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Research Papers

Oxidation Performance Coating for Future Supercritical Power Plants

[+] Author and Article Information
Maria Oksa

VTT Technical Research Centre of Finland Ltd.,
Kemistintie 3, P.O. Box 1000, 02044 VTT Espoo, Finland
e-mail: Maria.Oksa@vtt.fi

Satu Tuurna

VTT Technical Research Centre of Finland Ltd.,
Sinitaival 6, 33720 Tampere, Finland
e-mail: Satu.Tuurna@vtt.fi

Jarkko Metsäjoki

VTT Technical Research Centre of Finland Ltd.,
P.O. Box 1000, 02044 VTT Espoo, Finland
e-mail: Jarkko.Metsajoki@vtt.fi

Sami Penttilä

VTT Technical Research Centre of Finland Ltd.,
P.O. Box 1000, 02044 VTT Espoo, Finland
e-mail: Sami.Penttila@vtt.fi

Manuscript received May 30, 2015; final manuscript received August 12, 2015; published online December 9, 2015. Assoc. Editor: Thomas Schulenberg.

ASME J of Nuclear Rad Sci 2(1), 011018 (Dec 09, 2015) (8 pages) Paper No: 15-1103; doi: 10.1115/1.4031379 History: Received May 30, 2015; Accepted August 12, 2015

For improved efficiency and reduced emissions, the future power plants need to operate at high temperatures and pressures, which however are limited by the durability of conventional materials such as ferritic steels. Steam oxidation of a number of coatings (Al slurries, thermal spraying, chemical vapor deposition siliconizing, and nickel plating) has demonstrated the feasibility of coatings to improve oxidation resistance. Al slurry coatings combine good high-temperature oxidation resistance through the growth of an Al2O3 layer and the possibility to apply the coating on an industrial scale at moderate cost. This work aimed to test the oxidation performance of coatings and reference alloys in ultra-supercritical (USC) water. The tested materials included Al slurry coating on ferritic 9%Cr steel and nickel-based A263 substrates, and bulk P92, MARBN, and A263 alloys as reference specimens. Oxidation resistance was tested by exposure to flowing supercritical water (SCW) with 125 ppb dissolved oxygen at 650°C (1202°F)/25MPa (3625 psi) up to 1000 hr.

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References

Figures

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Fig. 6

SEM (BSE-back scattered electron) image of Al slurry-coated T92 steel specimens after exposure: (a) 300 hr and (b) 1000 hr

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Fig. 7

Optical micrographs of P92 steel after exposure in similar conditions, 650°C (1202°F), 30 MPa (4351 psi): (a) 150 hr, (b) 450 hr, and (c) 900 hr. Evolution of oxide scale thicknesses (μm) during exposure is shown in the graph

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Fig. 8

SEM (BSE) images and EDX point analyses (wt.%) of Al slurry-coated T92 steel after 1000 hr testing: (a) cracking and (b) deep corrosion cavity into the substrate

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Fig. 5

SEM (BSE) images and EDX point analyses (wt.%) of the cross section of Al diffusion/slurry-coated T92 before steam oxidation exposure

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Fig. 4

Optical images of the cross sections of the Al diffusion-coated specimens after the 10 hr heat treatment: (a) T92 and (b) A263

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Fig. 3

Schematic diagram of the high-pressure steam oxidation facility: the supercritical autoclave and the associated water recirculation loop

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Fig. 2

Test specimens T92 and A263 (a) after applying the slurry coating and (b) after heat treatment

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Fig. 1

Schematic of typical oxide scale formation on P91 steel in the presence of water vapor at 600–700°C presenting external oxide scales and internal oxidation zone [11]

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Fig. 9

SEM (BSE) images of Al slurry-coated A263 nickel-base alloy specimens after exposure: (a) 300 hr and (b) 1000 hr

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Fig. 10

SEM (BSE) images and EDX point analyses (wt.%) of Al slurry-coated A263 nickel alloy after 1000 hr testing: (a) slurry coating, (b) coating-substrate interface, and (c) outer layer of the coating

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Fig. 11

SEM (BSE) image and EDX point analyses (wt.%) of A263 nickel-base alloy after the SCW oxidation exposure of 1000 hr

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Fig. 12

EDX mapping of MARBN steel after the SCW oxidation exposure of 1000 hr presenting distribution of (a) iron, (b) oxygen, and (c) chromium in the oxide layers and the subsurface

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Fig. 13

SEM (BSE) images and EDX point analyses (wt.%) of MARBN steel after the SCW oxidation exposure of 1000 hr

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Fig. 14

Weight change (log mg/cm2) of the coated T92_C and A263_C specimens and uncoated P92, MARBN, and A263 materials during the SCW oxidation exposure at 650°C (1202°F)/25  MPa (3625 psi) up to 1000 hr

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