Characteristics of Oxidation and Oxygen Penetration of Alloy 690 in 600 °C Aerated Supercritical Water

Zhong, Xiangyu; Wu, Xi; Han, En‐Hou

doi:10.1016/j.jmst.2016.11.001

Cited by 30 publications

(5 citation statements)

References 39 publications

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“…6b-d and 7c, d. The intergranular oxidation was also observed on other kinds of alloys in a high-temperature water environment [31][32][33][34][35][36][37][38][39], revealing that intergranular selective oxidation of Cr is accompanied by local Cr depletion and diffusion-induced grain boundary migration, resulting in the formation of the Cr-rich oxide in the grain boundaries consisting of a porous, interconnected network of Cr 2 O 3 platelets. Katsman et al [37] assumed that the vacancies can be generated at the oxide/metal interface when consuming the Cr during the oxidation process.…”

Section: Discussionmentioning

confidence: 64%

Characterization of the Oxide Scale Formed on T12 Water Wall Tube After Long-term Service in Supercritical Power Plant

Zhong

Hamdani

et al. 2019

Oxid Met

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Oxide scale control is one of the critical maintenance issues in fossil fuel power plant. Hence, the water treatment of the feed water has been changed from all-volatile treatment (AVT) to oxygenated treatment (OT) by added some amount of oxygen in the system to form a stable oxide and minimize the scale growth rate. In this work, the oxide scales formed on T12 water wall tube after one cycle of chemical cleaning treatment under OT condition in a supercritical coal power plant were characterized by using various methods. It was found that the oxide scale formed on the inner surface of the tube had a multi-layer structure with a porous outer layer consisting of Fe 3 O 4 and Cr-rich α-Fe 2 O 3 oxides and a dense inner layer consisting of Cr-rich spinel oxide. A Cr-and Mn-enriched outermost layer was also observed. Cavities, pits, and exfoliation were observed in the oxide scales. The cavities and grain boundaries behaved as the short path of the diffusion of oxygen into the metal. Intergranular oxidation was observed between the inner layer of oxide scale and matrix. The distribution, morphology, and chemical compositional of these oxides were assessed and discussed from a point of view of the suitability of current chemical cleaning solution and procedure which has been used for AVT descaling.

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Section: Discussionmentioning

confidence: 64%

Characterization of the Oxide Scale Formed on T12 Water Wall Tube After Long-term Service in Supercritical Power Plant

Zhong

Hamdani

et al. 2019

Oxid Met

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“…However, such high mass gains were not retainable, which turned to have noticeable reductions in mass gains. The aerated water with 8 ppm oxygen at 600°C (25 MPa) resulted in noticeable mass losses [12]. The alloy 690 data under comparable pressures indicate that higher oxygen content and temperatures tended to result in greater instability to the mass changes from minor mass gains to noticeable mass losses.…”

Section: Mass Changementioning

confidence: 96%

“…Exposing alloy 690 to hydrogenated subcritical (360°C and 25 MPa) and supercritical (400°C and 25 MPa) water for up to 2,000 h did not result in a significant difference in the oxide scales, except for the observation of NiO in the outer layer, compared to that formed in the simulated primary water [10]. However, exposure of alloy 690 to aerated supercritical water (SCW) at 450-600°C with 8 part-per-million (ppm) oxygen led to more extensive oxidation with a Ni-rich outer layer including NiO, NiFe2O4 and Ni(OH)2 and a Cr-rich inner layer including Cr2O3 and NiCr2O4 [11,12]. Unlike alloy 690, reports about water or steam tests of alloy 725 at elevated temperatures are scant.…”

Section: Introductionmentioning

confidence: 96%

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Metallurgical aspects influencing the resistance to steam oxidation and fracture toughness of select advanced replacement alloys for LWR core internals

Tan

Chen

Pint

2018

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“…For the corrosion behavior of Ni–Cr alloys in SCW, it is determined that Inconel 690 produces a double-layer oxide film structure in SCW, i.e., a dense inner (barrier) layer rich in Cr and a porous, loose outer layer rich in Ni . Specifically, the inner oxide layer is composed of Cr oxides including Cr 2 O 3 and NiCr 2 O 4 spinel, while the outer oxide layer consists of Fe oxides and Ni oxides, including NiFe 2 O 4 spinel, NiO, and Ni(OH) 2 . , We should note that, since the point-defective chromia lattice contains Ni and Fe interstitials, “NiCr 2 O 4 ” may, in fact, be Cr 2 O 3 containing a high concentration of Ni 2+ interstitials.…”

Section: Corrosion Characteristics Of Ni–cr Alloysmentioning

confidence: 99%

Corrosion Characteristics of Typical Ni–Cr Alloys and Ni–Cr–Mo Alloys in Supercritical Water: A Review

Guo

et al. 2020

Ind. Eng. Chem. Res.

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The corrosion of supercritical water system materials under high-temperature and high-pressure conditions exists widely, which may result in the serious damage of the supercritical water reactor. Therefore, the improvement of the corrosion resistance of reactor material is important for ensuring the serviceability of the supercritical water reactor. This article provides a comprehensive and updated review on the corrosion characteristics of Ni−Cr and Ni−Cr−Mo corrosion-resistant alloys in supercritical water, such as the corrosion weight change, the structure, and the composition of oxide film. The influence of key parameters on the corrosion behavior of Ni-based alloys, and comparisons of corrosion resistance of typical Ni-based alloys in supercritical water, are also involved. In most cases, the corrosion weight change of different Ni−Cr−Mo alloys exposed to supercritical water (SCW) is reflected by weight gain, and first increases and then decreases with increasing exposure time over a wide range of time. The inner oxide layer is formed by the transport of anions, or conversely, of oxygen vacancies, while the outer layer is formed by the diffusion of cations but continuously dissolved. Furthermore, high temperature promotes alloy oxidation in SCW or enlarges oxide particles, thereby increasing thermal stress and eventually inducing corrosion layer exfoliation.

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Characteristics of Oxidation and Oxygen Penetration of Alloy 690 in 600 °C Aerated Supercritical Water

Cited by 30 publications

References 39 publications

Characterization of the Oxide Scale Formed on T12 Water Wall Tube After Long-term Service in Supercritical Power Plant

Characterization of the Oxide Scale Formed on T12 Water Wall Tube After Long-term Service in Supercritical Power Plant

Metallurgical aspects influencing the resistance to steam oxidation and fracture toughness of select advanced replacement alloys for LWR core internals

Corrosion Characteristics of Typical Ni–Cr Alloys and Ni–Cr–Mo Alloys in Supercritical Water: A Review

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