Influences of Al content and secondary phase of Mo5(Si,Al)3 on the oxidation resistance of Al-rich Mo(Si,Al)2-base composites

Tabaru, Tatsuo; Shobu, Kazuhisa; Hirai, Hisatoshi; Hanada, Shuji

doi:10.1016/s0966-9795(03)00072-4

Cited by 41 publications

(35 citation statements)

References 26 publications

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“…[21] Hence, much interest and effort have been addressed to date regarding this material and its composites. [25][26][27][28][29][30][31][32][33] Mo(Si,Al) 2 has a wide compositional variety with respect to its substitution ratio of Al for Si, x, and the crystal structure changes from the C11 b (in strukturbericht designation) structure in the range of x Յ 0.044 to C40 in 0.130 Յ x Յ 0.456, and further to C54 in 0.580 Յ x Յ 0.650 at 1730 K. [25] There are also two-phase regions between C11 b and C40, and between C40 and C54. However, we must avoid unnecessary structural change during oxidation since it may cause failure of the coating, so that the C40 single-phase material that has the largest composition range in Al content was selected as the candidate.…”

Section: A Determination Of Base Composition Of Al Reservoirmentioning

confidence: 99%

“…[32] Figure 2 indicates the dependence of the minimum thickness on x based on the assumption that the formed scale never spalls off. The C40 single-phase region at 1730 K [25] is also depicted in Figure 2, though the exact boundaries may be located on the slightly lower side at 1573 K. As can be seen from Figure 2, the thickness decreases with increasing x and there is the terminal of the C40 single-phase region around x ϭ 0.45.…”

Section: A Determination Of Base Composition Of Al Reservoirmentioning

confidence: 99%

“…[34] Thus, the predicted coating thickness of 175 m for Mo(Si 0.6 ,Al 0.4 ) 2 would be in the permissible range, and also in view of the possible oxide spallation, so x ϭ 0.4 was selected for the present study. growth at 1573 K for 10 4 h; the reported parabolic oxidation rate constants [32] were used in the calculation.…”

Section: A Determination Of Base Composition Of Al Reservoirmentioning

confidence: 99%

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Development of Mo(Si,Al)2-base oxidation-resistant coating on Nb-base structural materials

Tabaru

Kim

Shobu

et al. 2005

Metall Mater Trans A

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base oxidation-resistant coatings for Nb-base structural materials have been studied. The coating is composed of a Mo(Si,Al) 2 -base Al reservoir and Al 2 O 3 interlayer to suppress interface reactions between the Al reservoir and the substrate. To develop a suitable Al-reservoir material, some Mo(Si 0.6 ,Al 0.4 ) 2 -HfB 2 composites were prepared. Their oxidation resistance and coefficients of thermal expansion were investigated, in addition to their chemical reactivity with the Nb substrate at high temperatures. As a result, Mo(Si 0.6 ,Al 0.4 ) 2 -20 vol pct HfB 2 was selected as one of the satisfactory Al reservoirs. The introduction of a stable Al 2 O 3 interlayer was attempted using a novel powder metallurgical process to overlay the Nb substrates with the Al reservoir, where the Nb substrates were subjected to a slight surface oxidation prior to the coating process. The Nb specimens, which are thoroughly coated with the Al reservoir and Al 2 O 3 interlayer, can be successfully fabricated by this method. The coated Nb specimens are not damaged at all after prolonged exposure in flowing Ar-20 pct O 2 at 1673 K for 120 hours. Furthermore, the Al 2 O 3 interlayer is very effective and no reactions occur at the interface. Thus, this Mo(Si,Al) 2 -base oxidation-resistant coating is applicable to Nb. The utility of the coating system is also confirmed for a Nb SS /Nb 5 Si 3 composite.

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Section: A Determination Of Base Composition Of Al Reservoirmentioning

confidence: 99%

Section: A Determination Of Base Composition Of Al Reservoirmentioning

confidence: 99%

Section: A Determination Of Base Composition Of Al Reservoirmentioning

confidence: 99%

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Development of Mo(Si,Al)2-base oxidation-resistant coating on Nb-base structural materials

Tabaru

Kim

Shobu

et al. 2005

Metall Mater Trans A

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“…12 To overcome this problem, either the incorporation of ceramic phases to form MoSi 2 -based composites 4,16,17 or alloying treatment [18][19][20] has been proposed to improve the low-temperature oxidation resistance of MoSi 2 . Amongst different alloying elements used, Al was thought to be the most favorable candidate, 21 due to the fact that Al has stronger affinity to oxygen than Si. The formation of Al 2 O 3 only caused a minor volume expansion of 4.9% as compared to 85.6% for SiO 2 .…”

Section: Introductionmentioning

confidence: 99%

Oxidation resistance of Mo(Si_1−xAl_x)₂ nanocrystalline films and characterization of their oxide scales by electrochemical impedance spectroscopy

Munroe

et al. 2014

RSC Adv.

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To explore the influence of Al alloying on the oxidation resistance of MoSi 2 , four Mo(Si 1Àx Al x ) 2 nanocrystalline films, with differing Al contents, were fabricated on Ti-6A1-4V substrates by a doublecathode glow discharge technique and their cyclic oxidation behavior was characterized at 500 C in air.The oxidation kinetics of the four Mo(Si 1Àx Al x ) 2 films was found to obey a subparabolic behavior with respect to the overall exposure, and their oxidation resistance was improved by Al additions. On the other hand, the electrochemical behavior of the oxide scales developed on the four Mo(Si 1Àx Al x ) 2 nanocrystalline films in a 3.5 wt% NaCl solution was studied using electrochemical-impedance spectroscopy (EIS). The impedance data showed that with increasing oxidation time, the oxide scales transformed from a homogeneous and dense structure to a duplex structure consisting of a porous outer layer and a denser inner layer. The resistance of the oxide scales increased with increasing Al addition, implying an enhanced protective ability of the oxide scales by Al alloying in media containing chlorine ions. The findings represent a step forward in improving the surface integrity of alloy components used in the hot zones of jet engines.

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“…Aluminum was found to be one of the most effective alloying elements to improve the lowtemperature oxidation behavior of MoSi 2 [13][14][15][16][17][18][19][20][21]. The beneficial effect of Al on the oxidation behavior is believed to be due to the formation of a protective Al 2 O 3 layer [12-14, 19, 20, 22].…”

Section: Introductionmentioning

confidence: 99%

Effect of Al addition on the microstructure and low-temperature reactivity to oxygen of pre-formed MoSi2

et al. 2012

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The effect of aluminum addition on the structural and low-temperature oxidation behavior of commercially available MoSi 2 was investigated by means of X-ray diffraction and thermogravimetric analysis. MoSi 2 ? x Al compounds (with x = 0.0, 0.10, 0.20, 0.30, and 0.40) were mechanically processed for 6 h starting from a-MoSi 2 and Al powders. It is shown that Al can substitute Si atoms in pre-formed MoSi 2 leading to the formation of b-MoSi 2 (the high temperature phase). The unit cell volume of b-MoSi 2 increases linearly with the Al content. For x \ 0.20, a clear onset temperature for the oxidation of MoSi 2 is discernable at ca. 420°C, while it is barely noticeable for x C 0.20. The normalized mass gain decreases from *12 % m -2 to less than 2 % m -2 when the Al content varies from 0.0 to 0.2. For x C 0.20, the normalized mass gain stays constant at less than 2 % m -2 .

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Influences of Al content and secondary phase of Mo5(Si,Al)3 on the oxidation resistance of Al-rich Mo(Si,Al)2-base composites

Cited by 41 publications

References 26 publications

Development of Mo(Si,Al)2-base oxidation-resistant coating on Nb-base structural materials

Development of Mo(Si,Al)2-base oxidation-resistant coating on Nb-base structural materials

Oxidation resistance of Mo(Si_1−xAl_x)₂ nanocrystalline films and characterization of their oxide scales by electrochemical impedance spectroscopy

Effect of Al addition on the microstructure and low-temperature reactivity to oxygen of pre-formed MoSi2

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Influences of Al content and secondary phase of Mo5(Si,Al)3 on the oxidation resistance of Al-rich Mo(Si,Al)2-base composites

Cited by 41 publications

References 26 publications

Development of Mo(Si,Al)2-base oxidation-resistant coating on Nb-base structural materials

Development of Mo(Si,Al)2-base oxidation-resistant coating on Nb-base structural materials

Oxidation resistance of Mo(Si1−xAlx)2 nanocrystalline films and characterization of their oxide scales by electrochemical impedance spectroscopy

Effect of Al addition on the microstructure and low-temperature reactivity to oxygen of pre-formed MoSi2

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Oxidation resistance of Mo(Si_1−xAl_x)₂ nanocrystalline films and characterization of their oxide scales by electrochemical impedance spectroscopy