Reactive element-sulfur interaction and oxide scale adherence

Funkenbusch, A. W.; Smeggil, J. G.; Bornstein, N. S.

doi:10.1007/bf02811687

Cited by 337 publications

(95 citation statements)

References 10 publications

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“…The casting stock was melted by Ross & Catherall in Sheffield, UK to industry-leading standards. Chemical analysis indicated less than 7.2 ppmw of sulphur in the stock, so that -since the oxidation temperatures used here are 1000ºC or lower and the tests carried out isothermally -any influence of this element on oxidation performance will be negligible [9][10][11]. Casting was carried out under the vacuum of better than 10 -4 Pa.…”

Section: Mould Preparation and Castingmentioning

confidence: 99%

A New Single Crystal Superalloy for Power Generation Applications

Reed¹,

Moverare²,

Sato³

et al. 2012

Superalloys 2012 (Twelfth International Symposium)

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The properties of a newly developed single crystal superalloyknown as STAL-15 -is described which is suitable for use in first stage blades of industrial gas turbines (IGTs). With 15 wt.% Cr and 4.55 wt.% Al, the alloy combines good corrosion and oxidation resistance with sufficient creep and fatigue performance. Traditionally, polycrystalline alloys such as IN792 and IN738LC or the single crystal alloy PWA-1483 have been used for this application; unfortunately they display only limited resistance to environmental degradation. The new alloy does not display this weakness and is therefore highly optimised for IGT applications. The new alloy is shown to be an alumina (Al2O3) former; the mechanisms behind the Al2O3-formation process are studied and the effects arising from changes in the chemical composition have been modelled. In addition, the mechanical properties in terms of creep and fatigue resistance are demonstrated together and the alloy stability evaluated during long term (up to 10,000 hours) exposure. For such applications, the new alloy is superior to existing nickel-based single crystal superalloys designed for aeroengine applications and which are optimised for very high creep resistance. The absence of Re contributes to a lower cost of alloy stock, and enhanced castability.

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Section: Mould Preparation and Castingmentioning

confidence: 99%

A New Single Crystal Superalloy for Power Generation Applications

Reed¹,

Moverare²,

Sato³

et al. 2012

Superalloys 2012 (Twelfth International Symposium)

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show abstract

“…The segregation of indigenous sulfur impurity from an alloy to the Ah03 scale/alloy interface during high temperature oxidation is often considered the major cause that weakens the interface [1][2][3][4]' Systematic studies of the chemical changes at Ah03/alloy interfaces as a function of oxidation time have in recent years been carried out for FeCrAI [5], Fe3AI and FeAI [6,7], where the alloys normally contain about 20 ppm of sulfur. Although sulfur was found to be the major segregant at these scale/alloy interfaces, the segregation behavior, in terms of rate and amount, varied significantly with different alloys and differed from surface segregation.…”

Section: Introductionmentioning

confidence: 99%

Interfacial Segregation, Pore Formation, and Scale Adhesion on NiAl Alloys

2005

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Ni-40 and 50at%AI alloys were oxidized at 1000°C for various times in oxygen. Auger electron microscopy was used to study the interface chemistry after scale spallation in ultra high vacuum. The interfacial failure stresses were determined using a tensile pull tester and related to the interface chemistry, pore area and density. Results showed that sulfur started to segregate to areas ofthe Ah03INi40AI interface where the scale was in contact with the alloy after a complete layer of a-Ah03 developed there; the concentration then gradually increased to a steady level of~2 at%. However, sulfur did not segregate to similar areas of the Ah03INi50AI interface even after extended oxidation when it was amply present on interfacial void faces. This behavior demonstrated a strong dependence of interface segregation on NiAI alloy composition. Interfacial failure stress was found to decrease with increasing sulfur content between voids and with higher interface porosity. The level of porosity was strongly related to the sulfur content in the alloy. When Ni40AI was doped with excess sulfur, the segregation behavior did not change, but the interfacial pore density increased significantly. The detrimental effect of sulfur on scale adhesion is two-fold: to weaken the interface and to enhance interfacial pore formation.

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“…(3) Dispersed Y203 also suppresses the spalling by adsorbing S at the interface between Y203 particle and matrix. (4) This S effect model can be applied to the spalling of oxide scale formed in high temperature oxidation, although sometimesperturbed. (5) The interfacial segregation of P is not detrimental to the adherence.…”

Section: Resultsmentioning

confidence: 99%