Hydrogen embrittlement, revisited by in situ electrochemical nanoindentation [Elektronische Ressource] / von Afrooz Barnoush
288 Pages
English

Hydrogen embrittlement, revisited by in situ electrochemical nanoindentation [Elektronische Ressource] / von Afrooz Barnoush

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Published 01 January 2008
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Hydrogen embrittlement,
revisited by in situ electrochemical
nanoindentation
Dissertation
Zur Erlangung des Grades des
Doktors der Ingenieurwissenschaften (Dr.-Ing.)
der Naturwissenschaftlich-Technischen Fakultät III
Chemie, Pharmazie, Bio- und Werkstoffwissenschaften
der Universität des Saarlandes
Von
Dipl.-Ing. Afrooz Barnoush
Saarbrücken, 2007Eingereicht am: 16.10.2007
Tag der Kolloquiums: 14.03.2008
Dekan: Prof. Dr. Uli Müller
Vorsitzender: Prof. Dr. Hempelmann
Berichterstatter: Prof. Dr. H. Vehoff
Prof. Dr. W. Arnold
Prof. Dr. R. Johnsen
Akad. Mitarbeiter: Dr. Isabella GallinoCONTENTS
LIST OF FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi
LIST OF TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvi
ACKNOWLEDGMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii
ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xix
ZUSAMMENFASSUNG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xx
ACRONYMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxiii
SYMBOLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxv
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2. Hydrogen Embrittlement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1 Phenomenology of hydrogen embrittlement . . . . . . . . . . . . . . 5
2.2 Entry of hydrogen into metals . . . . . . . . . . . . . . . . . . . . . . 8
2.2.1 Gas phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.2.2 Liquid phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2.2.1 Mechanism of the cathodic evolution of hydrogen
from aqueous electrolytes . . . . . . . . . . . . . . . 10
2.2.2.2 Entry of electrolytic hydrogen into metals . . . . . 13
2.2.2.3 Promoter of hydrogen entry into metals . . . . . . 14
2.3 Hydrogen interaction with defects in metal . . . . . . . . . . . . . . 14
2.3.1 Point defects . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.3.2 Solutes and solute-defect complexes . . . . . . . . . . . . . . 16
2.3.3 Dislocations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.3.4 Internal boundaries . . . . . . . . . . . . . . . . . . . . . . . . 19
2.4 Experimental methodologies of HE study . . . . . . . . . . . . . . . 20
2.4.1 Conventional Methods . . . . . . . . . . . . . . . . . . . . . . 22
2.4.2 Environmental transmission electron microscopy . . . . . . 25
ii2.5 HE mechanisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
2.5.1 Hydride-induced embrittlement . . . . . . . . . . . . . . . . . 28
2.5.2 Hydrogen enhanced decohesion . . . . . . . . . . . . . . . . . 28
2.5.3 localized plasticity . . . . . . . . . . . . 31
2.6 A new approach to HE study . . . . . . . . . . . . . . . . . . . . . . . 32
3. NI-AFM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.1 Nanoindentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.2 Contact Mechanics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
3.3 Depth sensing nanoindentation . . . . . . . . . . . . . . . . . . . . . 48
3.4 Instrumentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
3.4.1 Hysitron Triboscope . . . . . . . . . . . . . . . . . . . . . . . . 55
3.4.2 Nanoindentation tips . . . . . . . . . . . . . . . . . . . . . . . 59
3.5 NI-AFM in liquid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
3.5.1 Complexities of NI in liquid . . . . . . . . . . . . . . . . . . . 64
3.5.1.1 Meniscus force . . . . . . . . . . . . . . . . . . . . . . 65
3.5.1.2 Buoyant force . . . . . . . . . . . . . . . . . . . . . . 66
3.5.2 Controlling the forces acting on the tip . . . . . . . . . . . . 67
3.6 Indentation phenomena . . . . . . . . . . . . . . . . . . . . . . . . . . 68
3.6.1 Geometry-based phenomena . . . . . . . . . . . . . . . . . . . 69
3.6.1.1 Surface roughness . . . . . . . . . . . . . . . . . . . 69
3.6.1.2 Inhomogeneities . . . . . . . . . . . . . . . . . . . . . 71
3.6.1.3 The indentation size effect . . . . . . . . . . . . . . 72
3.6.2 Material-based phenomena . . . . . . . . . . . . . . . . . . . 74
3.6.2.1 Pile-up and Sink-in . . . . . . . . . . . . . . . . . . . 74
3.6.2.2 Phase transformation . . . . . . . . . . . . . . . . . 77
3.6.2.3 Pop-in . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
3.6.2.4 Creep . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
3.6.2.5 Fracture . . . . . . . . . . . . . . . . . . . . . . . . . 85
4. Experimental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
4.1 General aspects of sample preparation . . . . . . . . . . . . . . . . . 87
4.1.1 Electropolishing procedure . . . . . . . . . . . . . . . . . . . . 90
4.2 Mechanical property measurements . . . . . . . . . . . . . . . . . . 92
4.2.1 Microindentation . . . . . . . . . . . . . . . . . . . . . . . . . . 92
4.2.2 Nanoindentation . . . . . . . . . . . . . . . . . . . . . . . . . . 93
4.3 In situ electrochemical NI-AFM . . . . . . . . . . . . . . . . . . . . . 93
iii5. Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
5.1 Why not ex situ tests? . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
5.1.1 Ex situ electrochemical hydrogen charging . . . . . . . . . . 100
5.1.1.1 Nanoindentation measurements on ex situ charged
nickel . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
5.1.1.2 Microhardness on ex situ charged
nickel . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
5.1.2 Ex situ hydrogen hydrogen charging in autoclave . . . . . . 106
5.2 In situ ECNI-AFM tests on copper . . . . . . . . . . . . . . . . . . . 107
5.3 In situ tests on aluminum . . . . . . . . . . . . . . . . . 111
5.3.1 ECNI-AFM of aluminum in pH 6, sulfate solution . . . . . . 118
5.3.2 of in pH 8.9, borate buffer . . . . . . 118
5.3.3 pH effect on pop-in load in aluminum . . . . . . . . . . . . . 122
5.4 In situ ECNI-AFM tests on Fe-3wt.%Si . . . . . . . . . . . . . . . . 126
5.5 In situ tests on a FeAl intermetallic alloy . . . . . . . . 133
5.6 In situ ECNI-AFM tests on Nickel . . . . . . . . . . . . . . . . . . . 140
5.6.1 Time delay experiments . . . . . . . . . . . . . . . . . . . . . 145
5.7 In situ ECNI-AFM tests on stainless steels . . . . . . . . . . . . . . 151
5.7.1 Austenitic Stainless steel . . . . . . . . . . . . . . . . . . . . . 151
5.7.2 Super Duplex Stainless steel . . . . . . . . . . . . . . . . . . 160
5.7.3 Hydrogen effect on stainless steels . . . . . . . . . . . . . . . 173
6. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
6.1 Indentation induced homogeneous dislocation nucleation . . . . . 183
6.2 Hydrogen effect on dislocation nucleation . . . . . . . . . . . . . . . 193
6.2.1 Shear modulus . . . . . . . . . . . . . . . . . . . . . . . . . . . 204
6.2.2 Stacking fault energy . . . . . . . . . . . . . . . . . . . . . . . 206
6.2.3 Dislocation core radius . . . . . . . . . . . . . . . . . . . . . . 208
6.3 Time delay experiments . . . . . . . . . . . . . . . . . . . . . . . . . . 210
7. Conclusion and outlooks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213
7.1 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213
7.2 Outlooks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
7.2.1 Micro compression tests . . . . . . . . . . . . . . . . . . . . . 215
7.2.2 Low temperature ECNI-AFM . . . . . . . . . . . . . . . . . . 215
APPENDIX
ivA. Pop-in finder program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218
B. In situ ECNI-AFM operation . . . . . . . . . . . . . . . . . . . . . . . . . . 220
B.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220
B.2 Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221
B.2.1 Starting the software . . . . . . . . . . . . . . . . . . . . . . . 221
B.2.2 Install the sample in the electrochemical cell . . . . . . . . . 221
B.2.3 Install the electrochemical cell on the microscope stage . . 222
B.2.4 Install the nanoindentation head . . . . . . . . . . . . . . . . 223
B.2.5 Align the head on the microscope . . . . . 224
B.2.6 Put the microscope inside the chamber . . . . . . . . . . . . 225
B.2.7 Engage the tip in air . . . . . . . . . . . . . . . . . . . . . . . 225
B.2.8 the tip in electrolyte . . . . . . . . . . . . . . . . . . . 226
PUBLICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227
Peer-reviewed publications . . . . . . . . . . . . . . . . . . . . . . . . . . . 227
Conference papers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228
REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229
INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256
vLIST OF FIGURES
1.1 Global description of HE interaction aspects . . . . . . . . . . . . . . . 2
2.1 Damage parameter for different single-crystalline and polycrystalline
super-alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.2 Schematic of critical variables affecting the threshold values (K )TH
and the crack growth rate da/dt. . . . . . . . . . . . . . . . . . . . . . . 7
2.3 Schematic diagram of the metal/electrolyte interface, showing fully
and partially solvated ions. . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.4 Schematic presentation of defects in metal and accumulation of hy-
drogen atoms in the low-concentration range. . . . . . . . . . . . . . . 15
2.5 Embrittlement index from 465 tests on 34 different steel grades as
a function of yield stress. . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.6 The effect of hydrogen charging condition and temperature on¾UTS(H ydrogen)
versus¾ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23UTS(Air)
2.7 The effect of in situ hydrogen charging on the flow stress of high
purity iron at various temperatures . . . . . . . . . . . . . . . . . . . . 24
2.8 The effect of hydrogen on the mobility of dislocations infi-Ti . . . . . 26
2.9 Reduction of the separation distance between dislocations in a pileup
in 310s stainless steel due to solute hydrogen . . . . . . . . . . . . . . 27
2.10 The dependence of in situ measured crack tip opening angle, fi, on
hydrogen pressure for Fe-3wt%Si . . . . . . . . . . . . . . . . . . . . . 29
2.11 Crack tip opening angles obtained in Fe-3wt%Si single crystals after
straining. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
3.1 Schematic of the interaction between a rigid spherical indenter and
a flat surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
3.2 Graphical representation of the¾ in Huber stress tensor . . . . . . 41r
vi3.3 Graphical representation of the¾ in Huber stress tensor . . . . . . 42µ
3.4 of the¾ in Huber stress tensor . . . . . . 43z
3.5 Graphical representation of the¿ in Huber stress tensor . . . . . . 44rz
3.6 of the¾ principle stress . . . . . . . . . . . 451
3.7 Graphical representation of the¾ principle stress. . . . . . . . . . . 463
3.8 of the¿ principle shear stress . . . . . . . 4713
3.9 Loading profile and the resulted load displacement curve . . . . . . . 49
3.10 Representative load-displacement data demonstrating differences in
elasticity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
3.11 Schematic of an indenter at maximum load P with an associatedmax
total depth of h . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53max
3.12 Schematic of the NI-AFM system . . . . . . . . . . . . . . . . . . . . . 56
3.13 Schematic circuit diagram of the Hysitron TriboScope transducer
assembly. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
3.14 Schematic of a three plate capacitor force-displacement transducer
of the Hysitron Triboscope. . . . . . . . . . . . . . . . . . . . . . . . . . 57
p
3.15 Graph of 1/S versus 1/ P for a series of indents performed inmax
fused quartz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
3.16 Schematic of nanoindentation probe tips . . . . . . . . . . . . . . . . . 60
3.17 Schematics of a Berkovich indenter . . . . . . . . . . . . . . . . . . . . 61
3.18 Indentation tests on fused silica . . . . . . . . . . . . . . . . . . . . . . 62
3.19 Area function curve determined from load displacement curves given
in figure 3.18b. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
3.20 Special fluid cell tip for nanoindentation inside liquid . . . . . . . . . 65
3.21 Meniscus force acting on the nanoindenter shaft during nanoinden-
tation inside the liquid . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
3.22 Representation of wetting angle and its dependence on interfacial
energies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
3.23 Change in the meniscus force with contact angle, calculated for the
case of pure water and shaft radius of 700 μm. . . . . . . . . . . . . . 67
vii