Analysis of the Corrosion Behaviour of Vapour …...UNRESTRICTED / ILLIMITÉ -1-Analysis of the...

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Analysis of the Corrosion Behaviour of

Vapour-Deposited CrN Coated Zirconium

under Normal Operation and Accident

Scenarios

Caitlin Dever, Kevin Daub, and Heidi Nordin

May 19-23, 2019


Introduction• Zircaloy-based fuel claddings prone to excessive hydrogen

evolution during LOCA

• Use of nitride-based coatings may be used for:

• Increased hardness, protection against wear, corrosion resistance, and to reduce hydrogen ingress

• Commercially available CrN coatings were applied by PVD on Zircaloy-2 and Zr-2.5Nb substrates

• Investigations focused on corrosion resistance, accident tolerance, and the effects of irradiation

Zr(s) + 2H2O(g) → ZrO2(s) + 2H2(g)


Physical Vapour Deposition

• Vacuum deposition process using plasma sputtering bombardment

• Relatively thin films may be deposited (2-4 μm)

• Deposited coatings may be harder and more corrosion resistant than coatings deposited through cathodic arc deposition or electroplating

Ar+

Sputtering

Target

Sputtered

TargetAtom

SubstrateThin Film

Sputtering

Gas

1 µm


Experimental

• Zircaloy-2

• Uncoated

• CrN-coated

• CrN-coated and scratched• Scratches made with milling

tool, approximately 40 µm deep

• Zr-2.5Nb

• Uncoated

• CrN-coated

Coatings and materials studied

Uncoated

CrN-coated

CrN-coated and scratched


As-Prepared CrN-coated Zircaloy-2

Chromium Nitrogen Zirconium

1 μm1 μm 1 μm 1 μm


Experimental

• Solution included D2O adjusted to pHa25°C 10.5 using LiOH

• System purged with Ar for 4 hours prior to test start

• Specimens tested at 300 °C, exposed in autoclave in 30 day increments up to a total exposure of 120 days

Aqueous Corrosion Testing


CrN-coated Zircaloy-2 Aqueous Corrosion

Testing

120 days

scratched

120 days

non-scratched

AB

A

A B

B

C

C

C

2 μm 2 μm

2 μm 10 μm

A

A B

B

C

C

C

2 μm 2 μm

2 μm 10 μm

BA

A

B

A

A

B

B

C

C

D

D

Oxide

10 μm 10 μm

2 μm 10 μm

A

A

A

B

B

C

C

D

D

Oxide

10 μm 10 μm

2 μm 10 μm

B



Testing – 120 daysChromium Nitrogen OxygenZirconium

200 nm 200 nm200 nm200 nm200 nm



Testing


Experimental

• Specimens exposed in an Ar-purged quartz tube with a water flow rate of 1.5 mL/min

Steam Oxidation Testing

24 h at 400 °C

24 h at 1000 °C 24 h at 400 °C

cool

6 h at 1000 °C


CrN-coated Zircaloy-2 Steam Oxidation

Testing

200 µm

Zircaloy-2

ZrO2

2 mm

Zircaloy-2

100 µm

CrN

ZrO2

Zircaloy-2

1.4 mm

CrN

2 µm

CrN

CrN

ZrO2

200 µm

Zircaloy-4

ZrO21.8 mm

Zircaloy-4


Experimental

• Exposed in reactor to pHa25°C 10.7 adjusted using LiOD

In-reactor Testing

1.37×1013 n/cm2/s

280 °C

0n/cm2/s

280 °C

325 °C

325 °C


Zircaloy-2 Exposed In-Flux

280 °C

325 °C

Uncoated CrN-coated

2 µm

2 µm2 µm

2 µm

Zr-oxide

Zr-oxide

Cr-oxides

Cr-oxides


Zr-2.5Nb Exposed In-Flux

2 µm 2 µm

2 µm 2 µm

280 °C

325 °C

Uncoated CrN-coated

Zr-oxide

Zr-oxide

Cr-oxides

Cr-oxides


Weight Gains of CrN-coated Zircaloy-2 and

Zr-2.5Nb Tested In-reactor

0

5

10

15

20

25

30

35

40

280°C - no flux 280°C - in flux 325°C - no flux 325°C - in fluxA

ver

ag

e M

ass

Ga

in (

mg

/dm

2) Zr-2.5Nb

Zr-2.5Nb coated

-15

-10

-5

0

5

10

15

20

25

30

280°C- no flux 280°C - in flux 325°C - no flux 325°C - in flux

Av

erag

e M

ass

Ga

in (

mg

/dm

2)

Zircaloy-2

Zircaloy-2 coated

Zircaloy-2 coated+scratched


Deuterium Ingress of CrN-coated Zircaloy-2

and Zr-2.5Nb Tested In-reactor


Conclusions• PVD CrN-based coatings have been found to survive on

Zircaloy-2 under aqueous corrosion conditions and reduce overall deuterium ingress

• PVD CrN-based coatings may lower steam oxidation

• When scratched, coating adherence is not compromised and further oxidation is limited

• When exposed out-of-flux and in-flux at 280 °C and 325 °C, PVD CrN-based coatings resist severe surface oxidation


Acknowledgements• Reka Szőke (IFE-Halden) for in-reactor exposure testing

• Linruo Zhao (NRC) for coating deposition through PVD

• Connor Davis (CNL) for autoclave testing

• Sridhar Ramamur (Western University) for steam exposure testing

• Clinton Mayhew (CNL) for SEM analysis

• Brad Payne (CNL) for SIMS analysis

• Alan Britton and Ryan Macleod (CNL) for HVEMS analysis

• Travis Casagrande (McMaster University) for FIB lift-outs

• Andreas Korinek (McMaster University) for TEM/EELS analysis


Thank you. Merci.Questions?

Presenting author’s email contact:

[email protected]


Experimental

• Uniaxial tensile tests conducted at RT and 300 °C

• Specimens tested to set strains:

• 0.5%

• 1%

• 1.5%

• 2%

• Al block used to heat specimens to 300 °C

• Uniaxial Tensile Testing


Uniaxial Tensile Tests• CrN-coated Zircaloy-4 tested at 300 °C to 2% strain


Uniaxial Tensile Tests

Test Temperature (°C)

Strain (%) Presence of small cracks

25 0.5 No

25 1 No

25 1.5 No

300 1 No

300 1.5 No

300 2 Yes

300 2.5 Yes

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