ai-aerospace/ams_data_full_2000-2020 huggingface dataset:
usedforthestructuralanalysis.Figure19showstheseresultsforthefirst4modesofvibrationconsidered importantfortherangeofinputfrequencies andacombination ofallthefourvibrationmodes. 622.9Hz 451.2Hz 736.0Hz 1082.0Hz Combined Figure19.MajorVibration Modes oftheBearing Theimplication ofthevibration analyses, withrespect tothebearing fault(question 1intheFailure Analysis section above), isthatthefree-body naturalfrequency (123Hz)hasnoeffectonthefailure. The failure isconsidered theresultofacombination ofmodes resultant ofapeakinthesteady-state transmissibility function fortheout-of-plane axisnear600Hz. Importantly, thesemodesaredetermined by thebearing system itself. Practical Solution Theimportant factfortheprogram athandwastheidentification ofthecorrelation between thefailureand the600Hzcomponents. Recallthatthetestregime wasaspecialtestatdevicelevelagainst anartificial specandwasfurtherexacerbated bythehighQofthespringboard fixture. Thefindings allowed further investigation atpayload levelandeventually itwaspossible toavoidthe600Hzcomponent entirely. Once thecomponent wasnolongerover-excited thefailuredisappeared allowing theprogram tobefinished in time. Itispossible thatthebearing behavior maybeimproved byincreasing thenumber ofballsthatwillhave asresultachange ofthenatural frequencies depicted inFigure 19towards highervalues. Itisalso possible thatadifferent retainer pocketdesign(suchasakeyhole profile) willprovemorerobusttothis kindoffailure.This,however, ispurelyintuitive andrequires research. Animportant observation isthatthe ejection waspurelymechanical, without wearordeterioration andwouldhavebeencontained hadthere beenshoulder orshieldstructures toimpede theretainer. NASA/C P--2002-211506 303
Conclusion andLessons Learned 1.Ejection ofcrownretainers undervibration isapotential failuremodeofbearings. ,Classical bearing selection methods basedonstaticanddynamic loadcarrying capacity andstandard dataprovided bybearing suppliers donotpredictthistypeoffailure,noristheresubstantial literature onthesubject. 3.Caution mustbeexercised whensuchbearings areusedinhighvibration environments. Thecorrect vibration profileisimportant inproving thereliable operation ofthemechanism. 4.Inanalyzing forhighvibration environments, bearing properties maybesignificant. .Theriskofretainer ejection canbemitigated inmanycasesbyextending shaft/housing shoulders beyond thebearing land.Inmostdesigns, stabledislocation orirreversible ballmigration require the retainer todisplace beyond theframeendface. 6.Thereismeritinfutureinvestigation bybearing specialists toidentify robustretainer designs and application criteria. References 1.Meirovich, L.Analytical Methods inVibrations. Macmillan: NewYork,@1967. 2.Thomson, W.TheoryofVibration withApplications 2ndEdition. Prentice Hall:NewJersey, @1981. 3.Steinberg, DavidS.Vibration Analysis forElectronic Equipment. Wiley-lnterscience: NewYork,@1988. 4.F6ppl,A.Vorlesungen fibertechniche Mechanik. Band1-3,Oldenburg Verlag: MQnchen, @1949-1951. 5.NASATMX-73306 Astronautic Structures Manual. Vol.2,George C.Marshall SpaceFightCenter, Structures andPropulsion Laboratory, 1975,section B9. 6.MIL-HDBK-5H Metallic Materials andElements forAerospace Vehicle Structures. DOD:Washington, 1998. 7.DesignGuideSeries, RollingBearings, Version 1.0fromMulti-media Handbook forEngineering Design, DesignInformation Group,University ofBristol,UK. 8.TedricA.Harris,RollingBearing Analysis. JohnWiley&Sons:NewYork,@1984, FirstandSecond Edition. 9.E.G.Gargiulo jr.,E.I.DuPont deNemours andCo.Wilmington DE.,Machine Design, July24,1980. NASA/CP--2002-211506 304
a0.476cmradius(3/8inchdiameter)commercial grade10,440Cballthathadthesamesurface roughnessasthedisks.ThehardnessoftheballswasRockwellC-60. Table1.TypesofMoS2Coatings Evaluated inthisStudy. Vendor's Name Designation MajorAdditive Coating Thickness(p.m) Movic Movic None 0.6 Surftech Surftech None 0.3 Hohman Plating Hohman Antimony Trioxide 1.2 Teer Teer-Ti Titanium 1.2 CSEM CSEM-Ti Titanium 2.4 CSEM CSEM-AI Aluminum 3.5 Testing Apparatus Pin-on-Disk Tribometer Thepin-on-disk Tribometer usedinthisstudy(Figure 1)hasbeendescribed indetailinReference 21. Thespecimens consisted ofaflatrotating disk(6.3-cm diameter) inslidingcontact withastationary ball (0.476-cm radius)thatwassecurely fastened inaholder.Theballslidondisktracksthatrangedfrom6.0 cmto4.4cmindiameter. Therotational speedofthediskwascontrolled at200rpmgivinglinearsliding speeds of0.63to0.46m/s.Thetestspecimens wereencased inaplasticboxtocontroltheatmospheric moisture content. Theloadof9.8N(1kg)wasapplied totheballbyadeadweightusingaleverarm system. Astraingagewasusedtomonitor andmeasure thefrictional force. Wearvolume oftheballwasdetermined bymeasuring thechange indiameter ofawearscarontheball andthencalculating thevolume ofmaterial removed. Wearvolume ofthediskwasdetermined by measuring theweartrackcross-sectional areausingasurface profilometer andthencalculating the volume ofmaterial removed. Adiscussion onhowtoevaluate solidlubricants inapin-on-disk testeris giveninthenextsection andinthereference byFusaro [21]. ....Applied load Strain gauge . .: ., _._.rCounter Motor ..... W........ i _,-:_-_Ti:::i_;;_ ::-{__._.. -;__-:pEnvironmental .._-----:: :.""._:_Y;":'_'_- ;,4..},-"'_'_ Ichamber _-_L;.........."..(,_.4.i1":.5"-:_-:._-_-_..... I ..----:_.-:..-,. . .• -..-.,".._-_>" ,,' ' .......Preload ." ". ....:"--.:-:::.: ....::.-_;:-...... • "Disc .....Ballholder Gimbal ." assembly ." Translation plate Figure1.Schematic ofPin-on-Disk Tribometer Block-on-Rinq Tribometer Aschematic oftheblock-on-ring testelements isshowninFigure2.Asshowninthefigure,thedevice consists ofarectangular block(0.6cmwidex2cmlongx1cmhigh)pressed against theperiphery ofa ring(1cmwidex5cmdiameter). Theblockcanbeflat(linecontact) oritcanbeconforming (area contact). Inthisstudyonlylinecontact wasused. NASA/CP--2002-211506 306
Theblockandtheringusedinthisstudyweremadefrom440Cstainlesssteel.Theblockwasstationary andloadedwithadeadweightagainstthering.Theringwasattachedtoarotatingshaftthatcanrotatein onedirection.Aprobeattachedtotheblockholdercontactsaloadtransducer andmeasuresfrictional forcebetweentheblockandtherotatingring.Athermocouple isimbeddednearthecontactareaofthe blocktomeasuretemperature. Thecoatingwasappliedtothecontactareaaroundtheoutsidediameteroftheringandtothe(0.6x1.5 cm)faceoftheblock.Inallcases,thesurfaceroughnessoftheblockisveryimportantandcaninfluence theresults.Tomostcloselyreproducetheend-useapplication, theroughnessshouldcloselymatchthat value.Inthiscase,thesurfaceswereverysmooth(0.05to0.10X10-6mRa).Theslidingconditionsfor theblock-on-ring testwereasfollows:slidingspeed,500rpm,load,225newtons,temperature, 25°C. Load Thermocouple Access\ //--Contact Hole--_ Block  __Ring Rotation Figure2.Schematic ofBlock-on-Ring Tribometer Specimens Procedure Surface Preparation andCleaninq Procedure Thecleaning procedure forthespecimens beforetheyweresenttothevendor wasasfollows: 1)Scrubsurface underrunning waterwithabottle-brush toremove abrasive particles. 2)Cleansurfaces withpureethylalcohol usingalint-free cloth. 3)Scrubsurface withawaterpasteoflevigated alumina. Cleanuntilwaterwetsthesurface readily. 4)Rinsethesurface underrunning watertoremove thelevigated alumina (usingthebrushtofacilitate removal). 5)Rinsethesurface indistilled water. 6)Drysurfaces usingdrycompressed air.(Surfaces notdriedquicklyhaveatendency tooxidize.) Pin-on-Disk Testinq Procedure Theprocedure forconducting thepin-on-disk experiments wasasfollows: apin(ball)andadisk(with applied sputtered UoS2coating) wereinserted intotheTribometer testchamber (Figure 1).Thetest chamber wassealed, anddryair(<100-ppm H20),ormoistair(-10,000-ppm H20)waspurged through thechamber for10minutes beforestarting thetestandthencontinuously throughout thetest.Whenthe purgewascompleted, thediskwassetintorotation at200rpm.A1-kilogram (9.8Nloadwasthen applied tothediskasitrotated. Somepreliminary experiments wereconducted todetermine thefriction characteristics ofunlubricated 440Cstainless steelslidingonitself.Fromthoseresults, itwasdecided tomakethecriterion forfailurefor theseteststobeafrictioncoefficient of0.30,muchlessthanthefrictioncoefficient ofunlubricated 440C stainless steel(>0.60). Anautomatic cutoffsystem wasusedtoshutdowntheapparatus whenthefriction coefficient reached 0.30. NASA/C PP2002-211506 307
Twotypesoffrictionandweartestingprocedures werefollowed:(1)the"continuous testingmethod"and (2)the"intervaltestingmethod."Inthecontinuous testingmethod,thetestwasruncontinuously untila frictioncoefficientof0.30occurred.Thespecimens wereremovedfromtheTribometer andthewear scarsweremeasuredusinganopticalmicroscope andthecoatingwearwasmeasuredusingasurface profilometer. Thevisualmicroscope wasalsousedtoevaluatethemorphology oftheslidingsurfacesat magnifications to3000X.Thenumberofrevolutions toreachthisvalueoffrictioncoefficientwasdefined astheendurance lifeofthecoating.Inthe"intervaltestingmethod,"thespecimens wereremovedfrom thetestchamberatpredetermined intervalsofslidingandthespecimencontactareaswereevaluatedas inthecontinuous testingmethod.Thespecimens werethenplacedbackintothechamberandthe previoustestprocedureisrepeated.Slidingcontinueduntilafrictioncoefficientof0.30wasobtained.The advantageoftheintervalmethodisthatwearasafunctionofslidingdistancecanbedetermined andthat thetypeofwearoccurringonthesurfacesbeforefailurecanbestudied.Incontinuous testing,onlywear attheendofatestcanbedetermined andrun-inwearcannotbeseparatedfromsteady-state wear.One caveatonthe"intervaltestingmethod"isthatcaremustbetakentoreplacethespecimens withthesame orientationandalignmentthattheyhadbeforetheywereremoved.Livesfrombothmethodswerenearly identicalinair,althoughaslightfriction"run-in"occursatthestartofeachintervaltest. Block-on-Rinq TestProcedure Thespecimens wereinserted intotheapparatus andthechamber sealed. Thechamber wasthenpurged withthenitrogen beforestarting thetestfor10minutes andthencontinuously throughout thetest.This procedure wasrepeated eachtimeatestwasstopped untilthetestwascompleted. Boththecontinuous testingmethod andtheinterval testingmethod (asdescribed above) wereusedfortheseexperiments but theywerenotstopped asmanytimesasforthepin-on-disk tests.Thiswasdonebecause ofconcern that thesurfaces mayhaveexperienced oxidation degradation duringthetimetheywereremoved. Results andDiscussion Pin-on-Disk Friction Coefficient Friction coefficient foreachpin-on-disk experiment wasconstantly monitored though outthetests.Table 2andFigure3present thesteady-state frictioncoefficients forallcoatings testedinbothmoistairanddry air.Thelowestfrictioncoefficient of0.04wasobtained indryairfor4ofthefilms,theMovic,theSurftech, theHohman andtheTeer-Ti coatings. TheCSEM-Ti coating produced afriction coefficient of0.06and theCSEM-AI coating produced africtioncoefficient of0.08. 0.16  ::•DryAir '_'0.14--- ........................................... ._=0.12__/_J I_MoistAir 0.1...........................o ,,o.o 20 -- Movic Surftech Hohman Teer-Ti CSEM-Ti CSEM-AI TypeofSputtered MoS2 Coating Figure3.Average Steady StateFriction Coefficient fordifferent sputtered MoS2films(obtained fromvarious vendors) andtestedinmoistairanddryaironapin-on-disk Tribometer. TheSurftech coating alsoproduced asteady-state frictioncoefficient of0.04inmoistair,butalltheother coatings produced muchhigherfrictioncoefficients inmoistairthandryair.Inmoistair,Movicproduced thehighest frictioncoefficient of0.15,thevaluefortheHohman andtheCSEM-AI coatings was0.12,the NASA/CP--2002-211506 308
CSEM-Ticoatingwas0.11andtheTeer-Ticoatingwas0.09.Forvacuumapplications, thefriction coefficients indryormoistairarenotreallyrelevantexceptforthefactthathigherfrictioncoefficients usuallymeanhigherwearandalsoshorterlives.Itmayalsobeusefulinformation fordesigning components thatmighthavetooperatebothinairandinvacuum.WithMoS2coatingsingeneral,friction coefficientismuchmoreaffectedbywatervaporthanoxygen,thusfrictionindryairmoreclosely approximates thefrictionthatwouldbeobtainedinvacuum. Table2.Pin-on-Disk TestResults MoS2 Coating Movic Surftech Hohman Teer-Ti CSEM-Ti CSEM-AISteady-State Friction Coefficient Moist Dry Air Air 0.15 0.04 0.04 0.04 0.12 0.04 0.09 0.04 0.11 0.06 0.12 0.08Endurance Life (Kilocycles)Counterface WearRate (maimx10-18) 100+26Coating WearRate (m3/mx1018) 145+135Moist Dry Moist Dry Moist Dry Air Air Air Air Air Air 7+3 120+17700+3004+2 ...... 39+6 41+7 15+12 3+1 ...... 76+46 ...... 55+10 361+15 60+20 1440+440 30+1024+6 3+1 3+1 625+100107+35 44+616+8 11+5 400+521248+205300+120 3+2113+5522+8 Pin-on-Disk Endurance Lives Theaverage endurance lifeandvariation foreachcoating indryairandinmoistairisgiveninTable2, andtheaverage isshowninbargraphforminFigure4. Oi Movic Surftech Hohman Teer-Ti CSEM-Ti CSEM-AI TypeofSputtered MoS2Coating Figure4.Average Endurance Lifefordifferent sputtered MoS2films(obtained fromvarious vendors) andtestedinmoistairanddryaironapin-on-disk Tribometer. Ingeneral, mostofthecoatings hadlongerendurance livesindryairthaninmoistair.TheSurftech coating produced equivalent livesinbothatmospheres, butthelivesinbothwereveryshort(-40kc).The Moviccoating hadtheshortest lifeinmoistair(7kc)butalifeof120kcindryair.TheHoman coating had anaverage lifeof76kcinmoistairand100kcindryair,whichwasequivalent totheMoviccoating indry air.TheTeer-Ti coating hadanaverage lifeof55kcinmoistairbutanaverage lifeof361kcindryair. TheCSEM-Ti andCSEM-AL coatings gavelongerlivesinmoistairthatanyoftheothercoatings indry airandwereevenlongerindryair.Fromanendurance pointofviewtheCSEM-Ti andCSEM-AI coatings werefarsuperior totheothersineithermoistordryair,buttheywerealsothethickest. Somediscussion oftheTeer-Ti andCSEM-Ti coatings isappropriate atthispoint.Theprocess for producing sputtered MoS2coatings thatcontain titanium wasinvented byTeerCoatings Limited andthey NASA/CP--2002-211506 309
havethepatentrightstothecoating.CSEMhasobtainedalicensetoalsomakethecoatingusingthe Teerprocess;thereforethetwocoatingsarebasicallyverysimilar.Asfarascouldbeascertained bythe authors,thebasicdifferencebetweenthetwocoatingsisthattheCSEM-Ticoatingcontainsmore titaniumthantheTeer-Ticoating.Inaddition,theCSEM-Ticoatingistwiceasthick. Pin-on-Disk Counterface Wear Thevariation ofweartothecounterfaces (440Cballs)slidingagainst thevarious coatings isgivenin Table2andtheaverage inFigure5.Ingeneral, muchlowerweartothecounterfaces occurred indryair thaninmoistair.Theexception wastheSurftech coating thatproduced lowwearinbothatmospheres, butpartofthatwasduetothefactthatliveswereveryshortandnotmuchactualslidingoccurred. Except fortheHohman coating, thecounterface wearofallcoatings wasequivalent indryair.Theoverallbest combination oflowcounterface wearinbothdryandmoistairoccurred withtheCSEM-Ti coating. 800 OD 700 x600 m500 400 rr300 0_ N200 100 II1 0........... I .......... i.......................................... =DrY-Air .......'.................. ................................. []MoistA!r........ Movic Surftech Hohman Teer-Ti CSEM-Ti CSEM-AI TypeofMoS2Coating Figure5.Average 440Csteelcounterface wearfordifferent sputtered MoS2films(obtained fromvarious vendors) andtestedinmoistairanddryaironapin-on-disk Tribometer. Pin-on-Disk Coating Wear TheTeer-Ti, CSEM-Ti andCSEM-AI coatings werestrongenough tosupport theloadandworegradually awayuntilthesubstrate wasreached. Coating wearratewasnotmeasurable fortheMovic,Surftech and 4000 3500 3000 _2500 o•-_2000X _1500 1000 O  500DryAir#1 DryAir#2 MoistAir#1 MoistAir#2 Sliding Distance (kilocycles) Figure6.Coating Cross-Sectional-Area asafunction ofsliding distance for440Csteelsliding against sputtered CSEM-AI MoS2coatings inmoistairanddryaironapin-on-disk Tribometer. NASA/CP--2002-211506 310
Hohmancoatings,sincethesecoatingswereeithertoosoftortoothintosupportthesliding440Cball counterface. Thesecoatingswerewornawayveryquicklytoathinfilmthatprovidedthelubrication. See Fusaro[21,22]foradiscussiononthemechanisms ofsolidcoatinglubrication. Figure6presentsCross SectionalAreaofthecoatingwearasafunctionofslidingdistanceinkilocyclesfor440Csteelsliding againstsputteredCSEM-AIMoS2coatingsandtestedinmoistairanddryair.Twotestsareshownfor eachcondition.Thefigureshowsthatthewearrateisfairlyreproducible andthatthewearrateisnearly constantindryair.Inmoistair,between50and100kc,therateincreased,butthenwasnearlyconstant. ThevariationofthecoatingwearratesisgiveninTable2andtheaveragesinFigure7forthethree coatingsthatwereabletosupporttheload.Againthedrylairatmosphere providedthelowestwearrates.TheCSEM-Tihadthelowestaveragewearrateof7x10m/m,thenextlowestwastheTeer-Ticoating153 153 (10x10-m/m)followed bytheCSEM-AI coating (14x10-m/m). Itthusappears thattheprimary reasonfortheincreased endurance lifeoftheCSEM-Ti coating compared totheTeer-Ti coating wasdue tothefactthattheCSEMcoating wasmuchthickerandittooklongertowearthrough. Figure7.Average coating wearrateofdifferent sputtered MoS2coatings (obtained fromvarious vendors) andtestedinmoistairanddryaironapin-on-disk Tribometer. Likefrictioncoefficient, endurance lifeandcounterface wear,thecoating wearratewasgreater inmoist airthanindryair.ThelowestwearinmoistairwastheCSEM-Ti coating, whichwas28x10-ism3/m,but wasabout4-times higherthanwhatwasobtained indryair.Theothertwocoatings gave2to3times higherwearratesthantheCSEM-Ti coating inmoistair. Pin-on-Disk Coating Morphology Inaccelerated testing, statistical analysis oftestdatacanprovide numerical comparisons between coatings. Butinordertoobtainamorecomplete understanding ofwhichcoating wouldbebestforyour application, asimpletechnique likeopticalmicroscopy canbeusedtohelpintheevaluation. Todothat, surfaces mustbeevaluated beforefailure.Therefore another reasonforinterval testingistoobserve the rubbing surfaces withanopticalmicroscope tomagnifications ashighas3000X. Figure8showsphotomicrographs oftheMoviccoating weartracksproduced indryairafter23kcof slidingandinmoistairafter2kcofsliding. Darkblisters canbeobserved onthedryairweartrackand darkpowdery thirdbodymaterial (thirdbodymaterial iseitherwearmaterial ordecomposed wear material thatremains onthewearsurfaces) canbefoundinthecenterofthemoistairtrack.Similar surfaces werefoundwiththeSurftech coating. Theseresultsareverysimilartotheresultsofprevious studies thatwereconducted byFusaro[13]onburnished MoS2 filmsthatshowed thattheMoS2 burnished filmoxidized toformMoO3inairandthatthewatervaporintheatmosphere accelerated thisprocess. Figure9givesphotomicrographs oftheweartracksonCSEM-Ti sputtered MoS2coatings testedindryair after660kcofslidingandinmoistairafter160kcofsliding. Bothsurfaces areverysmooth withno indication ofdecomposition ineitheratmosphere unlikeresultsfromtheMovicandSurftech tests.Fine NASA/CP--2002-211506 311
powderydebriscanbeseenoutsideoftheweartrackareas.Inthemoistairtests,therewassomebacktransferred thirdbodymaterialthatmayhavebeenthecauseofthehigherwearinmoistair. Figure10showsahighmagnification photomicrograph ofthesputteredCSEM-TIMoS2 coating after900 kcofslidingshowing anareathathasbeenwornthrough tothesubstrate. Averythinsecondary filmhas formed fromthirdbodymaterial inthisareathathasprevented metal-to-metal contact. Dryair,23kc 20o_m MoistAir,2kc200i_m Figure8.Photomicrographs ofMovieweartracksafter23kcofsliding indryairand2Kcof sliding inmoistaironaPin-on-disk Tribometer. Wear"Track':''_:"" _:!*__" Thirdbodymaterial 200i_m 2.00_m DryAirafter660kc MoistAirafter160kc Figure9.Photomicrographs ofCSEM-Ti MoS2weartracksafter660kcofsliding indryair and160kcofsliding inmoistaironaPin-on-Disk Tribometer. Figure11showsphotomicrographs after650kcofslidingindryairandafter350kcofslidingin moistairofthesputtered CSEM-AI MoS2 coating weartracks.Indryair,asshowninthefigure, thetrackisverysmooth; however thereareareaswherebrittlefracture hasoccurred. Inmoist air,smallsurface pitscanbeseenonthetrack;andinaddition, brittlefracture hasalso occurred butisnotseenintheareashownonthisfigure. Pin-on-Disk Counterface Morphology Transfer filmstothe440Cballcounterfaces occurred formostofthesputtered MoS2coatings thatwereevaluated inthisstudy.Theyweregenerally characterized byabuildup ofmaterial in theinletarea,thinflowing transfer acrossthescarflatandthenpowdery debrisintheexitarea. Figure12showsaphotomicrographs ofthetransfer toa440Cstainless steelballthatslid against aCSEM-AI sputtered MoS2film.Thistypeoftransfer istypicalofmostofthetestsin dryairandmoistaironallthefilms.Therewasoneexception andthatwassputtered CSEM-AI inmoistair.Figure12alsoshowsaphotomicrograph ofthetransfer tothe440Cballthatslid NASA/CP--2002-211506 312
againsttheCSEM-AIMoS2coatinginmoistairafter50kcofsliding.Inthiscase,thereisa smallbuildupofmaterialintheinletareabutaminimalamountoftransfertothescaritself. 100.u.nl Figure 10.Photomicrograph ofCSEM-/i MoS2weartracks after900kcofsliding indryairona Pin-on-Disk Yribometer showing athinareawhere original coating haswornaway.  WearTrack!___ __P__Small surface pitsin _ .... shdlngdirection 50_m 200)_m 650kcinDryAir 350kcinMoistAir Figure11.Photomicrographs ofCSEM-AI MoS2weartracksafter650kcofsliding indryair and350kcofsliding inmoistaironaPin-on-Disk Tribometer. DiskSlidingDirection Heavytransfertoscar lO0_m 935kcofsliding inDryAirDiskSliding Direction 100_m 50kcofsliding inMoistAir Figure12.Photomicrographs ofthewearscarsonthe440Cstainless steelball counterfaces against CSEM-AI sputtered MoS_coatings onaPin-on-Disk Tribometer. NASA/CP--2002-211506 313
BlockonRin.qFriction Coefficient Theaverage steady-state frictioncoefficients forthetestsconducted indrynitrogen ontheBlock-on-Ring Tribometer testsaregiveninTable3andalsoinFigure13.Inaddition tonon-coated blocks, afewtests werealsoconducted withcoated blocks. Ingeneral frictioncoefficients werelowerindrynitrogen onthe Block-on-Ring Tribometer thanthoseobtained indryormoistairwiththePin-on-Disk Tribometer. The MovicandHohman coatings gavethelowestfrictioncoefficients of0.01.Thevaluesfoundfortheother coatings were:CSEM-Ti, 0.02,Teer-Ti, 0.03,Surftech, 0.04andCSEM-AI, 0.07.Thecoated blocks slidingonthecoated ringsdidnotchange thesteady-state valueofthefrictioncoefficients obtained as compared tothenon-coated blocks. Block-on RingEndurance lives Thevariation ofcoating endurance livesforthetestsconducted ontheBlock-on-Ring Tribometer are giveninTable3andtheaverages aregiveninFigure14.Thelongest endurance lifefortheBlock-onRingTribometer testswereobtained withtheHohman MoS2coating, although therewasconsiderable variation. Thelongest average lifewasobtained fortheCSEM-Ti coating testedagainst aCSEM-Ti coatedblock.Acoatedblockversusanuncoated blockincreased theaverage lifeoftheCSEM-Ti coating from323kcto6132kc.TheTeer-Ti sputtered MoS2coating gaveanaverage lifeof303kcwhichwas verysimilartothatfoundfortheCSEM-Ti coating against theuncoated block.TheMoviccoating sliding against anon-coated blockgavealifeof1165kc,butthelifeslidingagainst acoated CSEM-Ti block decreased to360kc.TheCSEM-AI coating lubricated verypoorlyinnitrogen. Theuncoated blockgavea lifeof0.3kcandwhenitwasslidagainst theblockcoated withCSEM-AI, itfailedimmediately. The Surftech coating alsolubricated poorlyinnitrogen andfailedafter0.6kcofsliding. Table3"Block-on-Rinq TestResults MoS2 CoatingAverage Friction Coefficient Non-Coated Block Movic 0.01 Surftech 0.04 Hohman 0.01 Teer-Ti CSEM-Ti0.03 0.02 CSEM-AI 0.07Coated Block 0.01 0.02 FailedEndurance Life (Kilocvcles) Non-Coated Block 1166+45 0.6+0.4 5556+3570 303+110 323+321 0.3+0.1Coated Block 360+70 6132+950 FailedBlockWearRate (maimx1018) Non-Coated Block 2+0.5 1.2+1.0 9.5+7.0 24,000+23,955Coated Block 190+160 0.7+0.3 Failed 0.08 '4"0.07t- •_0.06 '_-0.05 O t,_0.04 ¢.. O0.03 .0--' 00.02 LU..0.01 0 Movic[]Noncoated Block ;E_Coated Block Surftech Hohman Teer-Ti TypeofSputtered MoS2CoatingCSEM-Ti CSEM-AI Figure13.Average friction coefficient fordifferent sputtered MoS2films(obtained from various vendors) andtestedindrynitrogen onablock-on-ring Tribometer. NASA/CP--2002-211506 314