Cation Diffusion in Cr[sub 2]O[sub 3]

Hagel, W. C.; Seybolt, A. U.

doi:10.1149/1.2427973

Cited by 223 publications

(79 citation statements)

References 9 publications

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“…Actually, it was reported that the cation was much more mobile in Cr 2 O 3 than was the anion. 23) The temperature dependence of k p values of chromium obtained in oxygen or in air atmosphere is shown in Fig. 9, comparing the present results with those reported by other groups.…”

Section: Discussionsupporting

confidence: 88%

Oxidation or Nitridation Behavior of Pure Chromium and Chromium Alloys Containing 10 mass%Ni or Fe in Atmospheric Heating

et al. 2006

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Section: Discussionsupporting

confidence: 88%

Oxidation or Nitridation Behavior of Pure Chromium and Chromium Alloys Containing 10 mass%Ni or Fe in Atmospheric Heating

et al. 2006

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“…The activation energies for growth were determined to be Q(OST)= 262 ± 33 kJ/mol, Q(AFD)= 218 ± 18 kJ/mol, and Q(GPD)= 285 ± 35 kJ/mol. There is good agreement for Q(OST) with the literature value for Cr 2 O 3 growth of 256 kJ/mol [14], even though TiO 2 grains have been included in the thickness determination.…”

Section: Resultssupporting

confidence: 73%

Oxidation and the Effects of High Temperature Exposures on Notched Fatigue Life of an Advanced Powder Metallurgy Disk Superalloy

Sudbrack¹,

Draper²,

Gorman³

et al. 2012

Superalloys 2012 (Twelfth International Symposium)

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Oxidation and the effects of high temperature exposures on notched fatigue life were considered for a powder metallurgy processed supersolvus heat-treated ME3 disk superalloy. The isothermal static oxidation response at 704 °C, 760 °C, and 815 °C was consistent with other chromia forming nickel-based superalloys: a TiO 2 -Cr 2 O 3 external oxide formed with a branched Al 2 O 3 internal subscale that extended into a recrystallized γ'-dissolution layer. These surface changes can potentially impact disk durability, making layer growth rates important. Growth of the external scales and γ'dissolution layers followed a cubic rate law, while Al 2 O 3 subscales followed a parabolic rate law. Cr-rich M 23 C 6 carbides at the grain boundaries dissolved to help sustain Cr 2 O 3 growth to depths about 12 times thicker than the scale.The effect of prior exposures was examined through notched low cycle fatigue tests performed to failure in air at 704 °C. Prior exposures led to pronounced debits of up to 99 % in fatigue life, where fatigue life decreased inversely with exposure time. Exposures that produced roughly equivalent 1 µm thick external scales at the various isotherms showed statistically equivalent fatigue lives, establishing that surface damage drives fatigue debit, not exposure temperature. Fractographic evaluation indicated the failure mode for the pre-exposed specimens involved surface crack initiations that shifted with exposure from predominately single intergranular initiations with transgranular propagation to multi-initiations from the cracked external oxide with intergranular propagation. Weakened grain boundaries at the surface resulting from the M 23 C 6 carbide dissolution are partially responsible for the intergranular cracking. Removing the scale and subscale while leaving a layer where M 23 C 6 carbides were dissolved did not lead to a significant fatigue life improvement, however, also removing the M 23 C 6 carbide dissolution layer led to nearly full recovery of life, with a transgranular initiation typical to that observed in unexposed specimens.

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“…Figure 5 shows a good straight line fit for the isothermal exposure data. The gradient of this line gives an activation energy of ~270 kJ/mol, which is higher than literature values (256 kJ/mol or 61.1 kcal/mol) for Cr 2 O 3 growth [6], although the tests in the current study have been carried out at much lower temperatures. Chen et al [7] reported activation energies of 250, 270 and 300 kJ/mol for nickel disc alloys Udimet 720, Astroloy and Waspaloy, which were determined from isothermal exposures and cyclic oxidation testing at 750-1000ºC.…”

Section: Characterisation Of Oxidation Kineticscontrasting

confidence: 64%

Effects of Oxidation and Hot Corrosion in a Nickel Disc Alloy

Encinas-Oropesa¹,

Drew²,

Hardy³

et al. 2008

Superalloys 2008 (Eleventh International Symposium)

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This paper describes work to study oxidation and hot corrosion damage in nickel disc alloy RR1000. Oxidation damage has been characterised via mass change data from thermogravimetric analyses at temperatures from 700 to 800 ºC and cyclic oxidation testing at 700 and 750 ºC. Thin oxide scales rich in Cr and Ti have been found to grow in a parabolic dependence with time. Oxidation rate constants have been correlated with temperature using an Arrhenius equation. Through the use of simplifying assumptions, mass change data have been converted to oxide thickness values. These values have been compared with observed values of oxide scale and the depth of near-surface damage, which have been measured using focused ion beam (FIB) microscopy.Hot corrosion of RR1000 has been studied in the laboratory by 'deposit' recoat experiments at 700ºC. In these tests, samples were coated with deposits of Na 2 SO 4 /NaCl salt in a gas stream of air-300 vpm SO 2 . Corrosion damage has been quantified by dimensional metrology of samples before and after exposure. This enabled metal losses, i.e. the depth of corrosion pits, to be determined. Distributions of metal loss data were then generated to produce median damage values and exceedance cumulative probabilities. Finally, the effect of contaminants on the hot corrosion resistance of RR1000 has also been evaluated.

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Cation Diffusion in Cr[sub 2]O[sub 3]

Cited by 223 publications

References 9 publications

Oxidation or Nitridation Behavior of Pure Chromium and Chromium Alloys Containing 10 mass%Ni or Fe in Atmospheric Heating

Oxidation or Nitridation Behavior of Pure Chromium and Chromium Alloys Containing 10 mass%Ni or Fe in Atmospheric Heating

Oxidation and the Effects of High Temperature Exposures on Notched Fatigue Life of an Advanced Powder Metallurgy Disk Superalloy

Effects of Oxidation and Hot Corrosion in a Nickel Disc Alloy

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