Studies on the hot corrosion of a nickel-base superalloy, Udimet 700

Misra, Ajay

doi:10.1007/bf00655894

Cited by 21 publications

(5 citation statements)

References 14 publications

(12 reference statements)

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“…The diffusion of S from molten salt and formation of sulfides at the corrosion front is also reported during hot corrosion in other Ni-base superalloys such as Nimonic 100, [8] B1900, [38] IN738, [39] Nimonic 105 [40] and Udimet. [41] The formation of oxides and sulfides leads to the depletion of O and S from the molten salt. It changes the basicity of the molten salt (Figure 13(c)) controlled by a Na 2 O in the melt (Eq.…”

Section: Discussionmentioning

confidence: 99%

Type-I Hot Corrosion of Ni-Base Superalloy CM247LC in Presence of Molten Na2SO4 Film

Kumawat

Parlikar

Alam

et al. 2020

Metall Mater Trans A

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Type-I hot corrosion behavior of CM247LC superalloy is evaluated in the air at 950°C against low (3 to 4), intermediate (7 to 9), and high (12 to 14 mg cm À2) Na 2 SO 4 deposits. Duration of thermal exposure is varied from a very short duration of 5 minutes to long duration of 1000 hours. The alloy shows poor corrosion resistance and undergoes complete disintegration after 500 hours of thermal exposure. Degradation of alloy increases with the increase in the duration of exposure as well as the initially deposited amount of the salt. Based on the systematic analysis of the corrosion scale, degradation mechanisms supported by the microstructural evidence are proposed. Fluxing, sulfidation-oxidation, and sulfide-undercutting are reported as the primary degradation mechanisms for CM247LC alloy in the presence of Na 2 SO 4. Self-sustaining degradation of alloy leading to complete disintegration of specimen is caused by the changeover of fluxing mechanism from basic fluxing to alloy-induced fluxing.

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Section: Discussionmentioning

confidence: 99%

Type-I Hot Corrosion of Ni-Base Superalloy CM247LC in Presence of Molten Na2SO4 Film

Kumawat

Parlikar

Alam

et al. 2020

Metall Mater Trans A

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“…For instance, in an alkali-chloride-induced corrosion situation, the presence of SO 2 can dramatically reduce the corrosion rate of some steels by transferring the corrosive chlorides to less-corrosive sulphates in a temperature between about 500 to 700 °C [19,20]; in this case, the sulphates were less corrosive than the chlorides. The researches by A. K. Mishra [17,18] showed that a higher SO 2 /SO 3 partial pressure could decrease the corrosion attack (decreasing mass gain of the samples) on the alloy U-700 rather than a lower partial pressure of SO 2 /SO 3 . Of course, the content of SO 2 should be well controlled otherwise sulfur-induced acidic corrosion would take place [19].…”

Section: Corrosion In the Ss Condition (Sulphate + So 2 + Air)mentioning

confidence: 99%

“…Mishra used the alloy U-700) by increasing the SO 2 content in the atmosphere [17,18]. Since there are very few investigations on the hot corrosion behavior of MCrAlY coatings in sulphate-plus-SO 2 environment at type-I-hot-corrosion temperatures, some hot corrosion tests were carried out in this investigation.…”

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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“…Many researches have studied the hot corrosion behavior of MCrAlY coatings in molten-sulphate environments [60][61][62][63][64][65]. The corrosion behavior of those coatings is dependent on, for example, the salt chemistry [60] and the SO 2 partial pressure [66,67]. …”

Section: Hot Corrosionmentioning

confidence: 99%

Oxidation and Corrosion of New MCrAlX Coatings : Modelling and Experiments

Yuan¹

2014

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after a high-temperature oxidation (the image height is 191 μm). Back: The profiles of alloying elements in a MCrAlY coating-superalloy system after a high-temperature oxidation (the solid curves are simulation results, and the dots are experimental ones).Printed by: LiU-Tryck, Linköping, Sweden, 2014 ISBN: 978-91-7519-247-5 ISSN 0345-7524 Distributed by: Linköping University Department of Management and Engineering SE-581 83, Linköping, Sweden © 2014 Kang YuanNo part of this publication may be reproduced or transmitted in any form without prior permission of the author.iii Abstract MCrAlY coatings ("M" for Ni and/or Co) are widely used for the protection of superalloy components operated at high temperatures such as in the hot sections of gas turbines. The exposure to high temperature can cause coating degradation due to oxidation or hot corrosion at the coating surface. Microstructures in the coating and the coating life are affected also by the diffusion of alloying elements through the coating-superalloy interface. This PhD project, by applying thermodynamic modelling and experimental tests, investigates the oxidation and hot corrosion behavior of new MCrAlX coatings, in which X, referring to minor elements, is used to highlight the functions of such elements.In order to understand and predict the coating degradation progress during thermal exposure, an oxidation-diffusion model has been established for MCrAlX coating-superalloy systems, which integrates the oxidation of aluminum at coating surface, diffusion of alloying elements, and the diffusion-blocking effect in the materials. The predicted chemical composition profile and microstructure agreed well with experimental results in a CoNiCrAlYSiTa-Inconel 792 system. The model was further applied in several coating-superalloy systems to study the influence of coating composition, superalloy composition and temperature on the evolution of microstructure in the coating and the coating life. The results have demonstrated the potential of the model in designing new durable MCrAlX coatings. In addition to the applications in coating-superalloy systems, the model was also adapted for studying the microstructural development in a superalloy in which internal oxidation and nitridation occurred in an oxidation process.The oxidation behavior of some HVOF MCrAlX coatings was studied by thermal exposure at different temperatures (900, 1000, 1100 °C). Different spinels formed above the alumina scale, depending on the oxidation temperature. The minor alloying elements, Ru and Ir, had no direct influence on the oxidation behavior but may affect the phase stability in the coating.MCrAlX coatings were also tested in 48-hour cycles at 900 °C in different hot corrosion environments containing sulphates and/or SO 2 . The results showed that the coating performance was dependent on coating quality, concentration of Al and Cr in the coating, and the hot corrosion condition. It was also found that the addition of SO 2 in the environment may not necessarily be bad for hot cor...

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Studies on the hot corrosion of a nickel-base superalloy, Udimet 700

Cited by 21 publications

References 14 publications

Type-I Hot Corrosion of Ni-Base Superalloy CM247LC in Presence of Molten Na2SO4 Film

Type-I Hot Corrosion of Ni-Base Superalloy CM247LC in Presence of Molten Na2SO4 Film

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

Oxidation and Corrosion of New MCrAlX Coatings : Modelling and Experiments

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