Sulfur segregation during the high-temperature oxidation of chromium

Fox, Peter; Lees, D. G.; Lorimer, G. W.

doi:10.1007/bf01151594

Cited by 68 publications

(17 citation statements)

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“…It has been suggested that sulfur influences scale growth, both for alumina 74 and chromia 75 . Using scanning transmission electron microscopy, Fox el al 75 have found sulfur at Cr 2 O 3 scale grain boundaries, and Lees 76 proposed that the presence of sulfur there promotes cation transport at oxide grain boundaries. Whether this is true needs to be confirmed by more studies.…”

Section: Sulfurmentioning

confidence: 99%

Impurity Effects on Alumina Scale Growth

Hou¹

2003

Journal of the American Ceramic Society

141

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Most high temperature resistant alloys oxidize to form an external alumina layer, or scale, whose slow growth protects the underlying alloy from continued aggressive oxidation. The growth of the Al 2 O 3 scale is controlled by the transport of oxygen inward and aluminum outward through it, with the rate dominated by the fastest diffusing specie down the fastest path. Components in the alloy can be incorporated into the growing Al 2 O 3 layer, hence affect the transport rates of oxygen and/or aluminum. This paper summarizes existing experimental data to assess the possible effect of these incorporated impurities on the growth rate and transport properties of Al 2 O 3 scales formed on Fe, Ni and Pt based alloys. The amount and distribution of the alloy base metal, sulfur impurity and reactive elements, such as Hf, Y, Zr and Ce, in the alumina scale are evaluated. Their effect on the oxidation and transport rates through the scale are discussed and compared with Al and O diffusion rates deduced from creep studies.

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Section: Sulfurmentioning

confidence: 99%

Impurity Effects on Alumina Scale Growth

Hou¹

2003

Journal of the American Ceramic Society

141

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“…14,11 The localization of sulfur segregation at a microscopic scale, therefore, is of great importance. TEM analyses have demonstrated the presence of S at an intact Cr 2 O 3 /Cr interface 15 and an adherent Al 2 O 3 /alloy interface, where the alumina was plasma deposited, 16 but more studies of this kind are needed.…”

Section: Introductionmentioning

confidence: 98%

Chemical and Morphological Evolution of a (NiPt)Al Bondcoat

2006

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Experimental results are reported on the chemical and microstructural evolutions of a (NiPt)Al coating, deposited on a single-crystal, nickel-base superalloy, during isothermal-oxidation tests at 1100°C, up to 50 hr. Analytical STEM studies were carried out, in conjunction with Auger experiments, in order to follow the various changes that occur in the bondcoat (b into c¢ phase transformation, TCP and a-Cr precipitation, S-diffusion pathways) and at the Al 2 O 3 /bondcoat interface. Efforts were concentrated on the effect of interfacial sulfur segregation (at both intact interfaces and void surfaces) as a function of the oxidation time and its dependence on phase transformations in the external layer of the bondcoat. An important result concerning the co-segregation of S and Cr at the alumina/ bondcoat interface was realized in this system due to Cr diffusion from the substrate into the bondcoat. This S segregation adversely affected Al 2 O 3 -bondcoat adhesion where extensive interfacial voids formed at the interface.

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“…However, Hou and Stringer 21 , Fox et a/. 22 and Hussey et a/. 23 dispute this conclusion, having all detected sulfur at intact interfaces of alumina and chromia scales on alloys.…”

Section: The Reactive Element Effect (Ree)mentioning

confidence: 82%

Interfacial scaling reactions and the reactive element effect

Pieraggi

Rapp

1994

Materials at High Temperatures

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Recent advances in the understanding of the structure and dynamics of solid/solid interfaces has led to some new answers for traditional questions about the role of the metal/scale interface in the growth of reaction product scales on pure metals. In particular, the action of interfacial dislocations in the creation and annihilation of the point defects supporting the diffusional growth of scales is of interest, as is their role as growth sites, for scales grown either by anion or cation diffusion. New knowledge about the metal/scale interface has permitted the consideration of blocking the interfacial reaction step as a means to retard the scaling kinetics and to alter the fundamental scaling mode. Such considerations seem consistent with the well-known phenomena ascribed to the reactive element effect (REE), which traditionally has been discussed for alloys forming chromia and alumina scales but has recently been extended to other metals. An insight into the REE mechanism is provided through the consideration of pinning of interfacial dislocations by the segregation of large reactive element ions, an action which poisons the usual interfacial reaction step.

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Sulfur segregation during the high-temperature oxidation of chromium

Cited by 68 publications

References 0 publications

Impurity Effects on Alumina Scale Growth

Impurity Effects on Alumina Scale Growth

Chemical and Morphological Evolution of a (NiPt)Al Bondcoat

Interfacial scaling reactions and the reactive element effect

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