Diffusion of18O in massive Cr2O3 and in Cr2O3 scales at 900�C and its relation to the oxidation kinetics of chromia forming alloys

Tsai, Shirley C.; Huntz, A.M.; Dolin, C.

doi:10.1007/bf01046900

Cited by 72 publications

(73 citation statements)

References 14 publications

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“…The SIMS maps were collected for 16 O À and 18 O À isotopes. Mapping used beam currents of 100-300 pA depending on the sample analyzed; at these currents, the beam has a diameter 20-30 nm.…”

Section: Characterizationmentioning

confidence: 99%

“…1a 18 O-rich regions at the surface and within the bulk external oxide. In the region of the external scale closest to the oxide/gas interface, the oxide is composed of mostly 18 O, whereas in the region closest to the oxide-metal interface, the oxides contain a mixture of 16 O and 18 O species. This illustrates oxygen transport taking place through the external oxide to form new oxide at the alloy/ oxide interface, but at the same time new oxide forms at the gas/oxide interface, which relies on outward cation diffusion.…”

Section: Classic Oxidationmentioning

confidence: 99%

“…FIB-SIMS mapping shows the relative distributions of the 16 O and 18 O species in the oxide cross sections for the image presented in Fig. 1a 18 O-rich regions at the surface and within the bulk external oxide.…”

Section: Classic Oxidationmentioning

confidence: 99%

“…[10][11][12][13][14] Energy-dispersive x-ray analyses showed that the overall oxide morphology from the external scale to internal oxides of Cr 2 O 3 /TiO 2 in the outer scale to Al 2 O 3 internally agrees with the expected thermodynamic behavior; however, and in contrast to the thermodynamic predictions, the alloy formed an outer layer of TiO 2 , believed to be at the expense of its oxidation resistance. 14,15 Cationic diffusion is inferred from the known transport mechanisms for Cr 2 O 3 growth 16,17 and from the fact that titanium must diffuse outwards to form above the outer scale. This requires titanium diffusion through the chromia and an adequate solubility of the chromium sublattice.…”

Section: Classic Oxidationmentioning

confidence: 99%

“…This particular setup facilitated the use of the 18 O 2 isotope in two-stage isotopic exposure experiments. The samples were first exposed in research-grade oxygen (referred to as 16 O 2 ) at pO 2 = 200 mbar. The exchange furnace was reevacuated before introducing the 18 O 2 -enriched oxygen also at pO 2 = 200 mbar.…”

Section: Oxidation Experimentsmentioning

confidence: 99%

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Oxidation of a Commercial Nickel-Based Superalloy under Static Loading

Foss

Hardy

Child

et al. 2014

JOM

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The current demands of the aviation industry for increased gas-turbine efficiency necessitate higher turbine entry temperatures, requiring that alloys exhibit superior oxidation resistance. The synergistic effects of oxidation and mechanical stresses pose a complex issue. The purpose of the current research was to examine the effects of stress on the oxidation and oxygen transport in a commercial nickel-based superalloy. Fine grain RR1000 in both polished and shot-peened conditions was studied for classic (zero load) and statically loaded conditions using integrated two-stage isotopic tracing combined with focusedion-beam secondary ion mass spectrometry (FIB-SIMS). Cr 2 O 3 external oxide formed with semicontinuous TiO 2 above and below. Preferential grain boundary Al 2 O 3 internal oxide formation, c¢-dissolution, and recrystallization occurred subsurface. Oxidation mechanisms were dominated by anionic/cationic growth in the external oxide with inward oxygen transport, initially through the partially unprotective external oxide, then along internal oxide/ alloy interfaces. Loading did not influence the oxidation products formed but did bring about expedited oxidation kinetics and changes to the oxide morphology. The oxygen diffusivity D O * (910 À13 cm 2 s À1 ) ranged from 0.39 for the polished alloy to 3.7 for the shot-peened condition under compressive stress. Arguably, the most significant effects took place in the subsurface regions. Increased oxidation kinetics were attributed to the development of fast cation diffusion paths as the alloy deformed by creep.

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Section: Characterizationmentioning

confidence: 99%

Section: Classic Oxidationmentioning

confidence: 99%

Section: Classic Oxidationmentioning

confidence: 99%

Section: Classic Oxidationmentioning

confidence: 99%

Section: Oxidation Experimentsmentioning

confidence: 99%

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Oxidation of a Commercial Nickel-Based Superalloy under Static Loading

Foss

Hardy

Child

et al. 2014

JOM

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What did we learn on the reactive element effect in chromia scale since Pfeil's patent?

Chevalier

2013

Materials & Corrosion

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Materials able to form protective chromia, Cr2O3, are most of time good candidates to be used at high temperatures in oxidizing atmospheres. Minor element additions are necessary to increase their mechanical or chemical properties. Among them, the reactive elements (RE) are highly efficient to improve the high temperature oxidation behavior of alloys. Their addition in small quantity is enough to greatly decrease the oxidation rates, but above all to drastically increase the oxide scale adherence to the base materials. That was the key point of what observed Pfeil 75 years ago. Since that date, many results have been published, many theories have been proposed, and many discussions have been engaged. Until now, the reasons why RE are so efficient are not fully understood, several hypotheses have been proposed in order to explain their beneficial effect on the oxide scale formation. According to the large amounts of published papers on this topic, there is probably no single theory envisageable to explain their role, whatever their nature, the tested materials and then the native oxide scale, as well as the nature of the oxidizing atmosphere. The decrease of the oxidation rate and the improvement of the oxide layer adherence are the final results due to RE additions. Generally, RE additions favor the nucleation and the growth of scales. They decrease the oxide grain size, and consequently could change scale plasticity and creep, which can modify the growth and/or thermal stresses generated within the scale during its growth or its cooling to room temperature. They prevent the detrimental sulfur effect and suppress dislocation climb in the metal and, then, limit cation transport (poisoned interface model). 75th Pfeil's patent anniversary seems good to make a pause in order to analyze what we really understood on the reactive element effect in chromia‐forming materials.

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Grain Size Effect and Spinel Transition for Alumina Scale Thermally Grown on Rare Earth–Mg Codoped FeCrAl Alloy

Duan,

Zhang,

Liu

et al. 2024

steel research int.

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The synergistic effects of rare earth (RE) and Mg elements on the high‐temperature oxidation resistance of Fe–20Cr–6Al alloy are investigated in‐depth. The scale on RE–Mg codoped alloy mainly consists of α‐Al2O3/MgAl2O4, with many pores caused by spinel transition. Owing to the segregation of RE ion at the grain boundaries, there is a significant refinement effect of oxide grains, which improves the spallation resistance of scale and offers more grain boundary diffusion pathways for ion transport, resulting in an obvious increase of oxidation weight gain. The findings indicate that RE is beneficial for inhibiting the grow‐up of oxide grains, whereas Mg can weaken the compactness of scale.

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Diffusion of18O in massive Cr2O3 and in Cr2O3 scales at 900�C and its relation to the oxidation kinetics of chromia forming alloys

Cited by 72 publications

References 14 publications

Oxidation of a Commercial Nickel-Based Superalloy under Static Loading

Oxidation of a Commercial Nickel-Based Superalloy under Static Loading

What did we learn on the reactive element effect in chromia scale since Pfeil's patent?

Grain Size Effect and Spinel Transition for Alumina Scale Thermally Grown on Rare Earth–Mg Codoped FeCrAl Alloy

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