Oxidation of Some Intermetallic Compounds and Intermetallic Matrix Composites

Jackson, M. R.; Rowe, R.G.; Skelly, D. W.

doi:10.1557/proc-364-1339

Cited by 19 publications

(15 citation statements)

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“…In addition, Nb 5 Si 3 undergoes accelerated pest disintegration in the temperature range of 700°C to 1000°C, forming Nb 2 O 5 . [17] Complete disintegration of the Nb 5 Si 3 has been observed on exposure at 1000°C for 1 to 3 hours. The susceptibility of pest disintegration of Nb-silicides is commonly attributed to the mismatch in the coefficient of thermal expansion (CTE) of the oxidation products, along with the volume expansion accompanying the oxide growth.…”

Section: Introductionmentioning

confidence: 94%

“…The higher oxidation rate of the hypereutectic alloys at 800°C could be attributed to the tendency of the (Nb,Mo) 5 Si 3 phase to undergo accelerated oxidation in the temperature range of 700°C to 1000°C, as reported previously. [17] In addition, the alloys A and B with a significantly larger volume fraction of the eutectic also have a high area fraction of the Nb ss -(Nb,Mo) 5 Si 3 interfaces, which probably provide short circuit paths for diffusion of oxygen. In an earlier investigation on the oxidation behavior of the multicomponent Nb-Si-based alloys, Menon et al [22] have shown that the grain boundaries and interfaces enhance the rate of diffusion of oxygen.…”

Section: Oxidation Mechanismsmentioning

confidence: 99%

“…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: 99%

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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: Introductionmentioning

confidence: 94%

Section: Oxidation Mechanismsmentioning

confidence: 99%

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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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“…[16] Recent efforts have focused mostly on materials that contain substantial amounts of niobium silicides and Laves phases. [20][21][22][23][24][25][26][27][28][29][30][31][32] These new systems include Nb-Si, Nb-Ti-Si, Nb-Ti-Al-Si, Nb-Ti-Cr-Si, and, among others, Nb-Ti-Hf-Cr-Al-Si. In these Nb-based alloys, Ti and Hf additions are intended for improvement in fracture [24,33,34] and oxidation resistance.…”

Section: Introductionmentioning

confidence: 99%

Cyclic oxidation response of multiphase niobium-based alloys

Chan

2004

Metall Mater Trans A

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Cyclic oxidation tests were performed on multiphase Nb-based alloys containing silicide, Laves, and Nb solid solution phases. In particular, the oxidation resistance of six alloys with various compositions (Nb, Ti, Hf, Cr, Ge, and Si) and microstructures was characterized by thermal cycling from ambient temperature to a peak temperature that ranges from 900°C to 1400°C. Weight change data were obtained and the corresponding spalled oxides were collected and identified by X-ray diffraction. The results indicated that Nb-based alloys formed a mixture of CrNbO 4 , Nb 2 O 5 , and Nb 2 O 5 и TiO 2 , with possibly small amounts of SiO 2 or GeO 2 . The oxidation resistance was improved when CrNbO 4 formed instead of Nb 2 O 5 and Nb 2 O 5 и TiO 2 . These results were used to assess the influence of microstructure and composition on the oxidation resistance of multiphase Nb-based alloys.

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“…There has been particular emphasis on Ti and Hf additions to Nb-Si based composites. The oxidation resistance of these composites can be improved by partial substitution of Ti for Nb (Subramanian et al, 1996;Jackson et al, 1995). Hf is added because it is also a strong solid solution strengthener of the (Nb).…”

Section: Microstructure and Phase Stabilitymentioning

confidence: 99%