vacancy type defects in oxide dispersion strengthened steels v. slugeň, j. veterníková, v....
TRANSCRIPT
Vacancy type defects in oxide dispersion strengthened steels
V. Slugeň, J. Veterníková, V. Sabelová, J. Degmová, R. Hinca, M. Petriska and S. Sojak
Institute of Nuclear and Physical Engineering
Faculty of Electrical Engineering and Information Technology Slovak University of Technology
Bratislava, Slovakia
Available techniques for material studies:Positron Annihilation Spectroscopy: Conventional PALS 2-det. or 3-det. Set-
ups (for irradiated materials), digital Doppler Broadening set-up, access and experiences with PLEPS measurements at FRM-II in Garching
Moessbauer spectroscopy,
Atomic force microscopy,
Alfa, beta, gamma spectroscopy including low/background chamber,
X-ray diffraction, Barkhausen Noises measurements,
TEM, SEM,
Operating cascade accelerator for simulation of radiation induced defects via ion implantation
Institute of Nuclear and Physical Engineering
Slovak University of Technology
What kind of information we can
obtain from Positron Annihilation
Spectroscopy?
Report: EUR 22468 EN
Vladimír Slugeň
JRC-Petten, 30.8.2006
Defects density
Annealing effectiveness
Precipitation
Types of defects
Near surface region study
Microstructural changes due to irradiation, ageing,
...
Neutron-irradiation– Defect production
• Self-interstitial atom (SIA) & vacancy (V) rich regions
– Matrix damage• SIA-clusters, SIA-loops• Micro voids
– Solute atom diffusion• Precipitates• Complex defect-solute
configurations• GB segregation
Irradiation-induced changes of microstructure
x
x
x
xx
x
xxx
xx
Collision events
00,00050,001
0,00150,002
0,00250,003
0,00350,004
0,00450,005
target depth [nm]
counts
Depth profile of the helium implantation, E=250keV (SRIM simulation 105 ions)
ExperimentRadiation treatment
Dose [ions/cm2](C/cm2)
6,24.1017
(0.1)1,25.1018
(0.2)1,87.1018
(0.3)2,5.1018
(0.4)3,12.1018
(0.5)
DPAPALS 0,15 0,30 0,45 0,60 0,74
DPAPLEPS 18.55 37.10 55.64 74.19 92.74
DPA (average) calculation for different level of implantation in first 100m layer (DPAPALS) and 800nm (DPAPLEPS) of studied Fe-Cr alloys
To obtain cascade collisions in the microstructure of studied materials without neutron activation, accelerated helium ions have been used
Complementary techniques results
Experiment
SEM
x
Z SEM confirms the PLEPS results of large voids in the depth >500nm which correspondent to the helium implantation profile maxima .
1m
Technical specificationTotal accelerating voltage: 0 - 1 MVRipple factor: < 1%Energy rangefor singly charged particles: 5 keV to 1 MeV Energy spread: 70 keV – 1 MeV: 2 keV
< 70 keV: < 0,1%Beam current: 1 - 100 A
Cascade accelerator, laboratory of ion beams,
Slovak University of Technology
Radiation treatment
Experiment
PALS equipment
Pulsed low energy positron system (PLEPS)
remoderated positrons
[1] P. Sperr, W. Egger, G. Kögel, G. Dollinger, Ch. Hugenschmidt, R. Repper, C. Piochacz, Applied Surface Science 255 (2008) 35–38 [2] Hugenschmidt C., Dollinger G., Egger W., Kögel G.,Löwe B., Mayer J., Pikart P., Piochacz C., Repper R., Schreckenbach K., Sperr P., Stadlbauer M., Applied Surface Science, Volume 255, Issue 1, p. 29-32
100120140160180200220240260280300320
MLT [ps]
Temperature [°C]
Energy [keV]. For Cu 18keV~457nm
SM sample
300-320
280-300
260-280
240-260
220-240
200-220
180-200
160-180
140-160
120-140
100-120
SLUGEŇ, V. et al., Nuclear Fusion 44, 2004, 93.
100
250
400
550
45
7
37
8
30
5
23
8
17
8
12
4 78 41
140
160
180
200
220
240
260
280
300
MLT [ps]
Temperature [°C]
Depth [nm]
SS non-irradiated sample
Defects depth profiling study and studies of near-surface region. PAS and TEM results are useable for microstructural evaluation of new materials
HV10
PAS
MS
110
120
130
140
150
160
13 14 15 16 17 18 19 20 21 22
Hp=T.(20+logt)10-3 (a.u.)
Lif
etim
e t
1 (p
s)15Kh2NMFA
15Kh2MFA
200
250
300
350
400
13 14 15 16 17 18 19 20 21 22Hp=T.(20+logt)10 - 3 (a.u.)
15Kh2NMFA
15Kh2MFA
40
45
50
55
60
65
70
13 14 15 16 17 18 19 20 21 22
Hp=T.(20+logt)10 - 3 (a.u.)
15Kh2MFA
15Kh2NMFA
0 20 40 60 80 100100
120
140
160
180
200
[% fracture strain]
[p
s]
[ps]
0
50
100
150
200
250
[N/m
m 2]
[N/mm2]
Stress-strain experiments on Fe Distinct positron trapping after 80%
Hooks range (fully elastic region) Early stage of fatigue
Stress-strain diagram of pure Fe
Average positron LT in Fe after tensile strain
PAS parameters in comparison to results from
other techniques (TEM, SEM, HV10, MS, XRD).
SLUGEŇ, V., MAGULA, V.: Nuclear engineering and design 186/3, 1998
Lattice parameter vs. positron lifetime in defects in helium implanted Fe-Cr alloys. a.) Fe2.56%Cr; b.) Fe11.62%Cr
a.)
b.)
KRSJAK, V.: PhD Thesis, STU Bratislava, 2008
PAS Results - Annealing temperature for WWER-steels at 475 °C is acceptable, but PAS gives more information.
100
200
300
400
500
400425450475500525550
160
165
170
175
180
156.0
159.0
162.0
165.0
168.0
171.0
174.0
177.0
180.0
400 425 450 475 500 525 550
100
200
300
400
500
t (°C)
Dep
th (n
m)
158.2 168.1 178.1 188.0 197.9 207.8 217.8 227.7 237.6
The 3D presentation of PLEPS results (Tau1) of irradiated (1.25x10E24m-2) and annealed Sv-10KhMFT steel (WWER-440 weld).
The effectiveness of the annealing process to removing of small defects (mono/di-vacancies or Frenkel pairs) can be followed via significant decrease of parameter tau1. This figure also shows rapid increase of mentioned small defects in WWER type of RPV steels after about 480 ºC.
Slugen et al: NTD&E Int. 37 (2004) 651
15
The EPR pressure vessel in Olkiluoto 3 (Finland) – 2009
VVER-440 annealing facility VVER-440 V-213
Pressure vessel
• Corrosion reistance,• Radiation resistance –
negligible radiation swelling, small ΔDBTT (RTNDT, NDTT) and upper shelf energy (USE) decrease
• Thermal resistance,• Reduced activated steel – with
eliminated content of long-term radiactive Ni, C, Cu and Co replaced by V, Mn, Cr, Ti, W.
How should the ideal WWER-reactor steel look like and why?
Optimization of all factors affected on properties
Difficulties with irradiated RPV steels and advantages for implantation
• Radioactivity ―> special rules for handling, transport, polishing, storage... (PROBLEMS),– Reducing of volume,– Reducing of number of samples,– Application of other techniques if possible.
• PAS disturbing 60Co contribution (photopiks 1.17 and 1.33 MeV)– 1. Measurement using PLEPS (very thin samples of about 20 μm are
necessary), – 2. Measurement using 3 detector set-up in coincidence mode (takes about 2
weeks),– 3. To wait ... (T1/2(Co-60)=5.27 a).
• Ion implantation – none transmutations = none 60Co, very short half-time of decay for radionuclides, only 2 detectors measurement equipment for PAS
In ODS steels – 0 Co content (theory)
Chemical composition of studied ODS steels (in % wt.).
C Mn Ni Cr Mo Ti Al Si W Y2O3
MA 956 0.07 0.12 0.07 20 0.1 0.3 3.4 0.04 - 0.5
ODM 751 0.07 0.07 0.02 16 1.74 0.7 3.8 0.06 - 0.5
ODS Eurofer 0.1 0.44 - 9 0.01 - - 0.01 1.1 0.3
• Addition of stable oxides (Al2O3, Cr2O3, Y2O3)• Better mechanical properties – strength, toughness• Better corrosion resistance and resistance to thermal loading• Candidate materials for fuel cladding in new reactors (fast reactors)
Oxide Dispersion Strengthening might improve the swelling resistance of F/M steels
19
ODS 14%Cr ferritic steels: MA957ODS 14%Cr ferritic steels: MA957Less hardening than conventional and low activation F/M SteelsLess hardening than conventional and low activation F/M Steels
J. L. Boutard, J. L. Boutard, IAEA Technical Meeting, Vienna, 27-29 June 2011
0
100
200
300
400
500
600
700
800
0 10 20 30 40 50
9Cr1Mo
9Cr1MoVNb
F82H
JLF-1
EUROFER
9Cr2WTaV
ODS-MA957
Incr
ea
se o
f Yie
ld S
tre
ss (
MP
a)
Displacement damage (dpa)
9Cr1MoVNb
9Cr1Mo
RAFM-steels
ODS-MA957
Ttest
= Tirrad
= 300-325°C
Experimental techniques
• Positron annihilation lifetime spectroscopy (PALS)− Slovak University of Technology, Slovakia
• Doppler Broadening Spectroscopy (DBS) − Aalto University, Finland
• Magnetic Barkhausen Noise (MBN) − JRC, Petten, Netherland
PALS meaurement – MLT
Results of Positron Annihilation Lifetime
Spectroscopy: Lifetimes (a); Intensities (b).
ODM 751 had visible higher values – 250 ps. This signifies that MA 956 and ODS Eurofer contain defects probably with the similar size of di-vacancies, although the lifetime of MA 956 has much higher deviation. According to ΔLT2, MA 956 can also contains three-vacancies. ODM 751 has three- and four-vacancy clusters. The intensities (percentages) of positron annihilation in the defects (I2) differ significantly for investigated steels, i.e. for MA 956 ~ 60%, ODM 751 - 51% and ODS Eurofer – over 70%. Observed defects are categorical and they are formed during manufacture.
a) b)
DBS results
Behavior of S- W parameters.
The highest gradient ODM 751. ODM 751 is probably by the lowest defect presence.
The signal envelope of Magnetic Barkhausen noise for frequency up to
50 Hz (depth ~ 1 mm).
The highest signal amplitude – BNA: ODM751, which demonstrates the lowest concentration of all structural defects (vacancies, precipitations, grain boundaries) than in ODS Eurofer and MA 957. It can also denote lower hardness or lower level of residual stress in ODM 751. The highest residual stress belongs to ODS Eurofer. The smallest grains were found in MA 956. The highest Hpeak as well as the coarsest grains were detected for ODM 751.
Conclusion
• ODM 751 – the lowest defect concentration, but the largest defects,
• ODS Eurofer – the higher defect concentration as well as hardness.
• No relation to chromium content as was assumed
HHardness (residual stress) increases with defect concentration growth, no with defect size growth (precipitation vs dislocation)
• Defect concentration, defet size (PALS)
• Defect concentration, defet size (DBS)
• Hardness = residual stress (MBN)
SSame or similar
results
• Influence of Cr + Mo + W and aslo Al on hardness (creation of precipitates
