Michael Danyluk · Anoop Dhingra Rolling Contact Fatigue in a Vacuum Test Equipment and Coating Analysis Rolling Contact Fatigue in a Vacuum Michael Danyluk (cid:129) Anoop Dhingra Rolling Contact Fatigue in a Vacuum Test Equipment and Coating Analysis MichaelDanyluk AnoopDhingra GEHealthcare DepartmentofMechanicalEngineering Milwaukee,WI,USA UniversityofWisconsin Milwaukee,WI,USA ISBN978-3-319-11929-8 ISBN978-3-319-11930-4(eBook) DOI10.1007/978-3-319-11930-4 SpringerChamHeidelbergNewYorkDordrechtLondon LibraryofCongressControlNumber:2014953303 ©SpringerInternationalPublishingSwitzerland2015 Thisworkissubjecttocopyright.AllrightsarereservedbythePublisher,whetherthewholeorpart of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation,broadcasting,reproductiononmicrofilmsorinanyotherphysicalway,andtransmissionor informationstorageandretrieval,electronicadaptation,computersoftware,orbysimilarordissimilar methodologynowknownorhereafterdeveloped.Exemptedfromthislegalreservationarebriefexcerpts inconnectionwithreviewsorscholarlyanalysisormaterialsuppliedspecificallyforthepurposeofbeing enteredandexecutedonacomputersystem,forexclusiveusebythepurchaserofthework.Duplication ofthispublicationorpartsthereofispermittedonlyundertheprovisionsoftheCopyrightLawofthe Publisher’s location, in its current version, and permission for use must always be obtained from Springer.PermissionsforusemaybeobtainedthroughRightsLinkattheCopyrightClearanceCenter. ViolationsareliabletoprosecutionundertherespectiveCopyrightLaw. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publicationdoesnotimply,evenintheabsenceofaspecificstatement,thatsuchnamesareexempt fromtherelevantprotectivelawsandregulationsandthereforefreeforgeneraluse. While the advice and information in this book are believed to be true and accurate at the date of publication,neithertheauthorsnortheeditorsnorthepublishercanacceptanylegalresponsibilityfor anyerrorsoromissionsthatmaybemade.Thepublishermakesnowarranty,expressorimplied,with respecttothematerialcontainedherein. Printedonacid-freepaper SpringerispartofSpringerScience+BusinessMedia(www.springer.com) Preface The motivation to write this monograph was to share engineering experiences related to thin film testing and vacuum systems. Testing of thin film lubricants applied to ball bearings that are used in rotating systems in high-voltage vacuum deviceshasreceivedlittleattentioninrecentdecades.Thismonographhasenabled us to share a unique combination of engineering experiences needed to solve practical problems related to testing of thin film systems. Design and mechanical testing involving vacuum chambers, pumps, plasmas, and the instrumentation needed to operate these has brought to light some less well known combinations ofmechanicsandphysicsneededtomeetspecifictestingneeds.Indeed,solutionsto mechanical engineering problems require creative, cost effective, and innovative combinationsofideasandequipmenttoachievesustainableandpracticalsolutions. Necessity is the mother of invention, and this is certainly true when applied to mechanicaltestinginthecontextofmanufacturingproblems. The impetus behind this monograph is that tribology testing in vacuum in the rangeof10(cid:1)5to10(cid:1)8Torrwasrequiredtomeetaspecifictestingneed.Thinsolid filmlubricationhasbeenusedextensivelyinrotatinganodex-raytubeapplications. A non-volatile, carbon-free lubrication, such as silver or nickel-copper-silver, is usedtolubricatebearingpartsduringoperationinhighvacuumandinthepresence ofveryhighvoltages,upto140,000V.Rotatingelementbearingsthatareusedin x-raytubesareasealed lubrication system,thatis, lubrication is added atbearing assembly and the system operates as a closed system for the remainder ofits life. Thegoaltofurtherunderstandsolidlubricationfilmsappliedtoballbearingswasa financial decision to reduce overall cost and extend bearing life. For example, improving film adhesion will help reduce infantile factory failures. Optimizing film thickness will extend ball-bearing life, and thereby extend the life of the x-ray tube for the customer. However, if the film is too thick it may flake off leading to catastrophic bearing failure. Choice of lubrication is key to prevent interactionwith the fragile electronics inside the x-tube. Forexample,solidlubri- cantssuchassilverandgoldarestableinsidethex-raytubeenvironmentandwill notinteractwithelectronbeamcomponentsduringoperation.Improvementsinfilm v vi Preface adhesion,depositiontechniques,andthicknesscontroloccurredinorderofpriority toaddthemostvaluetothecustomerintheshortestpossibletime. The acquired knowledge shared throughout this monograph has been put into practicetocorrectengineeringproblemsthatreducex-raytubebearinglife,andto deliver the highest value for the customer. The monograph organization has been dictatedbynecessitytoimproveball-bearingsystemlife.Thestepstotestthinfilms in rolling contact fatigue under vacuum conditions are outlined in the book. Pro- cedures to prevent contamination and corrupt results are explained to help the reader understand the level of cleanliness required when testing hardware that will be used in a high-voltage and high-vacuum device. Our goal is to discuss andsharewiththereaderissuesandproblemsthatmaybeencounteredconcerning bearingtestinginhighvacuum. Thebookmaybeusedbystudentsandengineersforguidancetobuild,test,and commission any vacuum chamber application. Best practices that reduce risk of contaminationaswellasreduceoperatingcostsarepresentedinChap.2.Diagnos- tic tools that can detect very slow leaks and that can beused toquantify chamber vacuum integrity are presented in this chapter as well. Within a manufacturing setting,oneisoftenpressuredtoputanewlyconstructedvacuumsystemintouseas soon as possible after it is built. However, without proper system commissioning andcharacterization,thedatafromthenewmachinemaybecorruptfromthevery beginning. Time is wasted to either explain anomalies caused by the system or to reproduceallresultsduetosuspecttestchamberbehavior. Thisbookissuitedforalllevelsofexpertiseofscientistsandengineers,aswell as graduate students in the mechanical and electrical sciences. We start with a general discussion about chamber design, vacuum pumps, andvacuum diagnostic tools. While there are many vacuum-system design books available, in the litera- ture; our goal is to help tailor the vacuum system for testing coatings in rolling contact fatigue (RCF) at high speed and vacuum conditions. We continue in Chaps. 3 and 4 with examples of RCF testing with emphasis on thin film silver lubricationappliedtoballbearingsteelandsilicon-nitriderotatingparts.Adetailed discussion about the physical vapor deposition ion-plating method is presented in Chap. 6. The ion plating method is well suited for coating a large number of ball bearings at one time with minimal risk of contamination. We use SimulinkTM to model and control an ion plating process since is it is readily available to both studentsandprofessionalsalike. Asurveyofthecurrentliteraturerevealsthatthereislittleresearchconcerning process aberration and RCF life. In this book, we use the rolling contact fatigue method to quantify the effects of process aberration on coating life. A discussion aboutdc-plasmasandtheireffectsoncoatingperformanceispresentedinChap.7. Plasmas are difficult to understand, and there are several text books available concerning the theory and application of plasmas for thin film deposition. We start with practical calculations, such as Debye length and mean-free-path, to help the reader to quantify the plasma related to their process. Our goal is for the readertounderstandtheplasmaasamanufacturingtoolusingsystemlevelinputs suchasprocesspressureandvoltage. Preface vii In Chaps. 6, 8, and 9, we include a discussion about process control and disturbancerejection.Perhapsmoreimportanttoaprocessengineerthanascientist or student, disturbance rejection enables consistent manufacturing coating quality and gives the manufacturing engineer a frame work from which to quantify the effects of process aberration. It is a given that disturbances and even process mistakes will occur in manufacturing coating processes. Choosing the optimal control scheme can help mitigate the effects of unpredictable disturbances on the coatingprocess. Thereaderofthisbookisencouragedtoseekoutandreadfurtherthereferences citedwithinthetext.Throughoutthisbook,itwasourgoaltobringtogetherunique combinations of previous engineering work. Rolling contact fatigue testing in vacuum andat high speed isonesuch example.Upon reading this book,we hope thatthereaderwillbeinspiredtobringtogetherothersuchuniquecombinationsof engineeringworktohelpsolveproblemsinengineeringandmanufacturing. TheauthorswouldliketogratefullyacknowledgeGeneralElectricHealthCare for allowing some of this testing at their facility in Milwaukee, Wisconsin. We would like to thank the University of Wisconsin-Milwaukee for use of its computingandlaboratoryresourcesbetweenFall2010andSpring2014. Milwaukee,WI,USA MichaelDanyluk AnoopDhingra Contents 1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1 CoatingProcessesCompatiblewithHigh-VoltageDevices. . . . . . 2 1.2 MonographOverview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.3 PlasmaDiagnosticsandMeasurements. . . . . . . . . . . . . . . . . . . . 4 1.4 ProcessControlConsiderations. . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.5 MonographOrganization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 PartI VacuumSystemsInfrastructureandChamberDesign. . . . . . . 7 2 VacuumChamberDesign. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.2 VacuumChamberDesignConsiderations. . . . . . . . . . . . . . . . . . 10 2.3 ChamberMaterialSelection. . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2.3.1 MaterialOutgassing. .. . . . . .. . . . .. . . . .. . . . .. . . . .. 13 2.3.2 VacuumWelds,Gaskets,andAttachments. . . . . . . . . . . . 14 2.3.3 VacuumChamberIsolation. . . . . . . . . . . . . . . . . . . . . . . 14 2.4 VacuumComponentsSelection. . . . . . . . . . . . . . . . . . . . . . . . . . 15 2.4.1 High-VacuumPumpingSystem. . . . . . . . . . . . . . . . . . . . 15 2.4.2 VacuumMeasurementSystemSelection. . . . . . . . . . . . . . 15 2.4.3 VacuumSystemSafetyInterlocks. . . . . . . . . . . . . . . . . . 16 2.5 CaseStudy:ChamberVibrationIsolationandMeasurement. . . . . 17 2.5.1 VibrationTransmissibilityDesign. . . . . . . . . . . . . . . . . . 17 2.5.2 AccelerometerResponseComparison. . . . . . . . . . . . . . . . 21 2.6 CaseStudyContinued:OptimumChamberDesign. . . . . . . . . . . . 24 2.6.1 DesignOptimizationAnalysis. . . . . . . . . . . . . . . . . . . . . 25 2.6.2 CompareOptimumDesigns. . . . . . . . . . . . . . . . . . . . . . . 30 2.7 AssemblyandCleaning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 ix