Microstructural evaluation of a Fe-12Cr nanostructured ferritic alloy designed for impurity sequestration

Caleb P. Massey; David T. Hoelzer; Rachel L. Seibert; Philip D. Edmondson; Anoop Kini; Baptiste Gault; Kurt A. Terrani; Steven J. Zinkle

doi:10.1016/j.jnucmat.2019.05.019

Microstructural evaluation of a Fe-12Cr nanostructured ferritic alloy designed for impurity sequestration

Caleb P. Massey, David T. Hoelzer, Rachel L. Seibert, Philip D. Edmondson, Anoop Kini, Baptiste Gault, Kurt A. Terrani, Steven J. Zinkle

Research output: Contribution to journal › Article › peer-review

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Abstract

Fast reactor fuel cladding candidate materials require proficiency in extreme environments consisting of high temperatures and irradiation doses in excess of 150 displacements per atom (dpa). Nanostructured oxide dispersion strengthened (ODS) alloys have been developed extensively for this purpose due to their notable high temperature strength, creep resistance, and irradiation resistance. However, their properties can deteriorate if interstitial impurities such as C and N are not well controlled during the fabrication process. A new Fe-12Cr nanostructured ODS alloy OFRAC (Oak Ridge Fast Reactor Advanced Fuel Cladding) with solute additions of Mo, Ti, and Nb has been developed to provide the desired properties mentioned above while simultaneously sequestering impurities within the matrix. After extrusion at 850 °C, the as-extruded microstructure consists of an average 490 nm grain size and a high number density (6.8 × 10²³ m^-3) of 2.2 nm diameter (Y,Ti,O) nanoclusters distributed homogeneously in the matrix. Atom probe tomography investigations suggest non-stochiometric compositions for the smallest nanoclusters. In addition, a second population of nanometer scale (Nb,Ti) rich carbonitrides is also present in the microstructure that captures the potentially detrimental C and N impurity atoms present in the matrix. Atom probe tomography results indicate elemental segregation of Cr, Mo, and Nb to grain boundaries in the as-extruded material, consistent with previous investigations of solid solution strengthening by solute additions. The ability of OFRAC to sequester impurities introduced from the powder metallurgical approach to nanostructured ferritic alloy development, compounded with its beneficial mechanical properties, makes this alloy a competitive candidate for fast reactor applications. This manuscript has been authored by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).

Original language	English
Pages (from-to)	111-122
Number of pages	12
Journal	Journal of Nuclear Materials
Volume	522
DOIs	https://doi.org/10.1016/j.jnucmat.2019.05.019
State	Published - Aug 15 2019

Funding

This material is based upon work supported under a Department of Energy Nuclear Energy University Program Graduate Fellowship. The work presented in this paper was supported by the Advanced Fuels Campaign of the Nuclear Technology R&D program in the Office of Nuclear Energy, U.S. Department of Energy. This manuscript has been authored by Oak Ridge National Laboratory, managed by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. A portion of this work was conducted using the FEI Talos F200X S/TEM tool provided by US DOE, Office of Nuclear Energy, Fuel Cycle R&D Program and the Nuclear Science User Facilities. The authors would like to acknowledge Tom Geer for his extensive help with metallographic sample preparation and Eric Manneschmidt for his assistance with mechanical property evaluations. This material is based upon work supported under a Department of Energy Nuclear Energy University Program Graduate Fellowship. The work presented in this paper was supported by the Advanced Fuels Campaign of the Nuclear Technology R&D program in the Office of Nuclear Energy , U.S. Department of Energy . This manuscript has been authored by Oak Ridge National Laboratory , managed by UT-Battelle , LLC , under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. A portion of this work was conducted using the FEI Talos F200X S/TEM tool provided by US DOE, Office of Nuclear Energy, Fuel Cycle R&D Program and the Nuclear Science User Facilities. The authors would like to acknowledge Tom Geer for his extensive help with metallographic sample preparation and Eric Manneschmidt for his assistance with mechanical property evaluations.

Keywords

Atom probe tomography (APT)
Electron backscattered diffraction (EBSD)
Mechanical properties
Oxide dispersion strengthened (ODS) alloys
Precipitation

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title = "Microstructural evaluation of a Fe-12Cr nanostructured ferritic alloy designed for impurity sequestration",

abstract = "Fast reactor fuel cladding candidate materials require proficiency in extreme environments consisting of high temperatures and irradiation doses in excess of 150 displacements per atom (dpa). Nanostructured oxide dispersion strengthened (ODS) alloys have been developed extensively for this purpose due to their notable high temperature strength, creep resistance, and irradiation resistance. However, their properties can deteriorate if interstitial impurities such as C and N are not well controlled during the fabrication process. A new Fe-12Cr nanostructured ODS alloy OFRAC (Oak Ridge Fast Reactor Advanced Fuel Cladding) with solute additions of Mo, Ti, and Nb has been developed to provide the desired properties mentioned above while simultaneously sequestering impurities within the matrix. After extrusion at 850 °C, the as-extruded microstructure consists of an average 490 nm grain size and a high number density (6.8 × 1023 m-3) of 2.2 nm diameter (Y,Ti,O) nanoclusters distributed homogeneously in the matrix. Atom probe tomography investigations suggest non-stochiometric compositions for the smallest nanoclusters. In addition, a second population of nanometer scale (Nb,Ti) rich carbonitrides is also present in the microstructure that captures the potentially detrimental C and N impurity atoms present in the matrix. Atom probe tomography results indicate elemental segregation of Cr, Mo, and Nb to grain boundaries in the as-extruded material, consistent with previous investigations of solid solution strengthening by solute additions. The ability of OFRAC to sequester impurities introduced from the powder metallurgical approach to nanostructured ferritic alloy development, compounded with its beneficial mechanical properties, makes this alloy a competitive candidate for fast reactor applications. This manuscript has been authored by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).",

keywords = "Atom probe tomography (APT), Electron backscattered diffraction (EBSD), Mechanical properties, Oxide dispersion strengthened (ODS) alloys, Precipitation",

author = "Massey, {Caleb P.} and Hoelzer, {David T.} and Seibert, {Rachel L.} and Edmondson, {Philip D.} and Anoop Kini and Baptiste Gault and Terrani, {Kurt A.} and Zinkle, {Steven J.}",

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AU - Massey, Caleb P.

AU - Hoelzer, David T.

AU - Seibert, Rachel L.

AU - Edmondson, Philip D.

AU - Kini, Anoop

AU - Gault, Baptiste

AU - Terrani, Kurt A.

AU - Zinkle, Steven J.

PY - 2019/8/15

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N2 - Fast reactor fuel cladding candidate materials require proficiency in extreme environments consisting of high temperatures and irradiation doses in excess of 150 displacements per atom (dpa). Nanostructured oxide dispersion strengthened (ODS) alloys have been developed extensively for this purpose due to their notable high temperature strength, creep resistance, and irradiation resistance. However, their properties can deteriorate if interstitial impurities such as C and N are not well controlled during the fabrication process. A new Fe-12Cr nanostructured ODS alloy OFRAC (Oak Ridge Fast Reactor Advanced Fuel Cladding) with solute additions of Mo, Ti, and Nb has been developed to provide the desired properties mentioned above while simultaneously sequestering impurities within the matrix. After extrusion at 850 °C, the as-extruded microstructure consists of an average 490 nm grain size and a high number density (6.8 × 1023 m-3) of 2.2 nm diameter (Y,Ti,O) nanoclusters distributed homogeneously in the matrix. Atom probe tomography investigations suggest non-stochiometric compositions for the smallest nanoclusters. In addition, a second population of nanometer scale (Nb,Ti) rich carbonitrides is also present in the microstructure that captures the potentially detrimental C and N impurity atoms present in the matrix. Atom probe tomography results indicate elemental segregation of Cr, Mo, and Nb to grain boundaries in the as-extruded material, consistent with previous investigations of solid solution strengthening by solute additions. The ability of OFRAC to sequester impurities introduced from the powder metallurgical approach to nanostructured ferritic alloy development, compounded with its beneficial mechanical properties, makes this alloy a competitive candidate for fast reactor applications. This manuscript has been authored by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).

AB - Fast reactor fuel cladding candidate materials require proficiency in extreme environments consisting of high temperatures and irradiation doses in excess of 150 displacements per atom (dpa). Nanostructured oxide dispersion strengthened (ODS) alloys have been developed extensively for this purpose due to their notable high temperature strength, creep resistance, and irradiation resistance. However, their properties can deteriorate if interstitial impurities such as C and N are not well controlled during the fabrication process. A new Fe-12Cr nanostructured ODS alloy OFRAC (Oak Ridge Fast Reactor Advanced Fuel Cladding) with solute additions of Mo, Ti, and Nb has been developed to provide the desired properties mentioned above while simultaneously sequestering impurities within the matrix. After extrusion at 850 °C, the as-extruded microstructure consists of an average 490 nm grain size and a high number density (6.8 × 1023 m-3) of 2.2 nm diameter (Y,Ti,O) nanoclusters distributed homogeneously in the matrix. Atom probe tomography investigations suggest non-stochiometric compositions for the smallest nanoclusters. In addition, a second population of nanometer scale (Nb,Ti) rich carbonitrides is also present in the microstructure that captures the potentially detrimental C and N impurity atoms present in the matrix. Atom probe tomography results indicate elemental segregation of Cr, Mo, and Nb to grain boundaries in the as-extruded material, consistent with previous investigations of solid solution strengthening by solute additions. The ability of OFRAC to sequester impurities introduced from the powder metallurgical approach to nanostructured ferritic alloy development, compounded with its beneficial mechanical properties, makes this alloy a competitive candidate for fast reactor applications. This manuscript has been authored by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).

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KW - Electron backscattered diffraction (EBSD)

KW - Mechanical properties

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Microstructural evaluation of a Fe-12Cr nanostructured ferritic alloy designed for impurity sequestration

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Keywords

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