results of changing the
patterning method, the effects on thin film adherence of other processes used in the thin film fabrication procedure is
also presented.
14. SUBJECT TERMS
Thin films; Thermocouple; High temperature measurements; Hydrogen flame temperature
17. SECURITY CLASSIFICATIONOF REPORT
Unclassified
NSN 7540-01-280-5500
15. NUMBER OF PAGES
]416. PRICE CODE
A0318. SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATION 20. LIMITATION OF ABSTRACT
OF THIS PAGE OF ABSTRACT
Unclassified Unclassified
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