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

Chattopadhyay, Kausik; Mitra, Rahul; Ray, K. K.

doi:10.1007/s11661-007-9398-9

Cited by 45 publications

(29 citation statements)

References 42 publications

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“…Comparison of the data given in Table 6 indicates that the oxidation resistance of the NbCrMo 0.5 Ta 0.5 TiZr alloy is much better than that of the Nb-Al, Nb-Si, Nb-Si-Al, and Nb-Si-Al-Ti alloys, as well as Nb-13Si-4Mo and Nb-19Si-5Mo alloys, and similar to that of the Nb-18Si-26Mo alloy. However, oxidation resistance of the developmental Nb-12Si-15Mo alloy [29] is slightly better than that of our alloy.…”

Section: Oxidation Kineticscontrasting

confidence: 60%

“…FA8650-10-5226. Nb-10Si 37 ---- [29] Nb-10.1Si 45 90 170 -- [28] Nb-17.3Al 23 43 65 -- [28] Nb-5Si-9Al 90 160 275 -- [28] Nb-7Si-9Al 69 145 275 -- [28] Nb-8Si-9Al-10Ti ---182 338 [28] Nb-10Si-9Al-10Ti ---95 291 [28] Nb-6Si-11Al-15Ti ---51 167 [28] Nb-8Si-11Al-15Ti ---51 153 [28] Nb-19Si-5Mo 26 53 106 -- [29] Nb-18Si-26Mo 9.7 13.8 19.5 45 - [29] Nb-13Si-4Mo 48 105 166 -- [29] Nb-12Si-15Mo …”

Section: Discussionunclassified

“…Without protective coating, oxidation of these alloys occurs very rapidly, with considerable weight gain, which generally exceeds 0.04 mg/cm 2 /s (150 mg/ cm 2 /h), followed by alloy embrittlement and disintegration. Several developmental Nb alloys with improved oxidation resistance, containing Ti, Si, Al, and some other elements, have recently been reported [27][28][29]. Unfortunately, these developmental alloys contain high volume fractions of silicides and aluminides and are brittle at temperatures less than *1000 K. The results of isothermal oxidation at 1273 K of these developmental alloys are given in Table 6.…”

Section: Oxidation Kineticsmentioning

confidence: 99%

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Oxidation behavior of a refractory NbCrMo0.5Ta0.5TiZr alloy

et al. 2012

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Isothermal oxidation behavior of a refractory high-entropy NbCrMo 0.5 Ta 0.5 TiZr alloy was studied during heating at 1273 K for 100 h in flowing air. Continuous weight gain occurred during oxidation, and the time dependence of the weight gain per unit surface area was described by a parabolic dependence with the time exponent n = 0.6. X-ray diffraction and scanning electron microscopy accompanied by energy-dispersive X-ray spectroscopy showed that the continuous oxide scale was made of complex oxides and only local (on the submicron levels) redistribution of the alloying elements occurred during oxidation. The alloy has a better combination of mechanical properties and oxidation resistance than commercial Nb alloys and earlier reported developmental NbSi-Al-Ti and Nb-Si-Mo alloys.

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Section: Oxidation Kineticscontrasting

confidence: 60%

Section: Discussionunclassified

Section: Oxidation Kineticsmentioning

confidence: 99%

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Oxidation behavior of a refractory NbCrMo0.5Ta0.5TiZr alloy

et al. 2012

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“…Nb-Si-Mo alloys were examined by Chattopadhyay et al [15] The authors determined that the oxidation behavior was controlled at intermediate temperatures by the hypo-, hyper-eutectic character of the alloy as a result of the accelerated oxidation of large volume fractions of (Nb,Mo) 5 lowers porosity and reduces oxygen diffusion and increases the activity of silicon leading to the development of a layer of SiO 2 . A characteristic multilayer oxide scale is developed on samples that consist of dispersed Nb 2 O 5 particles in a borosilicate glass matrix when boron is added.…”

Section: Introductionmentioning

confidence: 99%

Oxidation Behavior of Nb-20Mo-15Si-25Cr and Nb-20Mo-15Si-25Cr-5B Alloys

Portillio

Varma

2011

Metall Mater Trans A

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Nb-20Mo-15Si-25Cr (25Cr alloy) and Nb-20Mo-15Si-25Cr-5B (25Cr/5B alloy) alloys have been subjected to oxidation in air for 24 hours from 973 K to 1673 K (700°C to 1400°C). Even though B additions do not improve oxidation resistance at temperatures higher than 1473 K (1200°C), the lower temperature oxidation resistance is superior with B by influencing the microstructure. Porous oxide scale development at lower temperatures has been attributed to the dominant growth of Nb 2 O 5 and the vaporization of MoO 3 . An intermediate oxidation layer is developed between the scale and the metal for the 25Cr/5B alloy at temperatures above 1173 K (900°C). Scale densification at elevated temperatures results in higher stress development as a result of the mismatch of coefficients of thermal expansion, ultimately resulting in oxide spallation.

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“…It was recently found that the addition of Mo increases the oxidation resistance at high temperature. [2] So, it is important to study the interdiffusion in the Nb-Mo system, which will be helpful in designing the alloy for the application. There are some studies available [3][4][5] in the literature; however, significant differences were found in different studies.…”

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confidence: 99%

Diffusion Parameters in the Nb-Mo System: Revisited

Prasad

Paul

2009

Metall Mater Trans A

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The variation of the interdiffusion coefficient with the change in composition in the Nb-Mo system is determined in the temperature range of 1800°C to 1900°C. It was found that the activation energy has a minimum at around 45 at. pct Nb. The values of the pre-exponential factor and the activation energy for diffusion are compared with the data available in the literature. Further, the impurity diffusion coefficients of Nb in Mo and Mo in Nb are calculated.Refractory metals draw special attention in hightemperature applications. The elements Mo, W, Ta, Re, and Nb are used in Ni-based superalloys to improve creep resistance for the application in air and land-based gas turbine applications. [1] Recently, there has been enormous effort to find a material system that can replace Ni-based superalloys operating at its limit. A further increase in operating temperature is difficult, because it seems now that all of the possible manufacturing methods or alloying additions have been explored. So there is a search for a completely new material system, which can operate at much higher temperature to increase the efficiency as well as decrease the emission of unwanted gases. In this regard, Nbbased silicides are considered as one of the best potential systems; they have an even higher strength-to-density ratio [1] compared to Ni-based superalloys. Room-temperature fracture toughness has reached the minimum required level with the help of alloying additions. [1] Further research is being carried out to improve the oxidation resistance. It was recently found that the addition of Mo increases the oxidation resistance at high temperature. [2] So, it is important to study the interdiffusion in the Nb-Mo system, which will be helpful in designing the alloy for the application. There are some studies available [3][4][5] in the literature; however, significant differences were found in different studies. With the renewed interest in this system, it is necessary to revisit the system to re-examine the data available in the literature.The diffusion couple technique is used to determine the interdiffusion coefficient at three different temperatures of 1800°C, 1875°C, and 1900°C in a vacuum level of~10 -6 mbar. Interdiffusion studies were conducted at a lower temperature range also; however, the interaction zone was found to be very small and was excluded from the present report. A very thin interdiffusion zone introduces significant error in the calculation because of the introduction of the inaccuracy in determining the composition gradient. For example, Vergasova et al. reported the interdiffusion data at 1100°C, [6] where the interdiffusion zone is actually less than 1 lm. It is almost impossible to determine the variation of interdiffusion coefficients with composition following conventional techniques, when the interdiffusion zone is so small. In the temperature range of our interest, the interaction zone was found to vary from 65 to 138 lm. The Nb with purity of 99.8 wt pct and Mo with purity of 99.95 wt pct supplied by Alfa Aesa...

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

Cited by 45 publications

References 42 publications

Oxidation behavior of a refractory NbCrMo0.5Ta0.5TiZr alloy

Oxidation behavior of a refractory NbCrMo0.5Ta0.5TiZr alloy

Oxidation Behavior of Nb-20Mo-15Si-25Cr and Nb-20Mo-15Si-25Cr-5B Alloys

Diffusion Parameters in the Nb-Mo System: Revisited

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