Corrosion of metals and alloys in mixed gas environments at elevated temperatures

Giggins, C. S.; Pettit, F. S.

doi:10.1007/bf00603609

Cited by 223 publications

(103 citation statements)

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“…Cr = Cr, Ḡ Cr [10] C = C, Ḡ C [11] where underlining indicates a solute species. Thus, the equilibrium condition for carbide precipitation is written as: [12] in which the activity of carbide, a CrCv , is assumed to be unity, and G • , Ḡ Cr and Ḡ C the standard free energy changes for the formation of CrC v and the partial molar free energies of dissolution of Cr and C in nickel, respectively.…”

Section: Discussionmentioning

confidence: 99%

“…• C, [8][9][10][11][12][13] and the oxidation of these alloys in H 2 O-containing environments has also been reported. [14][15][16][17] In air and oxygen environments, it has been generally accepted that binary Ni-Cr alloys with Cr contents lower than 10 wt% oxidize more rapidly than pure nickel does owing to the increased concentration of cation vacancies in the NiO scale.…”

mentioning

confidence: 83%

“…Six model alloys, 10,15,20,25 and 30 Cr (all in wt%) were prepared by arc melting pure metals Ni (99.99%) and Cr (99.995%) under a protective Ar-5%H 2 gas atmosphere, using a non-consumable electrode. Cast alloy buttons were annealed at 1100…”

Section: Methodsmentioning

confidence: 99%

“…• C. 10 Alloys containing 30 wt% or more of Cr are able to develop a protective chromia layer, and much lower oxidation rates result. 10,11 Addition of water vapor to dry oxygen-based gases hinders the formation of protective chromia scale, resulting in increased oxidation rates for Ni-10Cr and Ni-20Cr alloys.…”

mentioning

confidence: 99%

“…10,11 Addition of water vapor to dry oxygen-based gases hinders the formation of protective chromia scale, resulting in increased oxidation rates for Ni-10Cr and Ni-20Cr alloys. 14 The chromia scales on Ni-25Cr alloy after reaction in Ar-O 2 and Ar-H 2 O gas mixtures exhibited different morphologies, coarse and equi-axed grains in the former environment but fine and columnar grains in the latter.…”

mentioning

confidence: 99%

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Temperature Effect on Oxidation Behavior of Ni-Cr Alloys in CO₂Gas Atmosphere

Xie

Zhang

Young

2017

J. Electrochem. Soc.

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Model Ni-Cr alloys containing 5, 10, 15, 20, 25 and 30 wt% Cr were oxidized in Ar-20 vol% CO 2 gas mixtures at temperatures of 650, 700 and 800 • C. In general, multi-layered oxide scales were observed on the surface after reaction. With increased alloy Cr content, the oxide structure changed from external NiO, plus intermediate inner oxides and an internal oxidation zone, to forming a thin chromia band at the base of the oxide scale and, at higher Cr levels, an exclusive chromia scale. Increasing temperature accelerated the oxidation kinetics of low chromium-containing alloys, but significantly reduced the oxidation rate of high chromium alloys by promoting formation of the chromia band/scale. The critical Cr concentration required for chromia scale formation and maintenance decreased with increasing temperature, in accord with diffusion theory. Intergranular carbides were formed in high Cr content alloys, indicating elevated carbon activities beneath the oxide scales. In conventional power plants, fossil fuels are burnt in air to generate electricity. This process is of low cost, but can produce a large amount of CO 2 gas, a principal contributor to global warming. To reduce CO 2 emissions, a new technology called oxy-fuel combustion has been developed. In this process, coal is burnt in a mixture of oxygen and recirculated flue gas, so the finally released flue gas consists mainly of CO 2 and water vapor. After condensation of water vapor, sequestering CO 2 gas from the flue gas is relatively easy.Unfortunately, this technology has the potential to exacerbate the corrosion problems encountered in power plants. The CO 2 gas has been found to be very corrosive to the steels of the critical heat exchanging components in boilers, producing severe oxidation and carburization of ferritic-martensitic steels. Exposed to this atmosphere, the chromia-forming steels which are used successfully in air, undergo breakaway oxidation and carburization. [1][2][3][4] In addition, increased operating temperatures to improve boiler heat efficiency are desirable to meet continuously increasing energy demand, e.g. in advanced ultra-supercritical power generation. As a result, the ferritic/martensitic and even austenitic steels currently used in traditional coal-fired power plants will not survive when the operating temperature increases to values higher than 650• C. 5-7 Under these circumstances, nickel-based alloys are alternative candidate materials, owing to their superior creep strength and corrosion resistance at higher temperatures. However, little is known about the corrosion behavior of Ni-based alloys in CO 2 -rich gases at high temperatures.The oxidation of various model Ni-Cr alloys in air and oxygen has been well investigated at temperatures between 800 and 1200• C, [8][9][10][11][12][13] and the oxidation of these alloys in H 2 O-containing environments has also been reported. [14][15][16][17] In air and oxygen environments, it has been generally accepted that binary Ni-Cr alloys with Cr contents lower than 10 wt% oxid...

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 83%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Temperature Effect on Oxidation Behavior of Ni-Cr Alloys in CO₂Gas Atmosphere

Xie

Zhang

Young

2017

J. Electrochem. Soc.

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High‐Temperature Oxidation

Sequeira

2011

Uhlig's Corrosion Handbook

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Oxidation of Superalloys in Extreme Environments

Pint¹,

Dryepondt²,

Unocic³

2010

Superalloy 718 and Derivatives

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With the current interest in increased efficiency and reduced emissions, materials in power generation systems are increasingly exposed to more aggressive environments and higher temperatures. It is important to understand how these environments can increase corrosion rates, possibly reducing performance and likely shortening component lifetimes. Superalloys like 718 and its derivatives primarily rely on the formation of an external Cr-rich oxide layer or scale for environmental protection at typical application temperatures (≤700°C). While many laboratory oxidation and creep experiments are conducted in ambient air, the application environment for these alloys often involves combustion products, such as H 2 O and CO-CO 2 . The effect of these environments is not completely understood, especially the impact of long-term exposures, typically required of superalloy components in turbines. Air and fuel impurities, especially S and Na, can result in accelerated degradation such as the well known hot corrosion attack. While the effect of environment on crack growth has been studied, less information is available on the effect of environment on creep and fatigue properties. Initial work is being conducted to better understand the role of environment on creep properties, eventually including in-situ testing. Examples are given from steam and wet air environments and comparisons of different superalloy compositions with cast versus wrought microstructures.

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Corrosion of metals and alloys in mixed gas environments at elevated temperatures

Cited by 223 publications

References 14 publications

Temperature Effect on Oxidation Behavior of Ni-Cr Alloys in CO₂Gas Atmosphere

Temperature Effect on Oxidation Behavior of Ni-Cr Alloys in CO₂Gas Atmosphere

High‐Temperature Oxidation

Oxidation of Superalloys in Extreme Environments

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Corrosion of metals and alloys in mixed gas environments at elevated temperatures

Cited by 223 publications

References 14 publications

Temperature Effect on Oxidation Behavior of Ni-Cr Alloys in CO2Gas Atmosphere

Temperature Effect on Oxidation Behavior of Ni-Cr Alloys in CO2Gas Atmosphere

High‐Temperature Oxidation

Oxidation of Superalloys in Extreme Environments

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Product

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Temperature Effect on Oxidation Behavior of Ni-Cr Alloys in CO₂Gas Atmosphere

Temperature Effect on Oxidation Behavior of Ni-Cr Alloys in CO₂Gas Atmosphere