surface hardening of austenitic fe–cr–ni alloys for accident-tolerant nuclear fuel cladding

155 Pages·2017·3.92 MB·English

SURFACEHARDENINGOFAUSTENITICFE–CR–NIALLOYSFOR
ACCIDENT-TOLERANTNUCLEARFUELCLADDING
by
ZHENLI
Submittedinpartialfulfillmentoftherequirements
ForthedegreeofDoctorofPhilosophy
DepartmentofMaterialsScienceandEngineering
CASEWESTERNRESERVEUNIVERSITY
January,2018
SurfaceHardeningofAusteniticFe–Cr–NiAlloysForAccident-Tolerant
NuclearFuelCladding
CaseWesternReserveUniversity
CaseSchoolofGraduateStudies
Weherebyapprovethethesis1of
ZHENLI
forthedegreeof
DoctorofPhilosophy
Dr.FrankErnst 04/26/2017
CommitteeChair,Adviser Date
DepartmentofMaterialsScienceandEngineering,CWRU
Dr.ArthurHeuer 04/26/2017
CommitteeMember Date
DepartmentofMaterialsScienceandEngineering,CWRU
Dr.JohnLewandowski 04/26/2017
CommitteeMember Date
DepartmentofMaterialsScienceandEngineering,CWRU
Dr.SunnivaCollins 04/26/2017
CommitteeMember Date
DepartmentofMechanicalandAerospaceEngineering,CWRU
Dr.ScottLillard 04/26/2017
CommitteeMember Date
DepartmentofChemicalandBiomolecularEngineering,TheUniversityofAkron
1Wecertifythatwrittenapprovalhasbeenobtainedforanyproprietarymaterialcontainedtherein.
DedicatedtomywifeXunZhan,mydaughtersMacieLi,JoannaLi,my
parentsLimingLi,YingnanFanandparentsinlawZhijunZhan,Liping
Gaowithlove
Table of Contents
ListofTables vi
ListofFigures vii
Acknowledgements xv
Acknowledgements xv
Abstract xvi
Abstract xvi
Chapter1. Introduction 1
Motivation 1
MaterialsCandidate 2
ColossalSuper-saturationEngineering 8
Approach 15
Chapter2. Experimental 19
AAA(aqueousacidactivation) 20
GasPhaseProcessing 21
Characterization of CSS (colossal super-saturation)-Engineered Near-surface
Region 25
PropertiesofCSS-engineeredNear-surfaceDiffusionZone 27
OxidizedandIrradiatedLTC/LTNCNear-surfaceRegionCharacterization 31
Chapter3. Results 33
LTC/LTNCNear-surfaceRegionCharacterization 33
iv
PropertiesofLTC(low-temperaturecarburization)andLTNC(low-temperature
nitro-carburization)Layers 53
Chapter4. Discussion 86
PossibleMechanismsofPassivationbyEthanol 86
CSS-engineeringofAISI-316L,AL-6XNandIN-718 89
OxidationTests 104
SCC(stresscorrosioncracking) 110
IrradiationTest 115
Chapter5. Conclusions 117
Chapter6. Futurework 120
AppendixA. AqueousAcidActivation 122
AppendixB. LongtermannealingofcarburizedAISI-316L 126
AppendixC. LTC(low-temperaturecarburization)ofnanostructuredAISI-316L 129
Appendix. CompleteReferences 132
v
List of Tables
1.1 Mainchemicalcompositions(>1.0at%)ofAISI-316LSS,AL-6XN,and
IN-718. Theunitofatomicconcentrationisat.%. 16
2.1 AISI-316LsamplespreparationparametersbeforeXPS. 21
2.2 ShapesanddimensionsofAISI-316L,AL-6XN,andIN-718samples. 22
2.3 Gasflowratesduringactivationandcarburizationprocess. 24
2.4 Gasflowratesduringnitro-carburizationofIN-718. 25
2.5 PostCSS-engineeringheatexposure 30
B.1 Carbonprofileintegrationratiobetweenas-carburized,air-annealed
andvacuum-annealedAISI-316Lspecimens. 127
vi
List of Figures
1.1 Optical micrographs of cross sections of Zircaloy-2 and AISI-317L
after 28.8ks exposure to 1MPa steam at 1070K, 1270K, 1470K,
respectively. (a)-(c)Zircaloy-2. (d)-(f)AISI-317L. 3
1.2 (a)Vickershardness(triangles)andcarbonconcentration(circles)
depthprofiles. (b)Residualstressprofileofcarburized316Lstainless
steel. 5
1.3 Potentiodynamicpolarizationcurvesofcarburizedandas-received
AISI-316L, recorded in sea-water-like electrolyte (0.6M NaCl
solution). 6
1.4 TTTdiagramsofanAISI-316austeniticSSwithtwodifferentatom
fractionsX ofcarbon. 7
C
1.5 (a)J4915furnace. (b)MainchamberofJ4915furnace. 10
1.6 GasphaseLTCorLTNCprocess. 11
1.7 Metallographicimageofgasphase(C H )LTCofelectro-polished
2 2
AISI-316L. 12
1.8 Schematicstructureofaplasmaunit. 13
1.9 Schematicprocessofampoulemethodfornitro-carburization. 14
2.1 LTC(low-temperaturecarburization)recipesofAISI-316L,AL-6XN,
andIN-718. 23
2.2 Typical nano-indentation setting for hardness depth profile of
CSS-engineeredFe–Cr–Nialloys. Theblacktrianglesareindentations. 27
vii
2.3 SchematicdiagramofpininsertedintotheendsofAISI-316Ltube. 28
2.4 Dpadepthprofileof1.5MeVprotonsintoironsimulatedbySRIM. 31
3.1 XRD patterns of non-treated and carburized AISI-316L tubes and
coupons. 33
3.2 XRDpatternsofnon-treatedandcarburizedAL-6XN. 34
3.3 XRD patterns of non-treated, carburized, and nitro-carburized
IN-718. 35
3.4 Metallographic cross-sections of (a) carburized AISI-316L,
(b) carburized AL-6XN, (c) carburized IN-718, and (d) nitro-
carburizedcoupons,respectively. 37
3.5 Metallographic cross-sections of carburized AL-6XN for different
surfacefinishingandactivation: (a), (c), (e), (g)are polishingwith
P180,P800,P4000,andelectro-polishing,respectively. (b),(d),(f),(h)
arepolishingwiththecorrespondingSiCgritpapersandactivating
withaqueousHClatroomtemperaturefor300s,respectively. 38
3.6 Metallographiccross-sectionsofLTC(low-temperaturecarburization)
AND LTNC (low-temperature nitro-carburization) Fe–Cr–Ni alloy
tubes. (a)RegionsawayfromthetwoendsoftheLTCAISI-316Ltube.
(b)AtypicalimageoftwoendsoftheLTCAISI-316Ltube. (c)Regions
awayfromthetwoendsoftheLTCIN-718tube. (d)Atypicalimage
oftwoendsoftheLTCIN-718tube. (e)Regionsawayfromthetwo
endsoftheLTNCAISI-316Ltube. (f)Atypicalimageoftwoendsof
theLTNCAISI-316Ltube. 40
viii
3.7 (a)SchematicdiagramofgasflowthroughtheAISI-316Ltube. (b)
PartofCVDfurnacewithdiameter2RandlengthL.(Prof. F.Ernst,
unpublished) 42
3.8 (a) Increasing gas-flow through the tube by usinga funnel. (b) An
optical image of a cross-section of a carburized AISI-316L tube by
usingthefunnel. 45
3.9 Metallographiccross-sectionofIN-718tubeafterroom-temperature
aqueous HCl activation and LTNC (low-temperature nitro-
carburization). 46
3.10 MetallicsignalsacquiredbyXPS(X-rayphotoelectronspectroscopy). 48
3.11 XPS (X-ray photoelectron spectroscopy) data collected from the
activatedsurfaceofAISI-316L:(a)immersedinethanolfor300safter
AAA(aqueousacidactivation)and(b)immersedindeionizedwater
for300safterAAA. 49
3.12 SAM(scanningAugermicroprobe)elementalconcentrationdepth
profilesof(a)AISI-316LafterLTC,(b)AL-6XNafterLTC,(C)IN-718
afterLTC,and(d)IN-718afterLTNC,respectively. 50
3.13 SAM(scanningAugermicroprobe)Crconcentrationdepthprofiles
ofIN-718afterLTC,LTNC,andannealingatcarburizationornitro-
carburizationtemperatureunder0.1MPaN condition,respectively. 51
2
3.14 Nano-hardnessdepthprofilesof(a)AISI-316LafterLTC,(b)IN-718
afterLTC,and(c)IN-718afterLTNC,respectively. 54
ix
3.15 Tensile tests of (a) Non-treated, annealed at carburization
temperature (720K) for 72ks (20h), and carburized AISI-316L
tubes, (b) Non-treated, annealed at carburization temperature for
100.8ks(28h),carburizedandnitro-carburizedIN-718tubes. 55
3.16 Weartrenchprofilesof(a)non-treatedand(b)carburizedAISI-316L
coupons. 57
3.17 MFM (magnetic force microscopy) data of (a) and (b) carburized
IN-718,(c)and(d)nitro-carburizedIN-718. 58
3.18 X-ray diffractograms of (a) carburized AISI-316L, (b) carburized
AL-6XN, (c) carburized IN-718, and (d) nitro-carburized IN-718,
respectively,beforeandafterPCHE-A-Air. 60
3.19 Metallographic cross-sections of (a) carburized AISI-316L,
(b) carburized AL-6XN, (c) carburized IN-718, and (d) nitro-
carburizedIN-718,respectively,beforeandafterPCHE-A-Air. 61
3.20 SAM (scanning Auger microprobe) elemental concentration
depth profiles of (a) carburized AISI-316L, (b) carburized AL-6XN,
(c)carburizedIN-718,and(d)nitro-carburizedIN-718,respectively,
beforeandafterPCHE-A-Air. 63
3.21 Nano-hardness depth profiles of (a) carburized AISI-316L,
(b) carburized AL-6XN, and (c) carburized IN-718, respectively,
beforeandafterPCHE-A-Air. 64
x