Oxidation mechanisms of niobium, tantalum, molybdenum and tungsten

Kubaschewski, O.; Hopkins, B. E.

doi:10.1016/0022-5088(60)90012-6

Cited by 107 publications

(83 citation statements)

References 23 publications

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“…The results of this study agree well with that of a few previous publications, [16,[32][33] which have suggested that alloying of Nb with Mo is beneficial for oxidation resistance. MoO 2 has the free energy of formation closest to that of Nb 2 O 5 , [37] among the oxides of Mo.…”

Section: Oxidation Mechanismssupporting

confidence: 94%

“…The molar volume of monoclinic b-Nb 2 O 5 is 58.3 cm 3 , while that of Nb is 10.9 cm 3 , [16] suggesting that volume expansion on oxidation of Nb is large. Such a large volume expansion naturally causes high biaxial residual stress at the metal-oxide interface, leading to spallation.…”

Section: Introductionmentioning

confidence: 98%

“…The SiO 2 layer at the metal-oxide interface is shown with a pair of arrows.alloys, reports the presence of Nb 2 O 5 in the oxide scales [16][17][18]22,24,[30][31][32][33][34]. Thus the formation of Nb 2 O 5 in the oxide scale is kinetically driven.…”

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confidence: 97%

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Nonisothermal and Isothermal Oxidation Behavior of Nb-Si-Mo Alloys

Chattopadhyay

Mitra

Ray

2008

Metall Mater Trans A

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The nonisothermal and isothermal oxidation behavior of arc-melted, hypereutectic ternary alloys have been investigated vis-a`-vis that of Nb and Nb-10Si alloy. The nonisothermal studies carried out using simultaneous thermogravimetric and differential thermal analysis in the temperature range of 50°C to 1300°C using heating rates of 5°C, 15°C/min, 25°C/min, and 40°C/min have shown oxidation initiation at lower temperatures for slower heating rates and higher Mo content. Isothermal oxidation experiments have been carried out in dry air at 800°C, 1000°C, and 1150°C for 24 hours and the kinetics have been examined by the power-law equation. The studies show that the ternary Nb-Si-Mo alloys undergo less mass gain compared to the Nb and the Nb-10Si alloy. The hypo-or hypereutectic character of the alloys controls the oxidation behavior at 800°C, while the effect of Mo content is predominant at temperatures of 1000°C to 1150°C. X-ray diffraction and scanning electron microscopy (SEM) accompanied by energy dispersive X-ray analysis have shown that the oxide scales of all the alloys are made of Nb 2 O 5 and SiO 2 . The beneficial effect of alloying with Mo is attributed to the improved sinterability of the oxide scale and increase in the activity of Si, which assists in the formation of a stable and continuous layer of SiO 2 at the alloy-oxide interface.

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Section: Oxidation Mechanismssupporting

confidence: 94%

Section: Introductionmentioning

confidence: 98%

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Nonisothermal and Isothermal Oxidation Behavior of Nb-Si-Mo Alloys

Chattopadhyay

Mitra

Ray

2008

Metall Mater Trans A

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“…Niobium, the major coating element, generally oxidizes very fast and nonprotective scale composed of NbO, NbO 2 or Nb 2 O 5 can be formed at temperatures as low as 400 o C [14]. The above facts will adversely affect the oxidation property.…”

Section: Discussionmentioning

confidence: 98%

High temperature sulfidation and oxidation of sputter-deposited Nb−Al−Si coatings

Lee

2001

Met. Mater. Int.

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The sulfidation and oxidation behavior of amorphous 58Nb-38Al-4Si(at.%) coating sputter-deposited with d.c. magnetron sputtering was studied between 700 and 900 o C under 0.1 atm of pure S 2 (g) and 1 atm of air, respectively. The coating approximately followed the parabolic sulfidation and oxidation rate law, and displayed superior resistance to sulfidation and oxidation. The coating sulfidized to Al 2 S 3 and NbS 2 which protected the substrate. The coating oxidized to TiO 2 , AlNbO 4 and κ-Al 2 O 3 which acted as an oxidation barrier. The mechanisms of sulfidation and oxidation of the prepared coating are discussed.

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“…Additionally, the oxidation resistance enhancement provided by the presence of niobium in the coatings, through the development of oxide scales such NbO and Nb 2 O 5 is under discussion. However, some authors have suggested that if these scales present low porosity and remain intact at high temperatures (do not develop cracks or porosity) [25][26][27][28][29] their oxidation resistance capability can be improved. Therefore a secondary objective was to analyse the effect of Nb concentration on the oxidation resistance of the CrN/NbN multilayer coatings.…”

Section: Introductionmentioning

confidence: 99%