AGMA 98FTM8-1998

Irì98FïM8NewTestMethodsfortheEvaluationofWear,ScuffingandPittingCapacityofGearLubricantsby:B.-R.Höhn,P.Oster,K.Michaelis,GearResearchCentre(FZG),GermanyAmericanTECHNICALPAPERCOPYRIGHTAmericanGearManufacturersAssociation,Inc.LicensedbyInformationHandlingServicesCOPYRIGHTAmericanGearManufacturersAssociation,Inc.LicensedbyInformationHandlingServicesNewTestMethodsfortheEvaluationofWear,ScuffingandPitting.CapacityofGearLubricantsB.-R.Höhn,P.Oster,K.Michaelis,GearResearchCentre(FZG),Germany[ThestatementsandopinionscontainedhereinarethoseoftheauthorandshouldnotbeconstruedasanofficialactionoropinionoftheAmericanGearManufacturersAssociation.]AbstractFormaximumenergysavingslowviscositylubricantsarefrequentlyused.Increasingtransmittedpowerleadstohighertemperaturesandthusthinnerlubricatingfilms.Thesetendenciesincreasethefailureprobabilityingearcontactswithrespecttowear,scuffing,micropittingandpittingperformance.NewtestmethodsonmodifiedFZGgeartestrigsweredevelopedtoevaluatetheloadcarryingcapabilityofgearlubricants.ForthelowspeedregimeaweartestusingC-typegearsatlowpitchlinevelocityof0.05m/s,andtwodifferenttemperaturesof90and120Ctoconsiderdifferentadditiveresponseathighloadingofloadstage12(C/0.05/90:120/12)wasdevelopedandappliedtomanydifferentlubricants.NewscuffingproceduresforgearlubricantsofscuffingperformancebetweenAPIGL3andGL5weredeveloped.ThesteptestA10/16.6R/90usesA-typegearsof10mmpinionfacewidthat16.6m/spitchlinevelocitywithadrivenpinion.AdiscriminationofallgearoilsuptothelevelofAPIGL4ispossible.AshocktestS-A10/16.6R/90withdirectloadingintheexpectedloadstagediscriminatesbetweenGL4andGL5lubricants.DifferentstandardpittingtestsareavailablefordifferentlubricantviscositygradesusingC-typegearsat8.3m/spitchlinevelocityand90Cinloadstages9(PTC/9/90)or10(PTC/10/90).Forautomotiveapplicationsloadspectrumtestingispossibleatlow(PTC/LLS/90)andhigh(FTC/HLs/90)loads.Forapplicationswithlongoildrainintervalsacombinedpittingandoilageingtestwasdeveloped(PITSCi85TS)usingC-typegearsatvariableload,speedandtemperatureconditions.Athightemperatureconditionsbetween120and150Ctheoilageingpropertiestogetherwiththeirinfluenceonpittingcharacteristicsisevaluatedincorrelationtoareferenceoil.Thetestmethodsaredescribed.Testresultswithdifferentmarketproductsarediscussed.CopyrightO1998AmericanGearManufacturersAssociation1500KingStreet,Suite201Alexandria,Virginia,22314October,1998ISBN:1-55589-726-6COPYRIGHTAmericanGearManufacturersAssociation,Inc.LicensedbyInformationHandlingServicesCOPYRIGHTAmericanGearManufacturersAssociation,Inc.LicensedbyInformationHandlingServices..PNEWTESTMETHODSFORTHEEVALUATIONOFWEAR,SCUFFING,ANDPITTINGCAPACITYOFGEARLUBRICANTSB.-R.Höhn,P.Oster,K.MichaelisGearResearchCentre(FZGI,Germany1IntroductionThelubricantasadesignelementcanplayanimportantroleintheslowspeedwear,scuffing,micro-pittingandpittingbehaviorofgearsinpowertrains.Withthedemandofextendedoildrainintervals,pre-dominantlyinautomotiveapplications,notonlytheJerformanceofthenewoilbutalsothatofusedoilswiththermalandoxidativedegradationhastobeob-served.Baseoiltype,viscosityandadditivesysteminfluencethedifferentfailuremodes.Comprehensiveknowledgeofthelubricantperformanceundercompa-rabletestconditionsisthekeyfactorforlubricantoptimizationfortransmissionsinpractice.a*AnumberoftestmethodswasdevelopedusingtheFZGback-to-backgeartestrigwhereover500machinesareavailableworld-wide.Thesemeth-odsaretheChevronweartestA/0.57/120/10fortractorhydraulicfluids[II,thescuffingtestA/8.3/90[2,31,themicropittingtestGFC/8.3/90[41forindus-trialgearoils,andthepittingtestPTC/9:10/90[51forautomotivegearoils(seeTable1).Continuousoildevelopment,costreductionandnewmarketdemandsmadeitnecessarytodevelopnewtestmethodsforgearoils.ThesenewmethodsontheFZGgeartestrigarepresentedanddiscussed.2GeneralConsiderationsonTestStrategiesThebesttestconfigurationforfullcomparabili-tyistheactualgearboxundertypicaloperatingcondi--ions.Forindustrialgearapplicationsthisisalwaystooaexpensiveandforautomotivegearapplicationsthisismostlytootimeconsuming.Thesecondbestaretestproceduresusingdefinedtestgearswithhighreproducibilityingeome-try,heattreatmentandsurfacefinishbeingexposedtoexaggeratedoperatingconditionsinordertoreducetesttime.Parameterswhicharemodifiedversusoper-atingconditionshavetobechosenverycarefullyforbestsimulation.TestGearsHighreproducibilityoftestgearscanonlybeachievedwhenonemanufacturerproducessuchgearsonthebasisofacommercialinterest.Exotictestgearswhereonly200pairsareorderedeverythreeyears,canhardlybeproducedtotherequiredhighqualitystandard.Therefore,itishighlyrecommendedtowriteanewtestprocedurearoundalreadyexistingtestgears,ase.g.FZGstandardtestgeartypesAandC(seeTable2).TheproductionfiguresofFZGstandardtestgearstypeAareintherangeofsome2000peryearandtypeCintherangeofsome500peryear.ThemanufacturerofthesegearshasdedicatedthreegrindingmachinesonlyforthefinishingofAtypegears.TogetherwiththecontrolintheCECprojectgroupST007,dealingwiththescuffingtest,acontin-uouslyhighaccuracyandreproducibilityofthetestgearscanbeguarantee