On the Microstructure and Isothermal Oxidation at 800, 1200, and 1300 °C of the Al-25.5Nb-6Cr-0.5Hf (at %) Alloy
Nb-silicide-based alloys have the potential to replace Ni-based superalloys in future aero engines to enable the latter to meet environmental and performance targets. These new alloys, like the Ni-based superalloys that are currently used, will require environmental protection with a coating system...
Ausführliche Beschreibung
Autor*in: |
Ofelia Hernández-Negrete [verfasserIn] Panos Tsakiropoulos [verfasserIn] |
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Format: |
E-Artikel |
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Sprache: |
Englisch |
Erschienen: |
2019 |
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Übergeordnetes Werk: |
In: Materials - MDPI AG, 2009, 12(2019), 16, p 2531 |
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Übergeordnetes Werk: |
volume:12 ; year:2019 ; number:16, p 2531 |
Links: |
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DOI / URN: |
10.3390/ma12162531 |
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Katalog-ID: |
DOAJ054433533 |
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520 | |a Nb-silicide-based alloys have the potential to replace Ni-based superalloys in future aero engines to enable the latter to meet environmental and performance targets. These new alloys, like the Ni-based superalloys that are currently used, will require environmental protection with a coating system that should be chemically compatible with the substrate. A challenge for alloy development is to discover αAl<sub<2</sub<O<sub<3</sub< scale forming coating alloys and in particular to find out whether such alloys could be “compatible” with other coating alloys for environmental coating systems for the Nb-silicide-based alloys. This paper focuses on these challenges. The alloy Al-25.5Nb-6Cr-0.5Hf (at %) was studied in the cast and heat-treated (1400 °C) conditions and after isothermal oxidation for 100 h in air at 800, 1200 and 1300 °C. The microstructure consisted of the alloyed NbAl<sub<3</sub< and C14-NbCr<sub<2</sub< compounds, both of which were stable at least up to 1400 °C, a eutectic of the two compounds and very small volume fractions of (Cr,Al,Nb)<sub<ss</sub< and HfO<sub<2</sub<. The prior eutectic microstructure was stable at T ≤ 1200 °C and the solid solution was not stable at T < 1200 °C. At 800 °C the alloy did not pest, but exhibited external and internal oxidation, with AlNbO<sub<4</sub<, CrNbAlO<sub<4</sub<, and αAl<sub<2</sub<O<sub<3</sub< in the former and deeper oxidation along the NbAl<sub<3</sub</Laves phase boundaries in the latter At 1200 and 1300 °C there was only external oxidation and the scale consisted of two layers, the outer was (Al,Cr)NbO<sub<4</sub< intermixed with αAl<sub<2</sub<O<sub<3</sub< and the inner was continuous αAl<sub<2</sub<O<sub<3</sub<. At all three oxidation temperatures, no Nb<sub<2</sub<Al was observed below the alloy/scale interface and Hf acted as a reactive element forming HfO<sub<2</sub< that enhanced the adhesion of the scale. The alloy exhibited good correlations with αAl<sub<2</sub<O<sub<3</sub< scale forming silicide and silicide + aluminide intermetallic alloys in maps of the parameters δ (related to atomic size), Δχ (related to electronegativity), and VEC (number of valence electrons per atom filled into the valence band) that should assist the design of bond coats that do not pest and form αAl<sub<2</sub<O<sub<3</sub< in their scales. | ||
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10.3390/ma12162531 doi (DE-627)DOAJ054433533 (DE-599)DOAJe42b12772db1481f9ff08b0abd7a4680 DE-627 ger DE-627 rakwb eng TK1-9971 TA1-2040 QH201-278.5 QC120-168.85 Ofelia Hernández-Negrete verfasserin aut On the Microstructure and Isothermal Oxidation at 800, 1200, and 1300 °C of the Al-25.5Nb-6Cr-0.5Hf (at %) Alloy 2019 Text txt rdacontent Computermedien c rdamedia Online-Ressource cr rdacarrier Nb-silicide-based alloys have the potential to replace Ni-based superalloys in future aero engines to enable the latter to meet environmental and performance targets. These new alloys, like the Ni-based superalloys that are currently used, will require environmental protection with a coating system that should be chemically compatible with the substrate. A challenge for alloy development is to discover αAl<sub<2</sub<O<sub<3</sub< scale forming coating alloys and in particular to find out whether such alloys could be “compatible” with other coating alloys for environmental coating systems for the Nb-silicide-based alloys. This paper focuses on these challenges. The alloy Al-25.5Nb-6Cr-0.5Hf (at %) was studied in the cast and heat-treated (1400 °C) conditions and after isothermal oxidation for 100 h in air at 800, 1200 and 1300 °C. The microstructure consisted of the alloyed NbAl<sub<3</sub< and C14-NbCr<sub<2</sub< compounds, both of which were stable at least up to 1400 °C, a eutectic of the two compounds and very small volume fractions of (Cr,Al,Nb)<sub<ss</sub< and HfO<sub<2</sub<. The prior eutectic microstructure was stable at T ≤ 1200 °C and the solid solution was not stable at T < 1200 °C. At 800 °C the alloy did not pest, but exhibited external and internal oxidation, with AlNbO<sub<4</sub<, CrNbAlO<sub<4</sub<, and αAl<sub<2</sub<O<sub<3</sub< in the former and deeper oxidation along the NbAl<sub<3</sub</Laves phase boundaries in the latter At 1200 and 1300 °C there was only external oxidation and the scale consisted of two layers, the outer was (Al,Cr)NbO<sub<4</sub< intermixed with αAl<sub<2</sub<O<sub<3</sub< and the inner was continuous αAl<sub<2</sub<O<sub<3</sub<. At all three oxidation temperatures, no Nb<sub<2</sub<Al was observed below the alloy/scale interface and Hf acted as a reactive element forming HfO<sub<2</sub< that enhanced the adhesion of the scale. The alloy exhibited good correlations with αAl<sub<2</sub<O<sub<3</sub< scale forming silicide and silicide + aluminide intermetallic alloys in maps of the parameters δ (related to atomic size), Δχ (related to electronegativity), and VEC (number of valence electrons per atom filled into the valence band) that should assist the design of bond coats that do not pest and form αAl<sub<2</sub<O<sub<3</sub< in their scales. coatings intermetallics aluminides pest oxidation high temperature oxidation Nb-silicide-based alloys high entropy alloys complex concentrated alloys Technology T Electrical engineering. Electronics. Nuclear engineering Engineering (General). Civil engineering (General) Microscopy Descriptive and experimental mechanics Panos Tsakiropoulos verfasserin aut In Materials MDPI AG, 2009 12(2019), 16, p 2531 (DE-627)595712649 (DE-600)2487261-1 19961944 nnns volume:12 year:2019 number:16, p 2531 https://doi.org/10.3390/ma12162531 kostenfrei https://doaj.org/article/e42b12772db1481f9ff08b0abd7a4680 kostenfrei https://www.mdpi.com/1996-1944/12/16/2531 kostenfrei https://doaj.org/toc/1996-1944 Journal toc kostenfrei GBV_USEFLAG_A SYSFLAG_A GBV_DOAJ GBV_ILN_11 GBV_ILN_20 GBV_ILN_22 GBV_ILN_23 GBV_ILN_24 GBV_ILN_39 GBV_ILN_40 GBV_ILN_60 GBV_ILN_62 GBV_ILN_63 GBV_ILN_65 GBV_ILN_69 GBV_ILN_70 GBV_ILN_73 GBV_ILN_95 GBV_ILN_105 GBV_ILN_110 GBV_ILN_151 GBV_ILN_161 GBV_ILN_170 GBV_ILN_206 GBV_ILN_213 GBV_ILN_230 GBV_ILN_285 GBV_ILN_293 GBV_ILN_370 GBV_ILN_602 GBV_ILN_2005 GBV_ILN_2009 GBV_ILN_2011 GBV_ILN_2014 GBV_ILN_2055 GBV_ILN_2057 GBV_ILN_2108 GBV_ILN_2111 GBV_ILN_2119 GBV_ILN_4012 GBV_ILN_4037 GBV_ILN_4112 GBV_ILN_4125 GBV_ILN_4126 GBV_ILN_4249 GBV_ILN_4305 GBV_ILN_4306 GBV_ILN_4307 GBV_ILN_4313 GBV_ILN_4322 GBV_ILN_4323 GBV_ILN_4324 GBV_ILN_4325 GBV_ILN_4335 GBV_ILN_4338 GBV_ILN_4367 GBV_ILN_4700 AR 12 2019 16, p 2531 |
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10.3390/ma12162531 doi (DE-627)DOAJ054433533 (DE-599)DOAJe42b12772db1481f9ff08b0abd7a4680 DE-627 ger DE-627 rakwb eng TK1-9971 TA1-2040 QH201-278.5 QC120-168.85 Ofelia Hernández-Negrete verfasserin aut On the Microstructure and Isothermal Oxidation at 800, 1200, and 1300 °C of the Al-25.5Nb-6Cr-0.5Hf (at %) Alloy 2019 Text txt rdacontent Computermedien c rdamedia Online-Ressource cr rdacarrier Nb-silicide-based alloys have the potential to replace Ni-based superalloys in future aero engines to enable the latter to meet environmental and performance targets. These new alloys, like the Ni-based superalloys that are currently used, will require environmental protection with a coating system that should be chemically compatible with the substrate. A challenge for alloy development is to discover αAl<sub<2</sub<O<sub<3</sub< scale forming coating alloys and in particular to find out whether such alloys could be “compatible” with other coating alloys for environmental coating systems for the Nb-silicide-based alloys. This paper focuses on these challenges. The alloy Al-25.5Nb-6Cr-0.5Hf (at %) was studied in the cast and heat-treated (1400 °C) conditions and after isothermal oxidation for 100 h in air at 800, 1200 and 1300 °C. The microstructure consisted of the alloyed NbAl<sub<3</sub< and C14-NbCr<sub<2</sub< compounds, both of which were stable at least up to 1400 °C, a eutectic of the two compounds and very small volume fractions of (Cr,Al,Nb)<sub<ss</sub< and HfO<sub<2</sub<. The prior eutectic microstructure was stable at T ≤ 1200 °C and the solid solution was not stable at T < 1200 °C. At 800 °C the alloy did not pest, but exhibited external and internal oxidation, with AlNbO<sub<4</sub<, CrNbAlO<sub<4</sub<, and αAl<sub<2</sub<O<sub<3</sub< in the former and deeper oxidation along the NbAl<sub<3</sub</Laves phase boundaries in the latter At 1200 and 1300 °C there was only external oxidation and the scale consisted of two layers, the outer was (Al,Cr)NbO<sub<4</sub< intermixed with αAl<sub<2</sub<O<sub<3</sub< and the inner was continuous αAl<sub<2</sub<O<sub<3</sub<. At all three oxidation temperatures, no Nb<sub<2</sub<Al was observed below the alloy/scale interface and Hf acted as a reactive element forming HfO<sub<2</sub< that enhanced the adhesion of the scale. The alloy exhibited good correlations with αAl<sub<2</sub<O<sub<3</sub< scale forming silicide and silicide + aluminide intermetallic alloys in maps of the parameters δ (related to atomic size), Δχ (related to electronegativity), and VEC (number of valence electrons per atom filled into the valence band) that should assist the design of bond coats that do not pest and form αAl<sub<2</sub<O<sub<3</sub< in their scales. coatings intermetallics aluminides pest oxidation high temperature oxidation Nb-silicide-based alloys high entropy alloys complex concentrated alloys Technology T Electrical engineering. Electronics. Nuclear engineering Engineering (General). Civil engineering (General) Microscopy Descriptive and experimental mechanics Panos Tsakiropoulos verfasserin aut In Materials MDPI AG, 2009 12(2019), 16, p 2531 (DE-627)595712649 (DE-600)2487261-1 19961944 nnns volume:12 year:2019 number:16, p 2531 https://doi.org/10.3390/ma12162531 kostenfrei https://doaj.org/article/e42b12772db1481f9ff08b0abd7a4680 kostenfrei https://www.mdpi.com/1996-1944/12/16/2531 kostenfrei https://doaj.org/toc/1996-1944 Journal toc kostenfrei GBV_USEFLAG_A SYSFLAG_A GBV_DOAJ GBV_ILN_11 GBV_ILN_20 GBV_ILN_22 GBV_ILN_23 GBV_ILN_24 GBV_ILN_39 GBV_ILN_40 GBV_ILN_60 GBV_ILN_62 GBV_ILN_63 GBV_ILN_65 GBV_ILN_69 GBV_ILN_70 GBV_ILN_73 GBV_ILN_95 GBV_ILN_105 GBV_ILN_110 GBV_ILN_151 GBV_ILN_161 GBV_ILN_170 GBV_ILN_206 GBV_ILN_213 GBV_ILN_230 GBV_ILN_285 GBV_ILN_293 GBV_ILN_370 GBV_ILN_602 GBV_ILN_2005 GBV_ILN_2009 GBV_ILN_2011 GBV_ILN_2014 GBV_ILN_2055 GBV_ILN_2057 GBV_ILN_2108 GBV_ILN_2111 GBV_ILN_2119 GBV_ILN_4012 GBV_ILN_4037 GBV_ILN_4112 GBV_ILN_4125 GBV_ILN_4126 GBV_ILN_4249 GBV_ILN_4305 GBV_ILN_4306 GBV_ILN_4307 GBV_ILN_4313 GBV_ILN_4322 GBV_ILN_4323 GBV_ILN_4324 GBV_ILN_4325 GBV_ILN_4335 GBV_ILN_4338 GBV_ILN_4367 GBV_ILN_4700 AR 12 2019 16, p 2531 |
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10.3390/ma12162531 doi (DE-627)DOAJ054433533 (DE-599)DOAJe42b12772db1481f9ff08b0abd7a4680 DE-627 ger DE-627 rakwb eng TK1-9971 TA1-2040 QH201-278.5 QC120-168.85 Ofelia Hernández-Negrete verfasserin aut On the Microstructure and Isothermal Oxidation at 800, 1200, and 1300 °C of the Al-25.5Nb-6Cr-0.5Hf (at %) Alloy 2019 Text txt rdacontent Computermedien c rdamedia Online-Ressource cr rdacarrier Nb-silicide-based alloys have the potential to replace Ni-based superalloys in future aero engines to enable the latter to meet environmental and performance targets. These new alloys, like the Ni-based superalloys that are currently used, will require environmental protection with a coating system that should be chemically compatible with the substrate. A challenge for alloy development is to discover αAl<sub<2</sub<O<sub<3</sub< scale forming coating alloys and in particular to find out whether such alloys could be “compatible” with other coating alloys for environmental coating systems for the Nb-silicide-based alloys. This paper focuses on these challenges. The alloy Al-25.5Nb-6Cr-0.5Hf (at %) was studied in the cast and heat-treated (1400 °C) conditions and after isothermal oxidation for 100 h in air at 800, 1200 and 1300 °C. The microstructure consisted of the alloyed NbAl<sub<3</sub< and C14-NbCr<sub<2</sub< compounds, both of which were stable at least up to 1400 °C, a eutectic of the two compounds and very small volume fractions of (Cr,Al,Nb)<sub<ss</sub< and HfO<sub<2</sub<. The prior eutectic microstructure was stable at T ≤ 1200 °C and the solid solution was not stable at T < 1200 °C. At 800 °C the alloy did not pest, but exhibited external and internal oxidation, with AlNbO<sub<4</sub<, CrNbAlO<sub<4</sub<, and αAl<sub<2</sub<O<sub<3</sub< in the former and deeper oxidation along the NbAl<sub<3</sub</Laves phase boundaries in the latter At 1200 and 1300 °C there was only external oxidation and the scale consisted of two layers, the outer was (Al,Cr)NbO<sub<4</sub< intermixed with αAl<sub<2</sub<O<sub<3</sub< and the inner was continuous αAl<sub<2</sub<O<sub<3</sub<. At all three oxidation temperatures, no Nb<sub<2</sub<Al was observed below the alloy/scale interface and Hf acted as a reactive element forming HfO<sub<2</sub< that enhanced the adhesion of the scale. The alloy exhibited good correlations with αAl<sub<2</sub<O<sub<3</sub< scale forming silicide and silicide + aluminide intermetallic alloys in maps of the parameters δ (related to atomic size), Δχ (related to electronegativity), and VEC (number of valence electrons per atom filled into the valence band) that should assist the design of bond coats that do not pest and form αAl<sub<2</sub<O<sub<3</sub< in their scales. coatings intermetallics aluminides pest oxidation high temperature oxidation Nb-silicide-based alloys high entropy alloys complex concentrated alloys Technology T Electrical engineering. Electronics. Nuclear engineering Engineering (General). Civil engineering (General) Microscopy Descriptive and experimental mechanics Panos Tsakiropoulos verfasserin aut In Materials MDPI AG, 2009 12(2019), 16, p 2531 (DE-627)595712649 (DE-600)2487261-1 19961944 nnns volume:12 year:2019 number:16, p 2531 https://doi.org/10.3390/ma12162531 kostenfrei https://doaj.org/article/e42b12772db1481f9ff08b0abd7a4680 kostenfrei https://www.mdpi.com/1996-1944/12/16/2531 kostenfrei https://doaj.org/toc/1996-1944 Journal toc kostenfrei GBV_USEFLAG_A SYSFLAG_A GBV_DOAJ GBV_ILN_11 GBV_ILN_20 GBV_ILN_22 GBV_ILN_23 GBV_ILN_24 GBV_ILN_39 GBV_ILN_40 GBV_ILN_60 GBV_ILN_62 GBV_ILN_63 GBV_ILN_65 GBV_ILN_69 GBV_ILN_70 GBV_ILN_73 GBV_ILN_95 GBV_ILN_105 GBV_ILN_110 GBV_ILN_151 GBV_ILN_161 GBV_ILN_170 GBV_ILN_206 GBV_ILN_213 GBV_ILN_230 GBV_ILN_285 GBV_ILN_293 GBV_ILN_370 GBV_ILN_602 GBV_ILN_2005 GBV_ILN_2009 GBV_ILN_2011 GBV_ILN_2014 GBV_ILN_2055 GBV_ILN_2057 GBV_ILN_2108 GBV_ILN_2111 GBV_ILN_2119 GBV_ILN_4012 GBV_ILN_4037 GBV_ILN_4112 GBV_ILN_4125 GBV_ILN_4126 GBV_ILN_4249 GBV_ILN_4305 GBV_ILN_4306 GBV_ILN_4307 GBV_ILN_4313 GBV_ILN_4322 GBV_ILN_4323 GBV_ILN_4324 GBV_ILN_4325 GBV_ILN_4335 GBV_ILN_4338 GBV_ILN_4367 GBV_ILN_4700 AR 12 2019 16, p 2531 |
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10.3390/ma12162531 doi (DE-627)DOAJ054433533 (DE-599)DOAJe42b12772db1481f9ff08b0abd7a4680 DE-627 ger DE-627 rakwb eng TK1-9971 TA1-2040 QH201-278.5 QC120-168.85 Ofelia Hernández-Negrete verfasserin aut On the Microstructure and Isothermal Oxidation at 800, 1200, and 1300 °C of the Al-25.5Nb-6Cr-0.5Hf (at %) Alloy 2019 Text txt rdacontent Computermedien c rdamedia Online-Ressource cr rdacarrier Nb-silicide-based alloys have the potential to replace Ni-based superalloys in future aero engines to enable the latter to meet environmental and performance targets. These new alloys, like the Ni-based superalloys that are currently used, will require environmental protection with a coating system that should be chemically compatible with the substrate. A challenge for alloy development is to discover αAl<sub<2</sub<O<sub<3</sub< scale forming coating alloys and in particular to find out whether such alloys could be “compatible” with other coating alloys for environmental coating systems for the Nb-silicide-based alloys. This paper focuses on these challenges. The alloy Al-25.5Nb-6Cr-0.5Hf (at %) was studied in the cast and heat-treated (1400 °C) conditions and after isothermal oxidation for 100 h in air at 800, 1200 and 1300 °C. The microstructure consisted of the alloyed NbAl<sub<3</sub< and C14-NbCr<sub<2</sub< compounds, both of which were stable at least up to 1400 °C, a eutectic of the two compounds and very small volume fractions of (Cr,Al,Nb)<sub<ss</sub< and HfO<sub<2</sub<. The prior eutectic microstructure was stable at T ≤ 1200 °C and the solid solution was not stable at T < 1200 °C. At 800 °C the alloy did not pest, but exhibited external and internal oxidation, with AlNbO<sub<4</sub<, CrNbAlO<sub<4</sub<, and αAl<sub<2</sub<O<sub<3</sub< in the former and deeper oxidation along the NbAl<sub<3</sub</Laves phase boundaries in the latter At 1200 and 1300 °C there was only external oxidation and the scale consisted of two layers, the outer was (Al,Cr)NbO<sub<4</sub< intermixed with αAl<sub<2</sub<O<sub<3</sub< and the inner was continuous αAl<sub<2</sub<O<sub<3</sub<. At all three oxidation temperatures, no Nb<sub<2</sub<Al was observed below the alloy/scale interface and Hf acted as a reactive element forming HfO<sub<2</sub< that enhanced the adhesion of the scale. The alloy exhibited good correlations with αAl<sub<2</sub<O<sub<3</sub< scale forming silicide and silicide + aluminide intermetallic alloys in maps of the parameters δ (related to atomic size), Δχ (related to electronegativity), and VEC (number of valence electrons per atom filled into the valence band) that should assist the design of bond coats that do not pest and form αAl<sub<2</sub<O<sub<3</sub< in their scales. coatings intermetallics aluminides pest oxidation high temperature oxidation Nb-silicide-based alloys high entropy alloys complex concentrated alloys Technology T Electrical engineering. Electronics. Nuclear engineering Engineering (General). Civil engineering (General) Microscopy Descriptive and experimental mechanics Panos Tsakiropoulos verfasserin aut In Materials MDPI AG, 2009 12(2019), 16, p 2531 (DE-627)595712649 (DE-600)2487261-1 19961944 nnns volume:12 year:2019 number:16, p 2531 https://doi.org/10.3390/ma12162531 kostenfrei https://doaj.org/article/e42b12772db1481f9ff08b0abd7a4680 kostenfrei https://www.mdpi.com/1996-1944/12/16/2531 kostenfrei https://doaj.org/toc/1996-1944 Journal toc kostenfrei GBV_USEFLAG_A SYSFLAG_A GBV_DOAJ GBV_ILN_11 GBV_ILN_20 GBV_ILN_22 GBV_ILN_23 GBV_ILN_24 GBV_ILN_39 GBV_ILN_40 GBV_ILN_60 GBV_ILN_62 GBV_ILN_63 GBV_ILN_65 GBV_ILN_69 GBV_ILN_70 GBV_ILN_73 GBV_ILN_95 GBV_ILN_105 GBV_ILN_110 GBV_ILN_151 GBV_ILN_161 GBV_ILN_170 GBV_ILN_206 GBV_ILN_213 GBV_ILN_230 GBV_ILN_285 GBV_ILN_293 GBV_ILN_370 GBV_ILN_602 GBV_ILN_2005 GBV_ILN_2009 GBV_ILN_2011 GBV_ILN_2014 GBV_ILN_2055 GBV_ILN_2057 GBV_ILN_2108 GBV_ILN_2111 GBV_ILN_2119 GBV_ILN_4012 GBV_ILN_4037 GBV_ILN_4112 GBV_ILN_4125 GBV_ILN_4126 GBV_ILN_4249 GBV_ILN_4305 GBV_ILN_4306 GBV_ILN_4307 GBV_ILN_4313 GBV_ILN_4322 GBV_ILN_4323 GBV_ILN_4324 GBV_ILN_4325 GBV_ILN_4335 GBV_ILN_4338 GBV_ILN_4367 GBV_ILN_4700 AR 12 2019 16, p 2531 |
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10.3390/ma12162531 doi (DE-627)DOAJ054433533 (DE-599)DOAJe42b12772db1481f9ff08b0abd7a4680 DE-627 ger DE-627 rakwb eng TK1-9971 TA1-2040 QH201-278.5 QC120-168.85 Ofelia Hernández-Negrete verfasserin aut On the Microstructure and Isothermal Oxidation at 800, 1200, and 1300 °C of the Al-25.5Nb-6Cr-0.5Hf (at %) Alloy 2019 Text txt rdacontent Computermedien c rdamedia Online-Ressource cr rdacarrier Nb-silicide-based alloys have the potential to replace Ni-based superalloys in future aero engines to enable the latter to meet environmental and performance targets. These new alloys, like the Ni-based superalloys that are currently used, will require environmental protection with a coating system that should be chemically compatible with the substrate. A challenge for alloy development is to discover αAl<sub<2</sub<O<sub<3</sub< scale forming coating alloys and in particular to find out whether such alloys could be “compatible” with other coating alloys for environmental coating systems for the Nb-silicide-based alloys. This paper focuses on these challenges. The alloy Al-25.5Nb-6Cr-0.5Hf (at %) was studied in the cast and heat-treated (1400 °C) conditions and after isothermal oxidation for 100 h in air at 800, 1200 and 1300 °C. The microstructure consisted of the alloyed NbAl<sub<3</sub< and C14-NbCr<sub<2</sub< compounds, both of which were stable at least up to 1400 °C, a eutectic of the two compounds and very small volume fractions of (Cr,Al,Nb)<sub<ss</sub< and HfO<sub<2</sub<. The prior eutectic microstructure was stable at T ≤ 1200 °C and the solid solution was not stable at T < 1200 °C. At 800 °C the alloy did not pest, but exhibited external and internal oxidation, with AlNbO<sub<4</sub<, CrNbAlO<sub<4</sub<, and αAl<sub<2</sub<O<sub<3</sub< in the former and deeper oxidation along the NbAl<sub<3</sub</Laves phase boundaries in the latter At 1200 and 1300 °C there was only external oxidation and the scale consisted of two layers, the outer was (Al,Cr)NbO<sub<4</sub< intermixed with αAl<sub<2</sub<O<sub<3</sub< and the inner was continuous αAl<sub<2</sub<O<sub<3</sub<. At all three oxidation temperatures, no Nb<sub<2</sub<Al was observed below the alloy/scale interface and Hf acted as a reactive element forming HfO<sub<2</sub< that enhanced the adhesion of the scale. The alloy exhibited good correlations with αAl<sub<2</sub<O<sub<3</sub< scale forming silicide and silicide + aluminide intermetallic alloys in maps of the parameters δ (related to atomic size), Δχ (related to electronegativity), and VEC (number of valence electrons per atom filled into the valence band) that should assist the design of bond coats that do not pest and form αAl<sub<2</sub<O<sub<3</sub< in their scales. coatings intermetallics aluminides pest oxidation high temperature oxidation Nb-silicide-based alloys high entropy alloys complex concentrated alloys Technology T Electrical engineering. Electronics. Nuclear engineering Engineering (General). Civil engineering (General) Microscopy Descriptive and experimental mechanics Panos Tsakiropoulos verfasserin aut In Materials MDPI AG, 2009 12(2019), 16, p 2531 (DE-627)595712649 (DE-600)2487261-1 19961944 nnns volume:12 year:2019 number:16, p 2531 https://doi.org/10.3390/ma12162531 kostenfrei https://doaj.org/article/e42b12772db1481f9ff08b0abd7a4680 kostenfrei https://www.mdpi.com/1996-1944/12/16/2531 kostenfrei https://doaj.org/toc/1996-1944 Journal toc kostenfrei GBV_USEFLAG_A SYSFLAG_A GBV_DOAJ GBV_ILN_11 GBV_ILN_20 GBV_ILN_22 GBV_ILN_23 GBV_ILN_24 GBV_ILN_39 GBV_ILN_40 GBV_ILN_60 GBV_ILN_62 GBV_ILN_63 GBV_ILN_65 GBV_ILN_69 GBV_ILN_70 GBV_ILN_73 GBV_ILN_95 GBV_ILN_105 GBV_ILN_110 GBV_ILN_151 GBV_ILN_161 GBV_ILN_170 GBV_ILN_206 GBV_ILN_213 GBV_ILN_230 GBV_ILN_285 GBV_ILN_293 GBV_ILN_370 GBV_ILN_602 GBV_ILN_2005 GBV_ILN_2009 GBV_ILN_2011 GBV_ILN_2014 GBV_ILN_2055 GBV_ILN_2057 GBV_ILN_2108 GBV_ILN_2111 GBV_ILN_2119 GBV_ILN_4012 GBV_ILN_4037 GBV_ILN_4112 GBV_ILN_4125 GBV_ILN_4126 GBV_ILN_4249 GBV_ILN_4305 GBV_ILN_4306 GBV_ILN_4307 GBV_ILN_4313 GBV_ILN_4322 GBV_ILN_4323 GBV_ILN_4324 GBV_ILN_4325 GBV_ILN_4335 GBV_ILN_4338 GBV_ILN_4367 GBV_ILN_4700 AR 12 2019 16, p 2531 |
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Ofelia Hernández-Negrete |
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Ofelia Hernández-Negrete misc TK1-9971 misc TA1-2040 misc QH201-278.5 misc QC120-168.85 misc coatings misc intermetallics misc aluminides misc pest oxidation misc high temperature oxidation misc Nb-silicide-based alloys misc high entropy alloys misc complex concentrated alloys misc Technology misc T misc Electrical engineering. Electronics. Nuclear engineering misc Engineering (General). Civil engineering (General) misc Microscopy misc Descriptive and experimental mechanics On the Microstructure and Isothermal Oxidation at 800, 1200, and 1300 °C of the Al-25.5Nb-6Cr-0.5Hf (at %) Alloy |
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TK1-9971 TA1-2040 QH201-278.5 QC120-168.85 On the Microstructure and Isothermal Oxidation at 800, 1200, and 1300 °C of the Al-25.5Nb-6Cr-0.5Hf (at %) Alloy coatings intermetallics aluminides pest oxidation high temperature oxidation Nb-silicide-based alloys high entropy alloys complex concentrated alloys |
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misc TK1-9971 misc TA1-2040 misc QH201-278.5 misc QC120-168.85 misc coatings misc intermetallics misc aluminides misc pest oxidation misc high temperature oxidation misc Nb-silicide-based alloys misc high entropy alloys misc complex concentrated alloys misc Technology misc T misc Electrical engineering. Electronics. Nuclear engineering misc Engineering (General). Civil engineering (General) misc Microscopy misc Descriptive and experimental mechanics |
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On the Microstructure and Isothermal Oxidation at 800, 1200, and 1300 °C of the Al-25.5Nb-6Cr-0.5Hf (at %) Alloy |
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On the Microstructure and Isothermal Oxidation at 800, 1200, and 1300 °C of the Al-25.5Nb-6Cr-0.5Hf (at %) Alloy |
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Ofelia Hernández-Negrete |
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on the microstructure and isothermal oxidation at 800, 1200, and 1300 °c of the al-25.5nb-6cr-0.5hf (at %) alloy |
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TK1-9971 |
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On the Microstructure and Isothermal Oxidation at 800, 1200, and 1300 °C of the Al-25.5Nb-6Cr-0.5Hf (at %) Alloy |
abstract |
Nb-silicide-based alloys have the potential to replace Ni-based superalloys in future aero engines to enable the latter to meet environmental and performance targets. These new alloys, like the Ni-based superalloys that are currently used, will require environmental protection with a coating system that should be chemically compatible with the substrate. A challenge for alloy development is to discover αAl<sub<2</sub<O<sub<3</sub< scale forming coating alloys and in particular to find out whether such alloys could be “compatible” with other coating alloys for environmental coating systems for the Nb-silicide-based alloys. This paper focuses on these challenges. The alloy Al-25.5Nb-6Cr-0.5Hf (at %) was studied in the cast and heat-treated (1400 °C) conditions and after isothermal oxidation for 100 h in air at 800, 1200 and 1300 °C. The microstructure consisted of the alloyed NbAl<sub<3</sub< and C14-NbCr<sub<2</sub< compounds, both of which were stable at least up to 1400 °C, a eutectic of the two compounds and very small volume fractions of (Cr,Al,Nb)<sub<ss</sub< and HfO<sub<2</sub<. The prior eutectic microstructure was stable at T ≤ 1200 °C and the solid solution was not stable at T < 1200 °C. At 800 °C the alloy did not pest, but exhibited external and internal oxidation, with AlNbO<sub<4</sub<, CrNbAlO<sub<4</sub<, and αAl<sub<2</sub<O<sub<3</sub< in the former and deeper oxidation along the NbAl<sub<3</sub</Laves phase boundaries in the latter At 1200 and 1300 °C there was only external oxidation and the scale consisted of two layers, the outer was (Al,Cr)NbO<sub<4</sub< intermixed with αAl<sub<2</sub<O<sub<3</sub< and the inner was continuous αAl<sub<2</sub<O<sub<3</sub<. At all three oxidation temperatures, no Nb<sub<2</sub<Al was observed below the alloy/scale interface and Hf acted as a reactive element forming HfO<sub<2</sub< that enhanced the adhesion of the scale. The alloy exhibited good correlations with αAl<sub<2</sub<O<sub<3</sub< scale forming silicide and silicide + aluminide intermetallic alloys in maps of the parameters δ (related to atomic size), Δχ (related to electronegativity), and VEC (number of valence electrons per atom filled into the valence band) that should assist the design of bond coats that do not pest and form αAl<sub<2</sub<O<sub<3</sub< in their scales. |
abstractGer |
Nb-silicide-based alloys have the potential to replace Ni-based superalloys in future aero engines to enable the latter to meet environmental and performance targets. These new alloys, like the Ni-based superalloys that are currently used, will require environmental protection with a coating system that should be chemically compatible with the substrate. A challenge for alloy development is to discover αAl<sub<2</sub<O<sub<3</sub< scale forming coating alloys and in particular to find out whether such alloys could be “compatible” with other coating alloys for environmental coating systems for the Nb-silicide-based alloys. This paper focuses on these challenges. The alloy Al-25.5Nb-6Cr-0.5Hf (at %) was studied in the cast and heat-treated (1400 °C) conditions and after isothermal oxidation for 100 h in air at 800, 1200 and 1300 °C. The microstructure consisted of the alloyed NbAl<sub<3</sub< and C14-NbCr<sub<2</sub< compounds, both of which were stable at least up to 1400 °C, a eutectic of the two compounds and very small volume fractions of (Cr,Al,Nb)<sub<ss</sub< and HfO<sub<2</sub<. The prior eutectic microstructure was stable at T ≤ 1200 °C and the solid solution was not stable at T < 1200 °C. At 800 °C the alloy did not pest, but exhibited external and internal oxidation, with AlNbO<sub<4</sub<, CrNbAlO<sub<4</sub<, and αAl<sub<2</sub<O<sub<3</sub< in the former and deeper oxidation along the NbAl<sub<3</sub</Laves phase boundaries in the latter At 1200 and 1300 °C there was only external oxidation and the scale consisted of two layers, the outer was (Al,Cr)NbO<sub<4</sub< intermixed with αAl<sub<2</sub<O<sub<3</sub< and the inner was continuous αAl<sub<2</sub<O<sub<3</sub<. At all three oxidation temperatures, no Nb<sub<2</sub<Al was observed below the alloy/scale interface and Hf acted as a reactive element forming HfO<sub<2</sub< that enhanced the adhesion of the scale. The alloy exhibited good correlations with αAl<sub<2</sub<O<sub<3</sub< scale forming silicide and silicide + aluminide intermetallic alloys in maps of the parameters δ (related to atomic size), Δχ (related to electronegativity), and VEC (number of valence electrons per atom filled into the valence band) that should assist the design of bond coats that do not pest and form αAl<sub<2</sub<O<sub<3</sub< in their scales. |
abstract_unstemmed |
Nb-silicide-based alloys have the potential to replace Ni-based superalloys in future aero engines to enable the latter to meet environmental and performance targets. These new alloys, like the Ni-based superalloys that are currently used, will require environmental protection with a coating system that should be chemically compatible with the substrate. A challenge for alloy development is to discover αAl<sub<2</sub<O<sub<3</sub< scale forming coating alloys and in particular to find out whether such alloys could be “compatible” with other coating alloys for environmental coating systems for the Nb-silicide-based alloys. This paper focuses on these challenges. The alloy Al-25.5Nb-6Cr-0.5Hf (at %) was studied in the cast and heat-treated (1400 °C) conditions and after isothermal oxidation for 100 h in air at 800, 1200 and 1300 °C. The microstructure consisted of the alloyed NbAl<sub<3</sub< and C14-NbCr<sub<2</sub< compounds, both of which were stable at least up to 1400 °C, a eutectic of the two compounds and very small volume fractions of (Cr,Al,Nb)<sub<ss</sub< and HfO<sub<2</sub<. The prior eutectic microstructure was stable at T ≤ 1200 °C and the solid solution was not stable at T < 1200 °C. At 800 °C the alloy did not pest, but exhibited external and internal oxidation, with AlNbO<sub<4</sub<, CrNbAlO<sub<4</sub<, and αAl<sub<2</sub<O<sub<3</sub< in the former and deeper oxidation along the NbAl<sub<3</sub</Laves phase boundaries in the latter At 1200 and 1300 °C there was only external oxidation and the scale consisted of two layers, the outer was (Al,Cr)NbO<sub<4</sub< intermixed with αAl<sub<2</sub<O<sub<3</sub< and the inner was continuous αAl<sub<2</sub<O<sub<3</sub<. At all three oxidation temperatures, no Nb<sub<2</sub<Al was observed below the alloy/scale interface and Hf acted as a reactive element forming HfO<sub<2</sub< that enhanced the adhesion of the scale. The alloy exhibited good correlations with αAl<sub<2</sub<O<sub<3</sub< scale forming silicide and silicide + aluminide intermetallic alloys in maps of the parameters δ (related to atomic size), Δχ (related to electronegativity), and VEC (number of valence electrons per atom filled into the valence band) that should assist the design of bond coats that do not pest and form αAl<sub<2</sub<O<sub<3</sub< in their scales. |
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On the Microstructure and Isothermal Oxidation at 800, 1200, and 1300 °C of the Al-25.5Nb-6Cr-0.5Hf (at %) Alloy |
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