3 rd leader international workshop ”design and safety analysis of alfred” pisa/bologna, sept. 4...

3rd LEADER International Workshop ”Design and safety analysis of Alfred”

Pisa/Bologna, Sept. 4th-7th, 2012

LFR material issues

Peter Szakálos, Surface and Corrosion Science, KTH email: [email protected]

P. Szakálos, 3rd LEADER International Workshop, Pisa/Bologna Sept. 4th-7th, 2012

Outline

- Fundamentals about oxidation and implications to LFR

- Developement of oxidation resistant alloys for LFR (KTH/Sandvik)

- Liquid metal embrittlement

- Creep/Irradiation

- LFR Material issues – condensed summary


High Temperature Oxidation and Corrosion

Basically very simple: For a given environment, the metal should form

either a protective oxide orno product at all.

Or in other words:Kinetics (slow) or

Thermodynamics (immunity)


Overview of protective oxides at 900C

Oxi

dat

ion

rat

e

Cr

Oxide thickness


”If cations move sufficiently to avoid development of stress and anions move in suficiently to avoid the development of cavities and porosity, a highly resistant film should develop” U.R. Evans 1963.

Then the interesting question rises how to realize the simultaneous movements in both directions?

Oxidation kinetics


P. Kofstad: OAE:Oxygen Active

(dissociative) ElementRE, REM

Y,Ce,La,Hf,Th,Zr

Most problematic!

Balanced oxide growth


Ferritic stainless and austenitic stainless 304, 316. Effect of hydrogen through 1mm interconnect at 8-900C in fuel cells.

( Z. Yang et al, publ. 2003-2007, M. Ziomek-Moroz et al, publ. 2003 and 2004)

Spallation due to hydrogen penetration: H2/airReference sample: air/air

The effect of hydrogen on oxidation


G. Hultquist, B. Tveten, E. Hörnlund Oxidation of Metals, 54(1/2), 2000, p.1-10.

Oxidation of Cr in 20 mbar O2 at 900C



G. Hultquist and P. Szakalos, KME-report 401, 2010

SIMS-profiles through the oxide layer of a commercial FeCrAlY-alloy exposed to a two step isotope labelled oxygen exposure at 900°C (20 mbar 16O2 followed by 20 mbar 18O2).

Thin surface oxide

10 wt-ppm H 30 wt-ppm H

Thick surface oxide

I.e. the optimal RE-addition in a steel depends on the exposure environment!

(Depth)(Depth)

The hydrogen effect on oxidation- unbalanced growth



-Hydrogen in the metallic substrate results in a more defective oxide (protons/water vapor)

-In particular, increased outward metal-cation transport (unbalanced growth)

Hydrogen is released when metals is oxidised by water vapour-Steam side oxidation in superheaters affects the corrosion on the combustion side


GENIUS: Corrosion tests and development

of FeCr(Ni)Al- steels


Industrial supervisor, Bo Jönsson, Sandvik Heating Technology AB (Spinodal decomposition)

Austenites and 9Cr-ferrites

Exposure in LBE 10-6 wt-% dissolved oxygen (Ar-H2O-H2) .

Cross section: 550°C, 500hr, static LBE


HAYNES 230 Ni-22Cr-14W-2Mo-0.05C

Exposed 4000h in liquid lead, 550°C. Oxygen content in the liquid lead: 10-7 wt-% O (Gas phase: Ar-H2O-H2)

Ni-base HT-alloys


Overview AluminiumOxygen

IronLead Chromium

15

550°C10-7 wt-% O2500 h

Kanthal APMT (ODS) 22Cr-5Al-3Mo-RE- superior corrosion performance!


Choise of steels for fast neutron reactors


Designing new FeCrAl-alloys and coatings

Good enough?


10Cr-8Al-RE

10Cr-6Al-RE

10Cr-4Al-RE

FeCrAl experimental alloys

10Cr-6Al

550°C10-7 wt-% O2500 h

No RE


Austenite (15-15Ti) exposed in lead and H2O/H2-gas phase

respectively

Lead

Gas phase

550°C10-7 wt-% O2500 h


LPPS-FeCrAlY coating + GESA IV

0 2 4 6 8 10 12 14 16 180

10

20

30

40

50

60

70

Ni

Y

Al

Cr

Fe

co

ncen

trati

on

[w

t%]

depth [µm]

Original FeCrAlY coating

1.4970 cladding (15-15Ti)concentration profile

(Ni, Co, Fe)CrAlYX X

High solubility in Pb High activation under irradiation

Georg Müeller, Karlsruhe Institute of Technology (KIT), ELECTRA Workshop 6-7 March Stockholm 2012


Advantages: industrial coating process homogeneous element distribution smooth surface after GESA treatment free of pores after GESA treatment perfect bonding after GESA treatment

GESA treated FeCrAlY coating

1.4970 cladding

Liquid Metal Embrittlement (LME) in 9Cr-steel (T91) exposed to LBE

-Physisorption from gaseous lead in the crack

-Reduction in surface energy and bonding

-Adsorption induced slip

Z. Hadjem-Hamouche, T. Auger, I. Guillot, Corrosion Science 51 (2009)

CCT sample in LBE. Gasphase: He-4%H2 (PLC-effect)


Data evaluated from tensile tests with constant displacement rate. Crack growt rate evaluated with a CCD-camera.

LFR requirement: 650C,100MPa,104 h

”An addition of Zr recovers creep lifetime of Al-added ODS steels by two orders of magnitude”

FeCrAl creep properties


Neutron irradiation performance of reference structural materials (XT-

ADS) J. Henry, Ph. Dubuisson CEA. Helimnet/Demetra Workshop, Berlin March 2010

T91 irradiated to 78 dpa (Ttest: 25°C)

Austenite AISI 316L:- Yield stress incresses by several hundred MPa under irradiation at ~330°C, while

the UE (uniform elongation) drops to negligible values by ~5-10 dpa. Saturation of tensile properties occur at ~10 dpa; the fracture mode is ductile even at high dose. Irradiation-induced hardening is highest in the range [300-350°C].

- Fracture toughness values remain high at 3 dpa exposure (250-300°C irr. T) but should drop with increasing dose.

9Cr-ferrite, T91: - Irradiation at ~330°C induces a huge hardening together with a complete loss of

ductility (doses>~40dpa) and a cleavage type fracture mode. Low activation steels (clean steels) exibit lower hardening and retain a ductile behaviour up to 80 dpa. At Temperatures > 400°C, there is little irradiation-induced hardening.

- As expected from the tensile behaviour, T91 impact properties are drasticly modified by irradiation at ~330°C (very large DBBT shift, catastrophic decrease of USE). Above ~400°C, 9Cr steels exibit moderate DBTT shifts. Little fracture toughness data is available in the temperature range of interest.

- 9Cr martensitic steels exibit good dimensional stability with an irradiation creep modulus (swelling) lower than that of austenitic steels.


Oxidation kinetics in air + 10% H2O

20Cr-25Ni-1.5MoNbTiN heat-resistant austenitic stainless (Nippon steel)

20Ni-14Cr-2.5Al-NbC

New ”RE”?


Steel type: Weakness:9Cr Ferrite/Martensite Oxidation, Fracture toughness in leadAustenites, type 316L Swelling, OxidationFe20CrAl Spinodal decompositionFe(12±2)CrAl Creep? Fracture toughness?FeNi(15±5)CrAl-ODS Austenite ?

LFR material issues

- condensed summary:


( Alumina former: Ti2AlC )

Rolls Royce gas turbine coatings

YSZ,Yttria

StabilizedZrO2

3 rd leader international workshop ”design and safety analysis of alfred” pisa/bologna, sept. 4...

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