Subsurface characterization of an oxidation-induced phase transformation and twinning in nickel-based superalloy exposed to oxy-combustion environments

Zhu, Jing; Holcomb, Gordon R.; Jablonski, Paul D.; Wise, Adam; Li, Jia; Laughlin, David E.; Sridhar, Seetharaman

doi:10.1016/j.msea.2012.04.066

Cited by 7 publications

(8 citation statements)

References 13 publications

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“…6. The quantification results showed similar elemental partition as shown in the previous study [7] using SEM-EDS mapping,…”

Section: Analytical Microscopy Resultssupporting

confidence: 85%

“…The details of these oxidation conditions can be found in ref. [7]. The furnace heating and cooling rates were slow, on the order of 100 -200 K per hour.…”

Section: Methodsmentioning

confidence: 99%

“…In the previous study [7], it was shown that some neighboring U phase and Ni-matrix grains were configured such that the longer direction of the U phase grain was parallel to the twin boundaries of the neighboring Ni-matrix grains. Such an example is shown in In this case, we say the "U"…”

Section: The Twinning-zone Microstructure and Electron Diffraction Anmentioning

confidence: 98%

“…In an earlier work [7], the high-temperature oxidation microstructure of the Inconel 939 superalloy was examined for exposures to a series of oxy-combustion environments for a number of exposure times ranging between 250-1000 hours at temperatures between 903-1094 K. It was found that the surface and sub-surface degradation resulted from high temperature oxidation due to the service environment extended deeper into the bulk alloy beyond the presence of oxides.…”

Section: Introductionmentioning

confidence: 99%

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High-temperature-oxidation-induced ordered structure in Inconel 939 superalloy exposed to oxy-combustion environments

Zhu

Wise

Nuhfer

et al. 2013

Materials Science and Engineering: A

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In the integrated oxy-fuel combustion and turbine power generation system, turbine alloys are exposed to high temperature and an atmosphere comprised of steam, CO2 and O2. While surface and internal oxidation of the alloy takes place, the microstructure in the subsurface region also changes due to oxidation that results in the loss of the strengthening precipitates. In an earlier study of the oxidation of Inconel 939 Ni-based superalloy exposed to oxy-fuel combustion environment for up to 1000 hours, a high-temperature-oxidation-induced phase transformation in the sub-surface region was noticed and a two-phase region formed at the expense of strengthening γ' phase. While one of the two phases was identified as the Ni-matrix (γ solid solution, face-center-cubic) phase, the other product phase remained unidentified. In this study, the crystal structure of the unknown phase and its orientation relationship with the parent Ni-matrix phase was investigated through electron diffraction and high-resolution transmission electron microscopy. It was determined that the crystal structure of the unknown phase could be modeled as a ternary derivative of the ordered η-Ni3Ti phase (D024) structure with lattice parameters of a = 0.5092 nm and c = 0.8336 nm, α = 90º, β = 90º and γ = 120º. Highlights Oxidation products of the turbine material, Inconel 939 Ni-based superalloy, were studied in simulated oxy-fuel combustion conditions, focusing on the products of the decomposition the strengthening γ' precipitates.  An oxidation-induced phase transformation occurred in the subsurface region.  One of the two product phases was not included in the Ni database of ThermoCalc.  Through systematic electron microscopy investigation, this unknown phase was determined (modeled) as a ternary derivative of the ordered η-Ni 3 Ti phase (D0 24 ) in Ni-Ti-Ta system. AbstractIn the integrated oxy-fuel combustion and turbine power generation system, turbine alloys are exposed to high temperature and an atmosphere comprised of steam, CO 2 and O 2 . While surface and internal oxidation of the alloy takes place, the microstructure in the subsurface region also changes due to oxidation that results in the loss of the Manuscript Click here to view linked References 2 strengthening precipitates. In an earlier study of the oxidation of Inconel 939 Ni-based superalloy exposed to oxy-fuel combustion environment for up to 1000 hours, a hightemperature-oxidation-induced phase transformation in the sub-surface region was noticed and a two-phase region formed at the expense of strengthening γ' phase. While one of the two phases was identified as the Ni-matrix (γ solid solution, face-center-cubic) phase, the other product phase remained unidentified. In this study, the crystal structure of the unknown phase and its orientation relationship with the parent Ni-matrix phase was investigated through electron diffraction and high-resolution transmission electron microscopy. It was determined that the crystal structure of the unknown phase could be model...

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“…6. The quantification results showed similar elemental partition as shown in the previous study [7] using SEM-EDS mapping,…”

Section: Analytical Microscopy Resultssupporting

confidence: 85%

“…The details of these oxidation conditions can be found in ref. [7]. The furnace heating and cooling rates were slow, on the order of 100 -200 K per hour.…”

Section: Methodsmentioning

confidence: 99%

Section: The Twinning-zone Microstructure and Electron Diffraction Anmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

High-temperature-oxidation-induced ordered structure in Inconel 939 superalloy exposed to oxy-combustion environments

Zhu

Wise

Nuhfer

et al. 2013

Materials Science and Engineering: A

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show abstract

“…In both cases, changes in the composition at the An oxidation study on Ni-based superalloy IN-939 by Zhu [100] revealed stacking faults (twinning microstructure) in the subsurface zone due to the phase transformation driven by a composition change and also by local stresses associated with the transformation. Also, an isothermal oxidation study of nickel-base superalloy RR100 has been performed by Cruchley [101].…”

Section: Formation Of New Phasementioning

confidence: 98%