Metal dusting of nickel‐base alloys

Grabke, H. J.; Krajak, R.; Müller‐Lorenz, E. M.; Strauß, Silke

doi:10.1002/maco.19960470904

Cited by 88 publications

(86 citation statements)

References 15 publications

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“…Thus in the competition mentioned above ± outward diffusion of Cr and oxide formation versus inward diffusion of C and metal dusting, for certain Ni-base alloys the oxide formation is strongly favoured. This explains the excellent metal dusting resistance of Alloys 602 CA and 690 which showed practically no attack in exposures up to 10 000 h [15,20] (see J. Klo Èwer et al, this issue).…”

mentioning

confidence: 91%

“…For nickel, Ni-base materials and steels with NiaFe b 2a3 another simpler reaction sequence applies, not involving the instable intermediate M 3 C [6,15,16]. After oversaturation of the metal phase, direct graphite growth into the metal phase follows, C-atoms from the supersaturated solid solution attaching to graphite basal planes [16].…”

mentioning

confidence: 98%

“…Concerning protection, similar principles as for steels apply for the chromia forming Ni-base alloys [15,20], but even higher Cr-contents than in austenites b 25 % Cr are necessary. On the other hand, the inward diffusion of C in Nibase alloys is slow, D C decreases with increasing Ni/Fe-ratio to a minimum at Ni/Fe 4/1 [21] and the diffusivity of Cr increases for high Ni-contents of the materials.…”

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confidence: 99%

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Thermodynamics, mechanisms and kinetics of metal dusting

Grabke

1998

Materials and Corrosion

207

127

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A survey is given on recent research on “metal dusting” i.e. a catastrophic carburization or rather graphitization of metals and alloys occuring in carbonaceous atmospheres at carbon activities aC>1. The thermodynamics are explained, the mechanisms for iron, low and high alloy steels, nickel and Ni‐base alloys are described and the kinetics derived for iron and low alloy steels. Protection against metal dusting is possible by the presence of sulfur in the atmosphere, since adsorbed sulfur retards carbon transfer and hems graphite nucleation. Also dense oxide layers are protective, the preconditions for the formation of Cr‐rich protectivee layers on steels and Ni‐base alloys are shortly presenteed.

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Thermodynamics, mechanisms and kinetics of metal dusting

Grabke

1998

Materials and Corrosion

207

127

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“…From the point of stability for carbides, high nickel alloys do not have any metastable carbide as an intermediate. Another mechanism 18,19) has been proposed as described below: (e) continuous carbon charging into the metal matrix comes to the supersaturation at the metal surface, resulting in the precipitation of graphite. (f) inward growth of graphite destructs the metal under transfer of metal particles into the catalyzed coke.…”

Section: Introductionmentioning

confidence: 99%

A Metallurgical Approach to Metal Dusting of Nickel-Base Alloys

Nishiyama¹,

Kudo²,

Ōtsuka³

2005

Mater. Trans.

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Preliminary laboratory corrosion tests of two conventional Ni-base alloys were conducted at 650 C for 200 h in various CO-H 2 -CO 2 -H 2 O gas mixtures. For gas mixtures of high a c and CO content, alloy 600 (75 mass %Ni-15%Cr) specimens lost its mass due to metal dusting and deposition of coke was heavy on the surface of the specimen. Meanwhile, any pit formation was not occurred on the alloy 690 (60%Ni-30%Cr) specimens. Microscopic observation indicated that for the corroded Ni-base alloy specimens, inward diffusion of carbon presumably at cracks and flaws in the oxide scale was prominent. Carbon in the diffusion zone reacted with chromium to precipitate carbides in the matrix, followed by the ''direct'' formation of graphite platelets with a lamellar structure at the revealed metal surface. This direct precipitation of graphite platelets can be considered by a eutectoid reaction, which is similar to the pearlite transformation observed in Fe-C system. In the lamellar structure, the matrix thinned with the growth of graphite plates, and small metal particles of Ni and Fe which may catalyze the coke deposition reaction were crumbled and detached from the lamella.

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“…For iron and steels, metal dusting proceeds via the formation and disintegration of a metastable carbide, cementite Fe 3 C and, at very high carbon activities, additionally Hägg carbide Fe 5 C 2 . The thermogravimetric measurements revealed a quadratic increase of deposited carbon with time which is due to the catalytic effect of the fine metal particles (some 10 nm) formed in the coke [1,2]. For nickel the disintegration proceeds by direct inward or internal growth of graphite (graphitisation), not via an instable carbide and leads to larger metal particles (some 100 nm) which are not wrapped by graphitic layers as in case of iron and steels.…”

Section: Introductionmentioning

confidence: 99%

Microprocesses of metal dusting on iron‐nickel alloys and their dependence on the alloy composition

Pippel

Woltersdorf

Grabke

2003

Materials & Corrosion

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Metal dusting of iron proceeds via the formation and disintegration of the metastable carbide Fe 3 C, and the resulting fine Fe particles in the coke further catalyse carbon deposition. By contrast, nickel disintegrates directly, and larger grains are released. As revealed by TEM and AEM techniques, in both cases the disintegration proceeds by inward growth of thin graphite filaments, the atomic basal planes of which being oriented perpendicular to the surface thus effecting a high reactivity at the growth front.Consequently, successive alloying of iron with nickel should lead to a change over from one disintegration mechanism to the other, and, in fact, we could evidence that the carbide formation takes place only up to a nickel content of about 5 wt.%. Already at a Ni concentration of 10 wt.% a direct disintegration of the metal proceeds, as it is typical for pure nickel. Furthermore, in all investigated Ni-Fe alloys a surface-near enrichment of Ni was observed which indicates a selective corrosion of Fe, decreasing with increasing Ni content of the basic alloy.

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Metal dusting of nickel‐base alloys

Cited by 88 publications

References 15 publications

Thermodynamics, mechanisms and kinetics of metal dusting

Thermodynamics, mechanisms and kinetics of metal dusting

A Metallurgical Approach to Metal Dusting of Nickel-Base Alloys

Microprocesses of metal dusting on iron‐nickel alloys and their dependence on the alloy composition

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