effects of cold spray chromium coatings on the properties of … · 2019-06-26 · –formation of...

Westinghouse Non-Proprietary Class 3 © 2019 Westinghouse Electric Company LLC. All Rights Reserved.

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J.E. Romero, J.L. Walters, A.J. Mueller, B.R. Maier, J.M. Partezana,

J.L. Lyons, W.A. Byers, G. Wang, A. Parsi, R.S. Stiteler, M. Limbäck

19th International Symposium on Zirconium in the Nuclear Industry

May 20th , 2019

Effects of Cold Spray Chromium Coatings on the

Properties of Zirconium Alloys

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Outline

• Cold spray chromium coating– Development

– Manufacturing scale-up

• Corrosion performance

– Normal operating conditions

– Steam at high temperature

– Interdiffusion and eutectics

• Thermo-mechanical performance

– Tensile tests

– Burst Tests

• Summary

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Cold Spray

• Deposition of chromium in solid state– Powder particles propelled at supersonic velocity

• No significant preparation of substrate or vacuum required

King et al. (2009)Assadi et al. (2016)

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Chromium-coated Cladding

• Thin adherent and dense chromium layer

• Cold spray as deposition technology

• Polishing process applied for finishing

• Substrate cladding unchanged

Chromium Coating

Optimized ZIRLO™ Cladding

20 µm

As-fabricated Chromium-coated Zirconium Cladding

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Manufacturing Scale-up

Coating and polishing of full length tubes qualified

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Corrosion - Normal Operation

Corrosion of coated areas near zero

Uniform CorrosionAutoclave

PWR Water

360°C

Open Samples

Weight gain of coated samples

primarily from uncoated inner

diameter

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Corrosion - High Temperature Steam

200 µm

Non-Coated Coated

200 µm

Minimal oxidation and retained ductility with coatings

during severe accident conditions

1200°C for one hour 1200°C for one hour

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Corrosion – High Temperature Steam

Uncoated 10 mm 10 mmCoated

200 µm200 µm

Protection of coating prevents oxygen strengthening

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Interdiffusion

Oxygen Chromium Zirconium

Cr

Cr-Zr

Zr

Cr2O3

50 µm

1300°C for 5 minutes

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Interdiffusion and Eutectic Formation

1300°C for 20 minutes

Prior -Zr

ZrO2

(O)-Zr and Cr-Zr

200 µm 200 µm

Cr2O3 and Cr

Prior -Zr

Cr-Zr

Eutectic

Cr2O3

Cavity

Deep diffusion of chromium leads to

eutectics, melting and cavitation

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Thermo-mechanical – Tensile Tests

• No significant effect on mechanical properties of substrate

• Coating remains adherent even at high strain

Type Sample Yield Stress Ultimate Strength Elongation

Coated A 1.16 1.19 1.46

Coated B 1.18 1.21 1.33

Coated C 1.17 1.20 1.46

Opt. ZIRLO Reference A 1.11 1.15 1.92

Opt. ZIRLO Reference B 1.11 1.15 1.92

Opt. ZIRLO Specification NA 1.00 1.00 1.00

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Thermo-mechanical – Thermal Creep

• Creep strain decreases with increased coating thickness

• General strengthening effect of chromium– Stronger material surrounding standard cladding

Material Sample Coating

Thickness (µm)

OD Strain

Ratio

Midwall Strain

Ratio

Chromium Coated

Cladding

A-1 18 0.76 0.76

A-2 18 0.69 0.69

B-1 42 0.59 0.59

B-2 42 0.57 0.57

ZIRLO® Reference NA 0 1.00 1.00

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Thermo-mechanical - Burst

1.4 MPa

Coated

Non-Coated

5.5 MPa 12.4 MPa

1 mm

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Performance Under Irradiation

No observable degradation during irradiation

50 µm

As-fabricated Irradiated Irradiated to 0.8 dpa

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Summary

• Cold spray chromium coatings developed for fuel cladding

• Significant benefits on corrosion resistance– Normal operation and high temperature

– Suppression of oxygen diffusion inhibits strengthening

• Positive effects on mechanical performance– Basic mechanical properties unaffected

– Improved burst and thermal creep behavior

• Inter-diffusion leads to metallurgical phenomena– Formation of intermetallics

– Deep diffusion in the presence of oxygen

– Formation of eutectics, melting and cavitation

effects of cold spray chromium coatings on the properties of … · 2019-06-26 · –formation of...

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