The Chemistry of Sulfidation Corrosion-Revisited

Bornstein, N. S.; Allen, W. P.

doi:10.4028/www.scientific.net/msf.251-254.127

Cited by 24 publications

(16 citation statements)

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“…In agreement with previous studies, [3][4][5][6][7][8][9][10][11] the present work showed that YSZ was susceptible to the attack of sulfate-vanadate salt. Failure of the YSZ coating was ascribed to the infiltration of molten salt into the YSZ coating along pores and cracks in the YSZ and subsequent reaction of molten salt with Y 2 O 3 , leading to the destabilization of YSZ coating (Fig.3 and Fig.4).…”

Section: Discussionsupporting

confidence: 93%

“…Failure of the YSZ coating was ascribed to the infiltration of molten salt into the YSZ coating along pores and cracks in the YSZ and subsequent reaction of molten salt with Y 2 O 3 , leading to the destabilization of YSZ coating (Fig.3 and Fig.4). The degradation mechanism of YSZ was addressed in the previous investigations [3][4][5][6][7][8][9][10][11] . Therefore, the present study would focus on the hot corrosion mechanism of the composite YSZ/Al 2 O 3 system.…”

Section: Discussionmentioning

confidence: 99%

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IMPERMEABLE THIN Al2O3 OVERLAY FOR TBC PROTECTION FROM SULFATE AND VANADATE ATTACK IN GAS TURBINES

Mao¹

2003

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In order to improve the hot corrosion resistance of yttria-stabilized zirconia (YSZ), an Al 2 O 3 overla y has been deposited on the surface of YSZ by electron-beam physical vapor deposition. Currently, hot corrosion tests were performed on the YSZ coatings with and without Al 2 O 3 overlay in molten salt mixture (Na 2 SO 4 + 0~15wt%V 2 O 5 ) at 950 o C in order to investigate the effect of amount of vanadate on the hot corrosion behaviors. The results showed that the presence of in V 2 O 5 the molten salt exacerbates the degradation of both the monolithic YSZ coating and the composite YSZ/Al 2 O 3 system. The formation of low-melting Na 2 O-V 2 O 5 -Al 2 O 3 liquid phase is responsible for degradation of the Al 2 O 3 overlay. The Al 2 O 3 overlay acts as a barrier against the infiltration of the molten salt into the YSZ coating during exposure to the molten salt mixture with <5wt% vanadate.In the next reporting period, we will use XPS and SIMS to study the interactions between alumina overlay and molten salt containing vanadate 3

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Section: Discussionsupporting

confidence: 93%

Section: Discussionmentioning

confidence: 99%

IMPERMEABLE THIN Al2O3 OVERLAY FOR TBC PROTECTION FROM SULFATE AND VANADATE ATTACK IN GAS TURBINES

Mao¹

2003

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Section: Introductionmentioning

confidence: 99%

“…In gas turbines, the formation of corrosive deposits can take place due to a direct shedding of salts from the compressor, by adding fossil fuels for combustion, or by chemical reactions between salts and gases [4,5]. The most common salt present during hot corrosion in gas turbines is sodium sulphate -Na 2 SO 4 [1,[3][4][5]. For components experiencing temperatures above 884 °C (the melting temperature of Na 2 SO 4 ), or lower temperatures if other species like K 2 SO 4 and NaCl also are present that can decrease the melting point of the salt mixture, the involvement of the molten salts can cause fluxing of the protective oxide scale, resulting in hot corrosion damage of the alloys [2,[6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Hot corrosion of MCrAlY coatings in sulphate and SO 2 environment at 900 °C: Is SO 2 necessarily bad?

Yuan

Peng

et al. 2015

Surface and Coatings Technology

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MCrAlY coatings can be corroded due to the basic fluxing (type-I hot corrosion) of the supposeto-be protective alumina scale in a molten sulphate environment. In this study, two MCrAlY coatings, coating A (10 wt.% Al, 20 wt.% Cr) and coating B (7 wt.% Al, 28 wt.% Cr), were tested in 48-hour cycles at 900 °C in a sodium-potassium sulphate environment with and without SO 2 (500 ppm). The aim was to study the effect of SO 2 at the typical type-I-hot-corrosion temperature -900 °C. The results showed that the corrosion behavior of the MCrAlY coatings depended not only on the coating composition but also on the corrosion environment. It was found that in coating A alumina scale was more resistant in the sulphate-plus-SO 2 condition than that in the sulphate-only condition. Such phenomenon indicated a beneficial effect of SO 2 . On Coating B, however, mixed oxide layers, consisting of alumina and other oxides and sulphides, formed after a certain number of cycles in the sulphate environments with or without SO 2 gas. In this coating, the addition of SO 2 in the sulphate environment promoted the formation of non-dense chromia oxides which may form from oxidation of Cr-sulfides.

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“…5 In this case, another failure mode -hot corrosion become predominant and crucial to the lifetime of TBCs. During service, molten sulfate and vanadate salt condense on the TBCs at the temperature of 600-1000 o C. 6,7 Although zirconia itself shows good resistance to the attack of the molten sulfate or vanadate compounds arising from fuel impurities, yttria is leached out of the zirconia by the reaction with V 2 O 5 or NaVO 3 to form YVO 4 , causing the structural destabilization of ZrO 2 (i.e., transformation of the zirconia from the tetragonal and/or cubic to monoclinic phase). The structural destabilization of ZrO 2 is accompanied by a large destructive volume change, leading to large stresses within the YSZ, which eventually results in the delamination and spalling of the coating.…”

Section: List Of Graphical Materialsmentioning

confidence: 99%

IMPERMEABLE THIN Al{sub 2}O{sub 3} OVERLAY FOR TBC PROTECTION FROM SULFATE AND VANADATE ATTACK IN GAS TURBINES

Mao¹

2004

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In order to further improve the hot corrosion resistance of yttria-stabilized zirconia (YSZ) the hot corrosion resistance of YSZ coating, because the tensile stresses developed in the alumina overlay in both cases due to the mismatch in thermal expansion coefficient (TEC) between alumina and zirconia resulted in cracking of Al 2 O 3 overlay. The formation of cracks increased contact area between molten salt and Al 2 O 3 overlay, and also the penetration rate of molten salt into Al 2 O 3 overlay and YSZ coating, leading a faster and greater degradation of YSZ coating upon exposure.,In the next reporting period, we will study the effect of Al 2 O 3 overlay thickness on hot corrosion and spalling of YSZ coatings.3

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The Chemistry of Sulfidation Corrosion-Revisited

Cited by 24 publications

References 0 publications

IMPERMEABLE THIN Al2O3 OVERLAY FOR TBC PROTECTION FROM SULFATE AND VANADATE ATTACK IN GAS TURBINES

IMPERMEABLE THIN Al2O3 OVERLAY FOR TBC PROTECTION FROM SULFATE AND VANADATE ATTACK IN GAS TURBINES

Hot corrosion of MCrAlY coatings in sulphate and SO 2 environment at 900 °C: Is SO 2 necessarily bad?

IMPERMEABLE THIN Al{sub 2}O{sub 3} OVERLAY FOR TBC PROTECTION FROM SULFATE AND VANADATE ATTACK IN GAS TURBINES

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