Rolling contact fatigue performance of plasma sprayed coatings

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1、WEARELSEV!ERWear220(i(~8)80-91RollingcontactfatigueperformanceofplasmasprayedcoatingsR.Ahmed~'*,M.Hadfieldh'CambridgeUniversity.Depart#ne~t~fEngim'ering,Trm.pingtonStreet,Cambridge.CB2IPZ,UK~BournemouthUniver.ri~'.DeportmentofProduceDesignandMamqfacttlre.Trihol¢~gyl)csignResearchUnit.Boterne

2、mouth.BHI3NA.UKReceived18December1997:acceptedlMay1998Ahstrat'tThisexperimentalstudyde,~ribestheRollingContactFatigueIRCF)performanceandthefailuremechanismsofplasmasprayedtungstencarbidecobalt(WC-15%Co)coatings.Theadvancementsofplasmaspraycoatingsduetohighervelocityandtemperatureoftheimpacti

3、nglamellacallforinvestigationsintonewapplications.Onepossibleapplicationistherollingelementbearing.Amodifiedfourballmachinewhichmodelstheconfigurationofadeepgrooverollingelementballbearingwasusedasanacceleratedmethodtocomparetheroilingcontactfatigueresistanceofthetestmaterials.RCFtestswereco

4、nductedinconventionalrollingelementsteelballbearing(steellowerballs)andhybridceramicbearing(ceramiclowerballs)contactconfigurations.Plasmasprayedcoatingsweredepositedonabearingsteel(440-C)substrateatdifferentthicknes~s.Thecoatedrollingelementconesweregroundandpolishedtoachieveag~dsurfacefini

5、shontherollingelements.RCFtestswereconductedunderthevarioustribologicalconditionsofcontactstress,lubricantandtestconfigurations.ThefrictionaltorqueinthecupassemblywasmeasuredduringtheRCFtestswiththeaidofaforcetransducer.Thespeedoftheplanetaryballswasmonitoredusinganaccelerometerandfastfourie

6、rtransf0rmatinnofthevibrationsignal.Thisenabledtheexperimentalmeasurementofslidingbetweenthecoatedconeandthedrivenballs.Thefailedrollingelements,coatingdebrisandthelowerplanetaryballswereanalyzedforsurfaceobservationsundertheScanningElectronMicroscopetSEM),andElectroProbeMicroscopeAnalysis(E

7、PMA).ThetestresultsindicatethatthecoatingperformancewasdependentUl~mthetriblrlogicalconditionsduringthetest.Thefailuremodeswereobservedtobesurfacewearandthecoatingdelamination.©1998F.IsevierScienceS.A.Allrightsreserved.Ke)lwords;Rollingcontactfalig