A novel method of interface exposure

Coad, J.P.; Tappin, G.; Riviére, J.C.

doi:10.1016/0039-6028(82)90544-1

Cited by 10 publications

(3 citation statements)

References 6 publications

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“…of nickel on the surface of oxidised rigid 3 mm diameter cylinders (Coad et al, 1981) were unsuccessful, which indicates the high mechanical integrity of the scale. Grain boundary directions were obtained by rotating the specimen to give an exact edge-on orientation.…”

Section: Distribution Of Directions On Nio Relative To the Ni Foil mentioning

confidence: 98%

Electron microscopy of oxide scales modified to resist high‐temperature oxidation

Chadwick

Taylor

1985

Journal of Microscopy

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The high temperature oxidation of metals and alloys is slowed to a useful extent by the presence of certain elements or their oxides in the metal or on its surface. Particles of the reactive element oxide are found in part of the oxide scale and, by an unknown mechanism, retard the diffusion of metal through oxide grain boundaries. Changes in texture are also observed, which might affect geometry of individual grain boundaries. In this study the rotational geometry of grain boundaries in nickel oxide scales has been characterized both in the presence of particles of cerium dioxide and in their absence. Proximity of the relationship of neighbouring grains to a coincidence orientation could have an important influence on diffusion rate. Ways of testing this are compared and a new method for analysing orientation data from electron diffraction is presented, which allows statistically sound conclusions to be drawn. The frequency of occurrence of coincidence orientations in the presence of CeO, is little greater than random, so one possible mechanism for the 'reactive element effect' may be rejected. I N T R O D U C T I O NThe oxidation of metals and alloys at high temperature has important economic consequences. To prolong the life of artefacts such as furnaces, jet engines and fuel elements for gascooled nuclear reactors, relatively high levels (>20%) of expensive chromium have to be used to give a protective Cr203 scale (Wallwork, 1976) and even then, loss of the scale by spalling can limit operating temperatures to well below the limits imposed by mechanical strength alone. One palliative measure is the introduction of a small proportion of certain reactive elements or their oxides into the metal by alloying or dispersion, or on its surface as a coating. This improves performance by reducing both spalling and the oxidation rate itself (Whittle 8t Stringer, 1980). The lanthanides, titanium, hafnium and thorium are all effective to varying extents. Similar results can be obtained by ion implantation. A common factor appears to be the low solubility of the reactive element in the native oxide (Caillet et al., 1983) and Ecer et al. (1982) have suggested that its segregation to grain boundaries blocks cation diffusion. There is a good deal of evidence that grain boundary transport of cations dominates oxidation processes of a variety of metals and alloys at temperature of practical importance (Stringer, 1973;Hughes et al., 1984). 0 1985 The Royal Microscopical Society 22 1

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Section: Distribution Of Directions On Nio Relative To the Ni Foil mentioning

confidence: 98%

Electron microscopy of oxide scales modified to resist high‐temperature oxidation

Chadwick

Taylor

1985

Journal of Microscopy

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“…Previous evidence (Bennett et al 1982 a) suggested th a t there could be a thin silica layer a t the base of the scale; its existence has now been clearly established and its thickness measured. By using a recently developed technique (Coad 1982), oxide scales have been stripped from the 20-25-N b stainless steel exposed in carbon dioxide for varying periods a t 825 °C. xrd exam ination of these scales has indicated th a t a continuous silica layer only developed after oxidation times between 300 and 1000 h. I t probably formed laterally beneath the Cr20 3 layer by oxidation, a t a p Qi governed by the Cr-Cr20 3 equilibrium, of sil primarily by grain-boundary diffusion from the steel.…”

Section: Discussionmentioning

confidence: 99%

Transverse microstructure of an oxide scale formed on a 20% Cr–25% Ni–niobium stabilized stainless steel

Bennett

Desport

Labun

1987

Proc. R. Soc. Lond. A

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A transverse section through a scale formed during the oxidation of 20% Cr–25% Ni–niobium stabilized stainless steel, in carbon dioxide, for 4900 h at 825 °C, has been examined by transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM). These techniques have revealed the detailed microstructure and microchemistry of the three discrete silica, rhombohedral and spinel oxide layers comprising the scale. The variation of strain, degree of oxide order and crystallinity are consistent with the growth of the rhombohedral and spinel oxide being by outward cation movement. This is controlled by diffusion through the thin, amorphous silica layer after it has grown laterally between the rhombohedral oxide layer and the steel.

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“…After oxidation the oxide scale was stripped from the alloy by the drystripping technique described in Ref. 5. Briefly, the latter technique consists of sputter-ion-coating a layer of nickel 50-100 prn thick all over a coupon at -300 "C, followed by careful removal of the nickel around three edges of the coupon, whereupon the residual mechanical stresses in the nickel film cause the oxide film to peel away from the metal along a fracture path.…”

Section: Specimens and Oxidationmentioning

confidence: 99%

Study of interfaces in oxidized Fe/Si system by XPS and XAES: Use of the Auger parameter

Riviére¹,

Crossley²

1986

Surface & Interface Analysis

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Auger Parameters for a variety of silicon compounds have been measured by a combination of XPS using both AIK, and ZrL, characteristic x-radiation, and of XAES using Bremsstrahlung radiation. The Parameters so derived have then been used to study the chemical states of silicon at and near interfaces in the oxide film formed by airand C02-oxidation of Fe/Si alloys. Supportive evidence for the interpretations is provided by the widths and shapes of the silicon ILL,,, L,, Auger peaks.

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A novel method of interface exposure

Cited by 10 publications

References 6 publications

Electron microscopy of oxide scales modified to resist high‐temperature oxidation

Electron microscopy of oxide scales modified to resist high‐temperature oxidation

Transverse microstructure of an oxide scale formed on a 20% Cr–25% Ni–niobium stabilized stainless steel

Study of interfaces in oxidized Fe/Si system by XPS and XAES: Use of the Auger parameter

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