The oxidation behavior of CoCrAI systems containing active element additions

Allam, I.M.; Whittle, D. P.; Stringer, J.

doi:10.1007/bf00609974

Cited by 217 publications

(41 citation statements)

References 24 publications

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“…10(c)). The present result is quite similar to the effect of Hf-additions on the oxidation behavior of Co-11Cr-10Al alloys containing 0.05-1.5%Hf studied by Allam et al 19 The mass gain was decreased significantly by the additions of 0.05%Hf, but further additions of Hf increased the mass gain during oxidation. Since Y and Hf are both reactive elements, the same effect on oxidation resistance is expected.…”

Section: Discussionsupporting

confidence: 93%

“…The alloying addition of interest in the present study is yttrium, which is commonly a beneficial additive for the oxidation resistance in high-temperature (Ni, Co, Fe)-Cr-Al alloys, [18][19][20][21][22] in which the beneficial effect of Y on the oxidation resistance is attributed to the modification a-Al 2 O 3 growth. However, confusing and contradicting results of rare-earth elements such as Hf, Er and Y with a various amounts on mechanical properties at elevated temperature and oxidation resistance of various alloy systems have been reported.…”

Section: Introductionmentioning

confidence: 99%

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Isothermal Oxidation Behavior of Ti-50Al Alloy with Y Additions at 800 and 900°C

Umakoshi

et al. 2006

Oxid Met

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The isothermal-oxidation behavior of Al-rich TiAl alloys containing Y up to 1.0 at.% was studied in synthetic air with a flow of 200-250 mL/min at 800 and 900°C. Oxidation kinetics and scale adherence were studied in terms of the morphological features and microstructural evolution of the oxide scale. In the specimens oxidized at 800°C, all alloys containing 0.3-1.0 at.%Y showed reduced mass gain compared to the Y-free alloy, especially for the 0.3 at.%Y alloy. Under isothermal exposure at 900°C, the addition of small amounts of Y (0.1 and 0.3 at.%) was effective in enhancing the oxidation resistance. The alloys with higher Y contents (0.6 and 1.0 at.%), on the contrary, had a reverse effect on the oxidation resistance by providing rapid diffusion paths in the form of coarse Y 2 O 3 particles close to the substrate. The improvement of oxidation resistance of the alloy with Y additions was due partly to the improved adhesion of the scale and due partly to the formation of a continuous a-Al 2 O 3 layer in the outer scale. Y segregation and/or Y 2 O 3 precipitation at the oxide grain boundaries was effective in decreasing the oxidation rate and refining the oxide grains. The thinner scale was responsible for relaxing the thermal stress and, thus the cohesion between the scale and substrate was greatly improved in Y-containing alloys.

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Section: Discussionsupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Isothermal Oxidation Behavior of Ti-50Al Alloy with Y Additions at 800 and 900°C

Umakoshi

et al. 2006

Oxid Met

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“…3b). Such behavior is similar to that reported by other investigators on the oxidation of Hf-containing alloys [12,13,[28][29][30].…”

Section: Oxidation Behaviorsupporting

confidence: 89%

Sulfur Segregation at Al2O3/γ-Νi + γ′-Ni3Al Interfaces: Effects of Pt, Cr and Hf Additions

2009

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The interfacial chemistry that developed as a result Al 2 O 3 -scale growth on c-Mi ? c 0 -Ni 3 Al alloys at 1150°C was studied using scanning Auger microscopy after the oxide layer was scratched to spall under ultra-high vacuum. The extent of scale spallation was used to evaluate semi-quantitatively the interfacial strength. The alloys investigated were primarily c 0 in structure, containing 22 at.% Al plus further additions of Pt, Cr and/or Hf. In the case of the binary c ? c 0 alloy, it was found that a sub-monolayer of sulfur segregated at the alloy/scale interface. Platinum reduced and hafnium eliminated sulfur segregation, but chromium enhanced it through Cr-S cosegregation, even on Pt-and Hf-containing alloys. Platinum also segregated slightly at the alloy/scale interface. The interface strength was a strong function of the sulfur content. Beyond the effect of eliminating S segregation, Pt and Hf both showed additional beneficial effects on alumina scale adhesion.

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“…Sulphur can segregate at the alloy/oxide interface, thus weakening the adhesion of the oxide scale to the alloy [12,13]. • The formation of RE containing ''oxide pegs'' in the scale provides mechanical keying to the substrate alloy [14][15][16]. • REs may enhance interfacial chemical bonding [17][18][19][20].…”

Section: Introductionmentioning

confidence: 98%

TEM Investigation of the Microstructure of the Scale Formed on a FeCrAlRE Alloy at 900 °C: The Effect of Y-rich RE Particles

et al. 2010

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Three oxide features: the thin and smooth protective oxide, reactive element (Ti-, Zr-or Y-rich) particles, and patches of thick oxide surrounding the Y-rich reactive element particles, were observed on a commercial FeCrAlRE alloy, Kanthal AF, exposed at 900°C. The microstructural development of the patches of thick oxide was investigated on samples exposed for 24 or 168 h in either dry O 2 or O 2 ? 40% H 2 O. Analytical transmission electron microscopy in combination with site-precision TEM sample preparation by FIB/SEM was used. In all patches a thin but continuous inward growing a-Al 2 O 3 layer was formed under a thick outward growing alumina layer, which initially consisted only of c-Al 2 O 3 . In dry O 2 , transformation of c-Al 2 O 3 (in the outer layer) to a-Al 2 O 3 had started during 24 h and a considerable amount of c-Al 2 O 3 had transformed after 168 h. The transformation originated immediately above the inward growing a-Al 2 O 3 . No such transformation occurred in O 2 ? H 2 O. The possible effects of the Y-rich RE particles, as well as the effects of water vapour, on the oxidation were discussed.

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The oxidation behavior of CoCrAI systems containing active element additions

Cited by 217 publications

References 24 publications

Isothermal Oxidation Behavior of Ti-50Al Alloy with Y Additions at 800 and 900°C

Isothermal Oxidation Behavior of Ti-50Al Alloy with Y Additions at 800 and 900°C

Sulfur Segregation at Al2O3/γ-Νi + γ′-Ni3Al Interfaces: Effects of Pt, Cr and Hf Additions

TEM Investigation of the Microstructure of the Scale Formed on a FeCrAlRE Alloy at 900 °C: The Effect of Y-rich RE Particles

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