Influence of Hydrogen and Water Vapour on the Kinetics of Chromium Oxide Growth at High Temperature

Guillou, S.; Cabet, C.; Desgranges, Clara; Marchetti, L.; Wouters, Y.

doi:10.1007/s11085-011-9246-6

Cited by 30 publications

(12 citation statements)

References 30 publications

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“…Based on the XRD pattern and the Raman spectra, the Cr-O scale mainly composes of Cr 2 O 3 . Guillou et al [ 38 ] also found the thin external Cr-O scale is denser without any pores. Hansel et al [ 39 ] proved that local surface catalysis of H 2 O dissociation at low P O2 values causes local acceleration in the oxidation rate and the growth of protruding oxide whiskers.…”

Section: Resultsmentioning

confidence: 98%

Hydrothermal Corrosion of SiC Coupons Suppressed by Magnetron Sputtered Cr Coatings

et al. 2022

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SiC-based components are sometimes susceptible to aqueous dissolution in LWR coolant environments. To address this issue, ~10 μm thick Cr coatings was deposited on reaction-bonded silicon carbide (RBSC) plates by magnetron sputtering. Corrosion behavior of Cr-coated SiC and -uncoated SiC coupons was studied by immersing in autoclave (345°C and 16.5 MPa). The weight loss of the Cr coated SiC coupons (3.02% after the 93-days) in the autoclave tests was effectively reduced due to their Cr-coated surfaces, in contrast to the uncoated ones (20.4% after the 78-days). Moreover, microstructural and compositional evolutions were examined by using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy. It was revealed that a continuous and dense Cr2O3 layer formed on the surface after the hydrothermal corrosion, which can suppress the in-diffusion of corrosive medium.

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Section: Resultsmentioning

confidence: 98%

Hydrothermal Corrosion of SiC Coupons Suppressed by Magnetron Sputtered Cr Coatings

et al. 2022

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“…For alloy Inconel 600 and alloy Incoloy 825 with relatively lower chromium content, therefore, the breakaway corrosion was more prone to happen after a shorter time. In addition, with the same exposure temperatures and oxygen partial pressures, the defect density of oxides formed in SCW is higher than that in steam environment [54,55]. The concentrated defects of ''protective'' oxides accelerated the ingress of sulfur, further resulting in the loss of oxides' protective immune function in advance.…”

Section: Discussionmentioning

confidence: 96%

Effects of Sulfides on the Corrosion Behavior of Inconel 600 and Incoloy 825 in Supercritical Water

Wang

Tang

et al. 2015

Oxid Met

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Corrosion tests of Inconel 600 and Incoloy 825 were performed in supercritical water containing sulfides at 520°C and 25 MPa. The scales formed on Inconel 600 consisted of a thick outer layer of almost pure Ni 3 S 2 and an inner layer predominantly of Cr-rich spinels with a Ni 3 S 2 network inside. The scales of Incoloy 825 also had a multilayered structure. The outer layer primarily consisted of Ni 3 S 2 and (Ni,Fe) 3 S 4, followed by a thicker intermediate mixture layer of chromium-rich oxides, Ni 3 S 2, and (Ni,Fe) 3 S 4 , an inner layer of predominantly Cr 2 O 3 and a small amount of Ni 3 S 2 toward the substrate. Incoloy 825 showed slightly better corrosion resistance than Inconel 600 due to its higher Cr content. By means of superimposed isothermal phase diagrams and evaluation for the partial pressures of oxygen and sulfur in the designated atmosphere, the corresponding corrosion mechanisms were discussed, based on the present investigation.

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“…This was done to describe the effect of the gas composition on the chromia growth rate as well as on the electrical conductivity of chromia-based scales. 30 The apparent contradictions in results from various literature sources may partly be related to the fact that in several of the mentioned studies commercially available alloy systems were used; the results may, thus, be affected by commonly present impurities and/or minor alloying additions such as titanium and manganese. 31 A major problem in interpreting the results on the basis of point defects is that chromia growth is claimed to be dominated by grain boundary rather than lattice transport.…”

Section: Single Stage Exposuresmentioning

confidence: 98%

Effect ofin-situgas changes on thermally grown chromia scales formed on Ni–25Cr alloy at 1000°C in atmospheres with and without water vapour

Dirk

Gorr

Hänsel

et al. 2015

Materials at High Temperatures

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Regarding oxidation resistance, most high temperature alloys rely on the formation of a protective chromia surface scale during service. In the present study, the oxidation behaviour of a Ni-25%Cr model alloy was investigated during single-and two-stage oxidation in Ar-O 2 and Ar-H 2 O gas mixtures at 1000uC. In the two-stage experiments, the test gas was changed after a predefined oxidation time from dry to wet gas, and vice versa, without intermediate specimen cooling. Oxidation kinetics were measured using thermogravimetry and post exposure characterisation was accomplished using scanning and transmission electron microscopy, focused ion beam and energy dispersive X-ray spectroscopy techniques. The single stage exposure to Ar-O 2 resulted in the formation of a voided, poorly adhering chromia scale exhibiting a coarse, equi-axed morphology. In Ar-7%H 2 O a fine, columnar grained oxide scale was formed which was free of microvoidage within the scale and at the scale/metal interface and therefore exhibited excellent adherence to the metallic substrate. During two-stage exposure to Ar-O 2 and subsequently to Ar-H 2 O, a fine grained, columnar shaped oxide developed on top of the coarse oxide scale formed in the first oxidation stage. The opposite effect occurred when the exposure started in the wet environment. The mechanisms which are responsible for the observed oxidation features are discussed on the basis of classical oxidation theory in combination with previous results on oxidation of chromia forming alloys in oxygen rich gases and water vapour containing, low p(O 2 ) environments.

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Influence of Hydrogen and Water Vapour on the Kinetics of Chromium Oxide Growth at High Temperature

Cited by 30 publications

References 30 publications

Hydrothermal Corrosion of SiC Coupons Suppressed by Magnetron Sputtered Cr Coatings

Hydrothermal Corrosion of SiC Coupons Suppressed by Magnetron Sputtered Cr Coatings

Effects of Sulfides on the Corrosion Behavior of Inconel 600 and Incoloy 825 in Supercritical Water

Effect ofin-situgas changes on thermally grown chromia scales formed on Ni–25Cr alloy at 1000°C in atmospheres with and without water vapour

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