Heat treatment optimization of high alloy steel castings and welds

123 Pages·2015·3.88 MB·English

by  Jeffrey D. Farren

Lehigh University
Lehigh Preserve
Theses and Dissertations
2007
Heat treatment optimization of high alloy steel
castings and welds
Jeffrey D. Farren
Lehigh University
Follow this and additional works at:http://preserve.lehigh.edu/etd
Recommended Citation
Farren, Jeffrey D., "Heat treatment optimization of high alloy steel castings and welds" (2007).Theses and Dissertations.Paper 985.
This Thesis is brought to you for free and open access by Lehigh Preserve. It has been accepted for inclusion in Theses and Dissertations by an
authorized administrator of Lehigh Preserve. For more information, please [email protected].
Farren, Jeffrey D.
" .
Heat Treatment
Optimization of
High Alloy Stainless
.Steel Castings arid
Welds
-
..t"... 'l .~. 4' ' •
January 2008·
Heat Treatment Optimization
ofHigh Alloy Stainless Steel
Castings- and Welds
By
Jeffrey D. Farren
J
Presented to the Graduate and Research Committee
ofLehigh University
in Candidacy for the Degree of
Master's ofScience
In
Materials Science and Engineering
Lehigh University
October 7, 2007

Acknowledgments
0-
Iwould liketothankthe manypeoplethat helped me overthe years and made
this workpossible. First and foremost, Iwanttooffer my sincerestthanksto my
\
advisor, Prof. JohnDuPont, who has taughtme so much aboutthefield ofmetallurgy.
You have guidedmeto becomethe materials scientistthatI amtoday and I look
forward to continuing my professional and personal growth as I continue my PhD
work. Iwould also liketo thankProf. Arnold Marderwho has impartedmany
technical and personalwordsofwisdom andtaughtme aboutthe C-curve oflife.
•
Manythanks must also be givento theLehighUniversity support staff, who have been
instrumental inhelping meto complete my experimental program. ArlanBenscoter
has played avital role in allthings lightoptical and metallographic; MikeRexand
John Gregoris have prepared COUNTLESS samples for my experiments; and Dave
Ackland has sharedhis significantknowledge about electronmicroscopy. All ofmy
colleagues intheEngineeringMetallurgy Group must also be acknowledged. I
appreciate all ofthetimethat each ofyou has spentcritiquingpresentations and
discussing ideas.
Iwould also liketo acknowledgetheUnited StatesDepartmentofEnergy and
the SteelFounder's SocietyofAmericafor fundingthis research. Specialthanks are
owedto MalcolmBlairandRonBirdfor lendingtheirtime andtalents to help guide
my researchinthe right direction. I canonly hopethatthe results ofthis research
benefitthe SFSAas much~s youbothhave helped me.
_III
Finally, Iwould liketothank my family, who have made me thepersonthatI
amtoday and have made all ofthis possible. Tomy wifeMonica, Ithank you so
muchfor puttingup with me (and continuingto do so) duringthe arduousgraduate
schoolprocess. You arethebestthingthat everhappened to me and I love you. To
Mom and Dad, Iwill be forever grateful for each and every sacrifice you madewhile
raising me and sending me to college. Iloveboth ofyou so much and IhopethatI
continueto make you proud. Finally, Iwould liketothankmy sister, Jennifer. Iam
forever grateful forthe examplethatyou setfor me. Your success and dedication
have motivatedmeto becomethe personthat Iam today.
0-
IV
Table ofContents
List ofTables vi
ListofFigures vii
' fF' ..
L1st 19ures
0 VB
Abstract 1
1. Introduction 2
1.1 Corrosion TestPractices 2
ASTMG48-03'-Methods A& E 3
ASTME 1169- 02: Standard Guidefor Conducting'Ruggedness Tests 4
Influence ofTestVariables onTestResults 4
1.2HeatTreatmentOptimizationofCN3MN and CK3MCuN 10
.MicrostructuralDevelopment 10
HomogenizationHeat Treatment 14
DissolutionKinetics 18
1.3 Research Objectives 20
2. Materials 22
3. ExperimentalProcedure , 23
3.1 CorrosionTestPractices ~ ; 23
ASTMG48 Corrosion TestingUsing ASTME 1169 23
3.2HeatTreatment OptimizationofCN3MN and CK3MCuN : 25
MicroporosityCalculations andMacrosegregationMeasurements 25
SamplePreparationandHeatTreatment 25
Microstructural Characterization 26
ASTMG48ACorrosion Testing ofHeat Treated Samples 28
4. Results and Discussion 29
4.1 CorrosionTestPractices : 29
ASTMG48E:.: 29
ASTMG48A : 31
4.2 HeatTreatment OptimizationofCN3MNand CK3MCuN 32
MicroporosityandMacrosegregationResults 32
As-CastMicr,ostructures : 33
SigmaPhaseDissolutionKinetics 35
HomogenizationKinetics andResidual Segregation 37
CorrosionResistance ofHeat Treated~lloys 41
5. Conclusions 43
5.1 CorrosionTestPractices 43
5.2 HeatTreatment and CorrosionResistance ofCN3MN and CK3MCuN 44
6. AppendixI 88
7. ReferenceList 98
Curriculum Vita..................................................................................................... 101
v
List ofTables
TableI -EffectofTemperature onTimeto BreakdownUsing aLarge Crevice
Assembly 46
TableII -List ofparameters usedinalphacalculation 46
m.
Table List ofparametersused to calculatethe sigmavolume fraction expected
after 1150°C and 1205°Cheattreatments inalloy CN3MN and CK3MCuN 46
TableIV -Chemical composition(inwt %) ofcast and wrought2205 duplex stainless
steel. 46
Table V- Chemical compositions (inwt%) ofalloys CN3MN and CK3MCuN 47
Table VI -ASTMEl169ruggednesstesting matrixused to determinethe effectof
corrosiontestvariables inASTMG48E 47
Table VII -ASTM El169testing matrix showing the results ofASTMG48Etesting
ofwrought2205 duplex stainless steel.. 48
Table vm-ASTM El169testing matrix showingthe results ofASTM Ci,48 Etesting
I
ofcast2205 duplex stainless steel. 49
TableIX -Results ofASTMEl169 investigationinto ASTMG48Acorrosiontest
variables usingwrought AL6XN 50
TableX-List ofkvalues forFe, Cr, Ni, and Mo for CK3MCuN 51
'i
VI
\
\
List ofFigures
Figure 1-Effect ofsolutionvelocity ontimestobreakdown 52
Figure2-Compartmentalizedcell results for a316 stainless steel showingthe effect
ofcrevice solutionpH. 52
Figure 3-Effect ofchloride levelin synthetic solutions for multiple crevice assembly.
................................................................................................................................. 53
Figure4-Effectofchloridelevel in natural and dilute seawaterfor multiple crevice
assembly 54
Figure 5-Effectofoutsideto inside crevice arearatio ontimesto breakdown 55
Figure 6-Effectoftorque and effective crevice gap on critical crevicetemperature of
an austenitic stainless steel. 55
Figure 7-PlotofalphaparameterforMolybdenumversus coolingratefortypical
coolingratesusedinindustrialcastings. Thehighand lowextremes ofdiffusivity
were used. The alphaparameterinboth cases in« 1andtherefore Scheilconditions
prevail. 56
Figure 8- Soluteredistributionduring Scheil solidificationwith no solid diffusion and
complete liquid diffusion. A) onsetofsolidification; B) intermediate condition; C)
end ofsolidification; and D) characteristicphase diagram 57
Figure 9-Pseudobinary sectionofthe Fe -Ni - Cr -Mo system showing
characteristics similartothatofatypical binary eutectic diagram. Compositionsto the
left oftheeutectictriangle wouldbecome enrichedto the eutectic compositionand
formaterminal eutecticuponfinal cooling : 58
Figure 10 - SEMimageofadendritic as-welded AL6XNstructure and a
correspondingEPMAtrace showingthe segregationprofilethat commonly exist
across dendrites. The dendrite cores are depleted inMo 59
Figure 11 - Schematicrepresentationofthe concentrationprofilethat exists across
dendrite arms. There is asinusoidal variationfromthe maximumto minimum
concentrationwhichdecreases tothenominal composition as homogenizationtime is
increased 60
Figure 12 - CK3MCuNPseudo-binaryphase diagram showingthe heat treatment
temperature rangethatwas selected forthese alloys. The singlephaseregionwas
selectedto provide increased diffusionto aid homogenizationand providethe
potentialto dissolveany second phasepresent.. 61
Figure 13 -Plot ofindex ofresidual segregationversus time showingthatthe amount
oftimeto fully homogenizethe structuredecreases as the homogenizationtemperature
increases. Full homogenization at 1150°C requires 4hourswhile homogenizationat
1315 °C requires only 1hour.. ,~ 62
Figure 14 - Schematicrepresentation'ofinitial compositionprofile'Used tn dissolution
model. 63
Figure 15 -Plot ofrelativefraction 2nd phase remainingversus dissolution heat
treatmenttime. The amountofsecondphase decreases more rapidly withincreasing
temperature duetotheincreases'solute diffusivity at elevatedtemperatures 64
Vll
Figure 16-Niyama simulationfor CN3MN and CK3MCuN showingthatthe entire
casting shouldbefree ofmicroporosity 65
Figure 17 -Macrosegregation measurements performed on CK3MCuNbarwhere no
significant change inchemical composition is observed alongthe length oftheblock.
................................................................................................................................. 66
Figure 18 -(A) SEMmicrograph ofan(austenite+sigma) eutecticisland
inCK3MCuN after an 1150°C, 2hourheattreatment showingregionswhereEBSD
datawas collected. EBSD patterncollected from (B) matrixwhich is indexed as
austenite, (C) 2ndphasein eutectic island indexed as sigmaphase. (D)Primaryphase
in eutect;ic islandindexed as austenite 67
Figure 19 -(A) SEMmicrograph ofan(austenite+sigma) eutectic island
inCK3MCuN after an 1150°C, 2hourheattreatment showingregionswhere XEDS
datawas collected. XEDS datacollectedfrom (B)the austeniticmatrix, (C) sigma
phaseineutecticisland, and (D) eutectic austenite 68
Figure20 -LOMmicrographs ofas-cast and as-welded CN3MN and CK3MCuN
showingthe starting microstructureofaustenitewithinterdendritic(austenite+sigma)
eutectic islands 69
Figure21 - A)EPMAtrace across several dendrites in as-cast CK3MCuN showing
significantmicrosegregation fromthe dendrite coresto interdendriticregions. B)
Enlargedview ofthe0-10 wt% region showingthevariationofMo as afunction of
distance ; : 70
Figure22 -LOMmicrographs on CN3:t\.1Nheattreated at 1150°Cfor 1, 2, and 4
hours. Only small amounts ofdissolution are achieved inthe cast material after4
hourswhile nearcomplete dissolution ofthe sigmaphase occurs afteronly 1hourin
theweld duetothe decreases dendrite arm spacing 71
Figure23 -LOMmicrographs onCK3MCuNheattreated at 1150°Cfor 1, 2, and 4
hours.. Only small amounts ofdissolution are achieved inthe castmaterial after4
hours while nearcomplete dissolutionofthe sigmaphase occurs afteronly 1hourin
theweld duetothe decreased dendrite arm spacing 72
Figure24 -LOMmicrographs ofCN3:t\.1Nheattreated at 1205°C for 1, 2, and 4hours.
Significant dissolution seemsto occurafter 4hours 73
Figure25 -LOMmicrographs ofCK3MCuN heattreated at 1205°Cfor 1, 2, and 4
hours. Significantdissolution seemsto occur after4hours 74
Figure26 -LOMmicrographs ofCN3:t\.1N and CK3MCuNheattreated at 1260°Cfor
1hour. Dissolution isnot pc..curring atthesetemperatures becausepartial melting of
theinterdendriticregions is occurring 75
Figure 27 -Measured and calculatedvolumefraction sigmaphaseinCN3MNafter
heattreatment at 1150°C and 1205°C 75
Figure 28 -Measur~ and calculatedvolume fraction sigmaphasein CK3MCuN after
heattreatment at 1150°Cand 1205°C 76
Figure29 -EPMAtrace across an austenite graininCK3MCuN after 1205°C/4hour
heattreatment showing little orno remnant microsegregationindica~ive ofnear
completehomogenization : 77
Vlll