The ternary Cr–Al–Nb phase diagram: Experimental investigations of isothermal sections at 1150, 1300 and 1450°C

Prymak, Oleg; Stein, Frank

doi:10.1016/j.jallcom.2011.10.053

Cited by 14 publications

(10 citation statements)

References 41 publications

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“…The solubility of Cr in NbAl 3 in the cast and heat-treated conditions was in the range 0.7 to 1.2 at % Cr and in the NbAl 3 phase in the eutectic respectively, in the ranges 2.2–4.9 at % Cr, and 0.6–0.9 at % Cr in the cast and the heat-treated alloy. These values were consistent with the solubility values reported in reference [44,74]. Mahdouk and Gachon [75] reported up to 10.8 at % Cr solubility in NbAl 3 at 1000 °C, a value considerable higher than the above.…”

Section: Discussionsupporting

confidence: 92%

“…The Laves phase in OHC3 was the hexagonal C14 type (Figure 2) with average Al content in the range 43 to 46 at % Al, in agreement with [50,74]. Doychak and Hebsur [44] reported the formation of a ternary compound AlNbCr in NbAl 3 + xCr (x = 1.2, 2.4, 4.8, 6.8 at %) alloys in which the concentrations of Al and Cr respectively were in the ranges 40.1–46.1 at % Al and 23.7–28.4 at % Cr, i.e., the AlNbCr phase in reference [44] had Al + Cr in the range 66.9 to 74.2 (average 69.8 at %), compared with Al + Cr in the range 65 to 68 (average 65.9 at %) for the C14-Nb(Cr,Al) 2 reported in reference [74] and the average Al + Cr = 66.6 at % for the Laves phase in OHC3. Doychak and Hebsur [44] gave the space group of AlCrNb as P6 3 /mmm.…”

Section: Discussionsupporting

confidence: 68%

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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

Hernández-Negrete

Tsakiropoulos

2019

Materials

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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 αAl2O3 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 NbAl3 and C14-NbCr2 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)ss and HfO2. 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 AlNbO4, CrNbAlO4, and αAl2O3 in the former and deeper oxidation along the NbAl3/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)NbO4 intermixed with αAl2O3 and the inner was continuous αAl2O3. At all three oxidation temperatures, no Nb2Al was observed below the alloy/scale interface and Hf acted as a reactive element forming HfO2 that enhanced the adhesion of the scale. The alloy exhibited good correlations with αAl2O3 scale forming silicide and silicide + aluminide intermetallic alloys in maps of the parameters (related to atomic size), (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 αAl2O3 in their scales.

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Section: Discussionsupporting

confidence: 92%

Section: Discussionsupporting

confidence: 68%

On the Microstructure and Isothermal Oxidation at 800, 1200, and 1300 °C of the Al-25.5Nb-6Cr-0.5Hf (at %) Alloy

Hernández-Negrete

Tsakiropoulos

2019

Materials

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“…small additions of Fe stabilize the C14-Fe 2 Nb Laves phase. It is a common phenomenon that small additions of a third elements result in a polytype change; see for example the effect of Al in Cr-Nb-Al [6,14].…”

Section: A Ternary Solid Solutions Of C15-and C14-type Laves-phasesmentioning

confidence: 99%

“…The two structure types, cubic C15 and hexagonal C14, are closely related [6,14,15]. The change of structure polytype is due to an increase of the electron concentration by adding Fe that makes C14…”

Section: A Ternary Solid Solutions Of C15-and C14-type Laves-phasesmentioning

confidence: 99%

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The Cr–Fe–Nb ternary system: Experimental isothermal sections at 700 °C, 1050 °C and 1350 °C

Jacob

Schmetterer

Grüner

et al. 2015

Journal of Alloys and Compounds

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A study on the influence of Mo, Al and Si additions on the microstructure of annealed dual phase Cr–Ta alloys

Bhowmik

Stone

2013

J Mater Sci

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The ternary Cr–Al–Nb phase diagram: Experimental investigations of isothermal sections at 1150, 1300 and 1450°C

Cited by 14 publications

References 41 publications

On the Microstructure and Isothermal Oxidation at 800, 1200, and 1300 °C of the Al-25.5Nb-6Cr-0.5Hf (at %) Alloy

On the Microstructure and Isothermal Oxidation at 800, 1200, and 1300 °C of the Al-25.5Nb-6Cr-0.5Hf (at %) Alloy

The Cr–Fe–Nb ternary system: Experimental isothermal sections at 700 °C, 1050 °C and 1350 °C

A study on the influence of Mo, Al and Si additions on the microstructure of annealed dual phase Cr–Ta alloys

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