| 1. |
- Ingemarsson, Linda, 1972, et al.
(författare)
-
Oxidation behavior of a Mo (Si, Al)(2)-based composite at 300-1000 degrees C
- 2010
-
Ingår i: Intermetallics. - : Elsevier BV. - 0966-9795 .- 1879-0216. ; 18:4, s. 633-640
-
Tidskriftsartikel (refereegranskat)abstract
- The oxidation behavior of a Mo (Si,Al)(2)-based composite of Mo(Si,Al)(2), Al2O3 and Mo-5(Si,Al)(3) (Kanthal Super ER) in synthetic air was investigated. The samples were oxidized isothermally for up to 72 h at 300-1000 degrees C using a thermobalance. The microstructure was analyzed by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Auger Electron Spectroscopy (AES) depth profiling. Broad ion beam milling (BIB) was used to prepare cross-sections. Oxidation behavior depended strongly on the composition of the substrate which consisted of a Mo(Si,Al)(2) matrix and the minority phases Mo-5(Si,Al)(3) and Al2O3. At 300-500 degrees C the mass gains were small with parabolic kinetics, oxidation resulting in a mixture of oxides that reflects the substrate composition. At 600 and 700 degrees C the oxide scale is thin and protective and depleted in molybdenum, a mass loss occurring due to MoO3 vaporization. At 1000 degrees C a protective alpha-alumina scale forms.
|
|
| 2. |
|
|
| 3. |
- Ingemarsson, Linda, 1972, et al.
(författare)
-
Oxidation behavior at 300–1000C of a (Mo,W)Si2-based composite containing boride
- 2010
-
Ingår i: Intermetallics. - : Elsevier BV. - 0966-9795. ; 18:1, s. 77-86
-
Tidskriftsartikel (refereegranskat)abstract
- The oxidation behavior of a (Mo,W)Si2 composite with boride addition was examined at 300–1000C for24 h in dry O2. The oxidation kinetics was studied using a thermobalance, and the oxide scales wereanalyzed using a combination of electron microscopy (SEM/EDX, FIB, BIB) and XRD. Accelerated oxidationwas found to occur between 500C and 675C, with a peak mass gain at 625C. The rapid oxidation isattributed to the vaporization of molybdenum oxide that leaves a porous and poorly protective silicalayer behind. At higher temperature (700–1000C) a protective scale forms, consisting of a dense SiO2/B2O3 glass.
|
|
| 4. |
- Ingemarsson, Linda, 1972, et al.
(författare)
-
Oxidation behavior of a Mo(Si,Al)2 composite at 900–1600 C in dry air
- 2013
-
Ingår i: Journal of Materials Science. - : Springer Science and Business Media LLC. - 0022-2461 .- 1573-4803. ; 48:4, s. 1511-1523
-
Tidskriftsartikel (refereegranskat)abstract
- The oxidation of a Mo(Si,Al)2-based compositeis investigated in the temperature range 900–1600 C indry air. Exposure time was 72 h. Comparisons are madewith the oxidation behavior of a conventional MoSi2-basedmaterial. Cross-sections are examined with scanning electronmicroscopy and transmission electron microscopy; thephase composition is analyzed by X-ray diffraction andconvergent beam electron diffraction. The material forms acontinuous external a-alumina scale throughout the temperature range. Below the scale, there is a continuousMo5(Si,Al)3 layer that overlies Mo(Si,Al)2 in the bulk. TheMo(Si,Al)2 phase immediately beneath the Mo5(Si,Al)3layer is depleted in Al. No indications of MoO3 volatilization could be found for the Mo(Si,Al)2 material
|
|
| 5. |
- Ingemarsson, Linda, 1972, et al.
(författare)
-
Oxidation behaviour of a Mo(Si,Al)2 based composite at 1500 degrees C
- 2011
-
Ingår i: Intermetallics. - : Elsevier BV. - 0966-9795. ; 19:9, s. 1319-1329
-
Tidskriftsartikel (refereegranskat)abstract
- The oxidation of a Mo(Si,Al)(2) composite is investigated at 1500 degrees C in dry air using exposure times from 1 to 1000 h. Cross sections are examined with Scanning Electron Microscopy (SEM) and the phase composition is analyzed by X-ray diffraction (XRD). The material forms a continuous and protective alumina layer, the growth of the alumina layer following parabolic kinetics. Immediately below the scale Mo(Si,Al)(2) is replaced by a Mo(5)(Si,Al)(3) layer due to the flux of aluminum to the scale. The Al concentration in the Mo(Si,Al)(2) phase in the underlying substrate decreases from 27% before exposure to 16-17% after 1000 h. The continuous alumina layer becomes covered by a top layer consisting of alumina grains embedded in a viscous melt with approximate composition 7 Na(2)O-15 Al(2)O(3)-78 SiO(2). With time, sodium is volatilized from the melt and the top scale layer transforms to a mixture of alumina, mullite and silica melt.
|
|
| 6. |
|
|
| 7. |
- Ingemarsson, Linda, 1972
(författare)
-
Oxidation of MoSi2-based materials with the addition of W, B and Al
- 2009
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- MoSi2-based composites are intermetallic materials that combine metallic and ceramic properties. Because of their excellent oxidation resistance above 1000°C, they are commonly used in high temperature applications, such as furnace heating elements, where they can be used up to approximately 1800°C. However, there are some problems that limit a broader use of the material, such as accelerated oxidation/‘pesting’ at intermediate temperatures (400°C–700°C). A key issue is therefore improving the mechanical properties of this material and the pesting behaviour while maintaining the high temperature oxidation resistance. The aim of this work was to study the oxidation behaviour of the silica-forming (Mo,W)Si2-based composite with additions of boron and the alumina-forming Mo(Si,Al)2-based composite at temperatures between 300 and 1000°C (in dry oxygen/air). The initial oxidation of the Mo(Si,Al)2-based composite at high temperatures was also investigated. Oxidation kinetics were studied using thermogravimetric analysis (TGA), and the oxidized samples were analysed with a wide range of methods, including SEM/EDX, FIB/BIB, STEM/SEM, XRD and AES. The boron-reinforced (Mo,W)Si2 composite showed rapid oxidation in the intermediate temperature region (about 500–700°C), although pesting was not observed. The vaporization of MoO3 (and to some extent WO3) resulted in porous and poorly protective oxide scales. A dense and protective SiO2/B2O3 scale was established above 700°C. The presence of boron lowered the viscosity compared to a pure silica scale and is believed to be beneficial to the oxidation behaviour. The Mo(Si,Al)2-based composite showed excellent oxidation behaviour in the temperature regime investigated. No accelerated oxidation was observed, and the mass gains were low at all temperatures studied. At 300–700°C, the oxide consisted of a mixture of the oxides of Al, Si and Mo. At 600 and 700°C, the evaporation of MoO3 resulted in a molybdenum depletion of the oxide. At 1000°C, a protective alumina scale formed with a subjacent Mo5(Si,Al)3 region. The initial oxidation of the Mo(Si,Al)2-based composite at 1500 and 1450°C resulted in the formation of a dense and protective Al2O3 scale. The Al supply to the growing alumina scale was mainly provided by the Mo(Si,Al)2 phase in the substrate and resulted in the formation of a Mo5(Si,Al)3 region directly below the scale and an underlying region of Mo(Si1.4,Al0.6). Keywords: (Mo,W)Si2, Mo(Si,Al)2, accelerated oxidation, temperature dependence, protective oxide scales, SEM/EDX, XRD.
|
|
