Table Of ContentMichael 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
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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
