Validation of an alloy design strategy for stable Fe–Cr–Al–Nb-X ferritic alloys using electron microscopy and atom probe tomography

Kuo, Chih-Hsiang; Shassere, Benjamin; Poplawsky, Jonathan D.; Yamamoto, Yukinori; Babu, Sudarsanam Suresh

doi:10.1016/j.matchar.2019.109987

Title: Validation of an alloy design strategy for stable Fe–Cr–Al–Nb-X ferritic alloys using electron microscopy and atom probe tomography

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Abstract

The Fe–Cr–Al–Nb ferritic alloys strengthened by A₂B Laves phases, with superior oxidation and corrosion resistance, are being considered for high temperature operation within fossil-fired steam power plants to increase process efficiency and reduce CO₂ emissions. In this paper, new sets of alloys based on Fe–30Cr–3Al–1Nb (in weight percent) were designed with (i) a high microstructural stability of Laves phase precipitates in a BCC-Fe matrix and (ii) reduced precipitate free zones along the grain boundaries, targeting an operating temperature of 700 °C. Two alloys with titanium or tungsten additions were down-selected through thermodynamic calculations with a design strategy to maximize the amount of Laves phase at 700 °C and lower the BCC solvus temperature. To validate this design strategy, the candidate alloys were cast, heat treated and aged at 700 °C, and the resulting microstructure was characterized using scanning electron microscopy and atom probe tomography. The alloys with titanium addition (1 wt%) showed monotonic precipitate coarsening. On the other hand, the alloys with tungsten addition (6 wt%) showed a reduced coarsening rate of Laves phase precipitates in the matrix up to 1008 h aging, whereas an acceleration of the precipitate coarsening after that. Atom probe tomography of this alloy revealed themore »« less

Authors:

Kuo, Chih-Hsiang ^[1];

^[2];

^[2]; Babu, Sudarsanam Suresh ^[3]

Univ. of Tennessee, Knoxville, TN (United States)
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Publication Date:: Sat Nov 02 00:00:00 EDT 2019

Research Org.:: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:: USDOE Office of Fossil Energy (FE)

OSTI Identifier:: 1649595

Alternate Identifier(s):: OSTI ID: 1694015

Grant/Contract Number:: AC05-00OR22725

Resource Type:: Accepted Manuscript

Journal Name:: Materials Characterization

Additional Journal Information:: Journal Volume: 158; Journal Issue: 1; Journal ID: ISSN 1044-5803

Publisher:: Elsevier

Country of Publication:: United States

Language:: English

Subject:: 36 MATERIALS SCIENCE; Alloy design; FeCrAl; Atom probe tomography; Core-shell structure; Laves phase

Citation Formats


                    Kuo, Chih-Hsiang, Shassere, Benjamin, Poplawsky, Jonathan D., Yamamoto, Yukinori, and Babu, Sudarsanam Suresh. Validation of an alloy design strategy for stable Fe–Cr–Al–Nb-X ferritic alloys using electron microscopy and atom probe tomography.  United States: N. p., 2019. 
Web.  doi:10.1016/j.matchar.2019.109987.

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                    Kuo, Chih-Hsiang, Shassere, Benjamin, Poplawsky, Jonathan D., Yamamoto, Yukinori, & Babu, Sudarsanam Suresh. Validation of an alloy design strategy for stable Fe–Cr–Al–Nb-X ferritic alloys using electron microscopy and atom probe tomography.  United States.  https://doi.org/10.1016/j.matchar.2019.109987

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                    Kuo, Chih-Hsiang, Shassere, Benjamin, Poplawsky, Jonathan D., Yamamoto, Yukinori, and Babu, Sudarsanam Suresh. Sat .  
"Validation of an alloy design strategy for stable Fe–Cr–Al–Nb-X ferritic alloys using electron microscopy and atom probe tomography".  United States.  https://doi.org/10.1016/j.matchar.2019.109987.  https://www.osti.gov/servlets/purl/1649595.

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@article{osti_1649595,

  title        = {Validation of an alloy design strategy for stable Fe–Cr–Al–Nb-X ferritic alloys using electron microscopy and atom probe tomography},

  author       = {Kuo, Chih-Hsiang and Shassere, Benjamin and Poplawsky, Jonathan D. and Yamamoto, Yukinori and Babu, Sudarsanam Suresh},

  abstractNote = {The Fe–Cr–Al–Nb ferritic alloys strengthened by A₂B Laves phases, with superior oxidation and corrosion resistance, are being considered for high temperature operation within fossil-fired steam power plants to increase process efficiency and reduce CO₂ emissions. In this paper, new sets of alloys based on Fe–30Cr–3Al–1Nb (in weight percent) were designed with (i) a high microstructural stability of Laves phase precipitates in a BCC-Fe matrix and (ii) reduced precipitate free zones along the grain boundaries, targeting an operating temperature of 700 °C. Two alloys with titanium or tungsten additions were down-selected through thermodynamic calculations with a design strategy to maximize the amount of Laves phase at 700 °C and lower the BCC solvus temperature. To validate this design strategy, the candidate alloys were cast, heat treated and aged at 700 °C, and the resulting microstructure was characterized using scanning electron microscopy and atom probe tomography. The alloys with titanium addition (1 wt%) showed monotonic precipitate coarsening. On the other hand, the alloys with tungsten addition (6 wt%) showed a reduced coarsening rate of Laves phase precipitates in the matrix up to 1008 h aging, whereas an acceleration of the precipitate coarsening after that. Atom probe tomography of this alloy revealed the formation of a core-shell precipitate structure with a Nb/Si rich core and W-rich shell, while the alloy with Ti-addition did not show the core-shell structure. The detailed characterization results revealed that the core-shell structure was strongly correlated with the observed two-step coarsening mode in the tungsten containing alloy.},

  doi          = {10.1016/j.matchar.2019.109987},

  journal      = {Materials Characterization},

  number       = 1,

  volume       = 158,

  place        = {United States},

  year         = {Sat Nov 02 00:00:00 EDT 2019},

  month        = {Sat Nov 02 00:00:00 EDT 2019}

}

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