Segregation of sulfur during growth of oxide scales

Grabke, H. J.; Wiemer, David F.; Viefhaus, H.

doi:10.1016/0169-4332(91)90038-l

Cited by 162 publications

(60 citation statements)

References 21 publications

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“…[1] This result suggests that Pt somehow counters the detrimental role of S. One suggested mechanism for the effect of S on scale adhesion is that it increases the growth of interfacial voids. [11,12] The addition of Pt to CVDNiAl appeared to have reduced or eliminated this type of void growth, thereby improving contact between the metal and scale. [13] The comparison of simple and Pt-modified CVD a l u m i n i d e coatings on René N5 also demonstrated that Pt did not (1) reduce the alumina scale growth rate, (2) alter the diffusion of heavy elements into the coating during deposition or oxidation, or (3) alter the coating Al content before or after oxidation.…”

Section: Resultsmentioning

confidence: 99%

Compositional Effects on Aluminide Oxidation Performance: Objectives for Improved Bond Coats

Pint¹,

Haynes²,

More³

et al. 2000

Superalloys 2000 (Ninth International Symposium)

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In order to achieve long thermal barrier coating lifetimes, underlying metallic bond coats need to form adherent, slowgrowing A l 2 O 3 layers. A set of guidelines for developing aluminide bond coat compositions is proposed in order to maximize oxidation performance, i.e. forming a slow-growing adherent alumina scale. These criteria are based on results from cast, model alloy compositions and coatings made in a laboratoryscale chemical vapor deposition facility. Aluminide coatings are thought to have more long-range potential because of their lower coefficient of thermal expansion compared to MCrAlYs. The role of Pt in improving alumina scale adhesion and countering the detrimental role of indigenous sulfur is discussed. However, the improvements associated with Pt are minimal compared to reactive element doping. One strategy which has great promise for improvement is to incorporate Hf into the coating. From an oxidation standpoint, this would preclude the need for Pt in the coating and also reduce the scale growth rate. While excellent oxidation performance was observed for cast Hf-doped NiAl, its benefits can be compromised and even eliminated by co-doping with elements such as Cr,Ti, Ta and Re. Creating a pure Hf-doped NiAl is one promising approach for improving the oxidation performance of bond coats.

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Section: Resultsmentioning

confidence: 99%

Compositional Effects on Aluminide Oxidation Performance: Objectives for Improved Bond Coats

Pint¹,

Haynes²,

More³

et al. 2000

Superalloys 2000 (Ninth International Symposium)

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“…Sulphur segregation would reduce the surface energy, adversely reducing the scale adherence. Sulphur also prefers to segregate to free surfaces, favoring the formation of voids under the oxide scale and accelerating their growth to cavities (Grabke, Wiemer, and Viefhaus 1991). The behavior of NiAI(Zr) alloys under isothermal and cyclic oxidation conditions has been sufficiently characterized that life prediction can be made with reasonable accuracy (Doychak, Smialek, and Barrett 1989;Nesbitt and Vinarcik 1991).…”

Section: Environmental Resistancementioning

confidence: 99%

The Physical and Mechanical Metallurgy of NiAl

Noebe¹,

Bowman²,

Nathal³

1996

Physical Metallurgy and Processing of Intermetallic Compounds

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“…44 A number of studies indicate that strong interfacial segregation does indeed occur. The XPS work above 39 detected strong segregation underneath the native oxide film during heating.…”

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confidence: 98%

Advances in the oxidation resistance of high‐temperature turbine materials

Smialek

2001

Surface & Interface Analysis

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This overview highlights some of the key factors in understanding the protective ability of aluminum oxide scales for current gas turbine engine alloys and coatings. Dense, phase-pure, slow-growing and adherent scales are required. In most cases, solutions have been found through educated empiricism, with more complete understanding often lagging by decades. Nevertheless, the relentless application of new techniques to answer old questions has often provided radically different viewpoints and pointed the way to new engineering developments. Equally important, this understanding prevents prior misconceptions from taking too strong a hold and maintaining a limited perspective. The microstructure, kinetics, shortcircuit diffusion, phase transformation, growth and residual stresses, interfacial segregation and adhesion provide a richness of topics for this singular and effective system. Copyright INTRODUCTIONThe successful application of many materials requires excellent high-temperature properties. For example, the thermal materials used in electric furnaces, waste incinerators, boilers, heat exchangers and heat engines all require long-term mechanical and chemical stability at high temperatures. The surface stability of the candidate material is necessary to prevent rapid material consumption at high temperatures. In general, this dictates that the exposed material is able to form a slow-growing, stable, adherent surface scale that serves to protect the underlying substrate material. The most important and effective scales are oxides; they are easily produced by reaction with the oxygen in air or in other oxygen-containing H 2 O, CO 2 or CO gaseous environments. And the most sought-after oxide scales are Al 2 O 3 , Cr 2 O 3 , and SiO 2 because of their outstanding protective qualities. Many of the high-temperature components used in aircraft and ground power gas turbines rely on these scales for protection.The purpose of the present review is to highlight some of the recent advances that have been made to high-temperature, oxidation-resistant turbine materials. It is intended to be neither comprehensive nor critical, but rather to give a general, albeit parochial, synopsis of a number of key issues seen to rise to prominence from the perspective of this author. In light of this venue, an attempt will be made to give special emphasis to advances in understanding and performance that were associated with and facilitated by various characterization and surface analysis techniques. Oxidation primerA few points regarding the basic tenents of oxidation theory relevant to all systems are worth reviewing before dealing with specific issues. (The cardinal reference text on the subject, elegantly covering all aspects in great detail, is that by Kofstad. 1 ) Very briefly, the pertinent control issues are the thermodynamics of the possible gas-solid reactions and the diffusion rates of the oxide scales in the presence of a large oxygen activity (P O 2 ) gradient. The free energy of formation of binary oxides ranges from abou...

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Segregation of sulfur during growth of oxide scales

Cited by 162 publications

References 21 publications

Compositional Effects on Aluminide Oxidation Performance: Objectives for Improved Bond Coats

Compositional Effects on Aluminide Oxidation Performance: Objectives for Improved Bond Coats

The Physical and Mechanical Metallurgy of NiAl

Advances in the oxidation resistance of high‐temperature turbine materials

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