| 1. |
- Esmaily, Mohsen, 1987, et al.
(författare)
-
Corrosion behavior of alloy AM50 in semi-solid cast and high pressure die cast states in cyclic conditions
- 2015
-
Ingår i: Corrosion. - : Association for Materials Protection and Performance (AMPP). - 0010-9312 .- 1938-159X. ; 71:6, s. 737-748
-
Tidskriftsartikel (refereegranskat)abstract
- The atmospheric corrosion behavior of the Mg-Al alloy AM50 produced by high pressure die casting (HPDC) and a semi-solid metal (SSM) technique was studied under alternating wet-dry conditions for up to 672 hours. The alloy AM50 in the SSC state was fabricated using rheocasting (RC) technique in which the slurry was prepared by the newly developed RheoMetal process. To simulate the real-world atmospheric environment, the exposure program included a 6 hour wet phase (including rain with 0.5 % NaCl), a 2.5 hours transition phase followed by a 15.5 hours dry phase at 50°C and 70% relative humidity (RH). The results showed that the RC alloy was substantially less prone to corrosion than the HPDC material in the cyclic wet/dry atmosphere. Based on the gravimetric results and microstructural characterization studies, this was attributed to a lower fraction of porosity and to the barrier role of β phase particles in the RC.
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- Hansson, Kristina, 1971, et al.
(författare)
-
On the Mechanism of MoSi2 Pesting in the Temperature Range 400–500°C
- 2000
-
Ingår i: Ceramic Engineering and Science Proceedings. - 0196-6219 .- 1940-6339. ; 21:4, s. 469-476
-
Tidskriftsartikel (refereegranskat)abstract
- The oxidation of a MoSi2 composite was studied in the temperature range 400–500°C. The peak pesting temperature was identified and the oxidation kinetics was observed up to a holding time of 4000 hours. The reaction kinetics was tracked using thermogravimetric analysis :IS well iis oxide thickness nieasurenients. A detailed analysis of the morphology and composition of the oxide was performed using SEM and EDX. The peak pesting temperature was found to be 470°C. The reaction kinetics in static air could be described with two consecutive parabolic oxidation curves, one up to 500 hours and another between 500–4000 hours. With a higher water vapor coiitent the kinetics showed linear behwior. MoO3 evaporation took place during the entire duration of the oxidation. The oxide appeared to grow by inward diffusion of oxygen to the oxidehulk interface.
|
|
| 5. |
- Hansson, Kristina, 1971, et al.
(författare)
-
Oxidation behaviour of a MoSi2-based composite in different atmospheres in the low temperature range (400–550 °C)
- 2004
-
Ingår i: Journal of the European Ceramic Society. - : Elsevier BV. - 1873-619X .- 0955-2219. ; 24:13, s. 3559-3573
-
Tidskriftsartikel (refereegranskat)abstract
- The oxidation characteristics of a MoSi2-based composite within the temperature range of 400–550 °C were investigated. The effects of temperature and water vapour on oxidation were examined. The oxidation kinetics were studied using a thermobalance, while the morphology and composition of the oxides were examined using XRD, ESEM/EDX, and SEM/EDX.The peak oxidation rates in dry O2 and View the MathML source were found to occur at temperatures of approximately 510 and 470 °C, respectively. Within the temperature range of accelerated oxidation (400–500 °C), the oxidation rate in View the MathML source was substantially higher than that in dry O2. At higher temperatures, the oxidation rate decreased, and the magnitude of the decrease was steeper and occurred at a lower temperature for View the MathML source (510 °C) than for O2 (550 °C). Furthermore, the rate of depletion of molybdenum (Mo) from the oxide scales during oxidation increased with increasing temperature and water vapour content. It appears that Mo loss is a key process influencing the protective properties of the oxide layer on the MoSi2 composite. A potential mechanism for the different oxidation behaviours in O2 and View the MathML source is proposed.
|
|
| 6. |
- Hansson, Kristina, 1971, et al.
(författare)
-
The beneficial effect of water vapour on the oxidation at 600 and 700 °C of a MoSi2-based composite
- 2005
-
Ingår i: JOURNAL OF THE EUROPEAN CERAMIC SOCIETY. ; 25:1, s. 1-11
-
Tidskriftsartikel (refereegranskat)abstract
- The oxidation characteristics of a MoSi2-based composite in O2 and O2+10% H2O at 600 and 700 °C were investigated. The effects of temperature and water vapour on oxidation were examined. The oxidation kinetics were studied using a thermobalance and furnace exposure, while the morphologies and compositions of the oxides were examined using XRD, ESEM/EDX, and SEM/EDX. We propose that oxidation proceeds by the initial formation of MoO3 crystals and amorphous SiO2 on the surface. The MoO3 is then evaporated; as volatile (MoO3)3 species in O2 and additional MoO2(OH)2 species in O2+10% H2O, which results in a porous, Mo-depleted oxide. However, the pores in the Mo-depleted SiO2 scale heal, and a protective crystalline scale is established eventually. The vapour pressures of the abovementioned volatile species increase with temperature and/or water vapour content in the atmosphere, which leads to accelerated Mo depletion from the oxide scale. A shorter time elapses before the oxide scale is transformed into the relatively Mo-free protective SiO2 scale, which results in less oxide being formed. Thus, the formed scale becomes thinner in O2+10% H2O than in O2. Thereby the Mo removal is beneficial when water vapour is added to the exposure atmosphere.
|
|
| 7. |
- Hansson, Kristina, 1971, et al.
(författare)
-
The influence of water vapor on the oxidation of MoSi2 at 450 °C
- 2001
-
Ingår i: Materials Science Forum. - 1662-9752 .- 0255-5476. ; 369-372, s. 419-426
-
Tidskriftsartikel (refereegranskat)abstract
- The oxidation of a MoSi2 composite was studied in dry air, oxygen and oxygensaturated with 10% water vapour at 450°C. The kinetics were investigated using TGA as well as oxide thickness measurements. Detailed analyses were performed on the morphology and composition of the oxide using XRD, ESEM, SEM, and EDX. It is shown that the oxidation rate increases drastically in the presence of water vapour, and the growth of Mo03 crystals on the oxide surface increases considerably. The different regions in the oxide cross-section are Mo-depleted compared with the corresponding regions in the bulk when oxidised in oxygen saturated with 10% water vapour. However, the samples oxidised in dry oxygen only shows Mo-depletion in some outer parts of the oxide. Accelerated growth of the MoSi2-oxide layer during exposure in 02+10%H20 compared to that in 02 can be related to the fact that more volatile Mo-species form in the presence of water vapour, resulting in a substantial loss of Mo03 from the inner part of the oxide. The voids left behind are not healed by the silica at this low temperature, which leaves the oxide with an open structure. As a result, the oxidation rate increases.
|
|
| 8. |
- Hellström, Kristina M, 1971, et al.
(författare)
-
Oxidation behaviour of a (Mo, W)Si2-based composite in dry and wet oxygen atmospheres in the temperature range 350–950◦C
- 2009
-
Ingår i: Journal of the European Ceramic Society. - : Elsevier BV. - 1873-619X .- 0955-2219. ; 29:10, s. 2105-2118
-
Tidskriftsartikel (refereegranskat)abstract
- The oxidation of a (Mo, W)Si2-based composite was investigated in the temperature range (350–950 °C). The influence of temperature and water vapour on the oxidation was examined. The kinetics was studied using a thermobalance whereas the morphology and composition of the oxides were examined using X-ray diffractometer (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and energy dispersive X-ray (EDX). Focused ion beam (FIB) milling was performed on some of the oxide scales which allowed us to look at a non-mechanically disturbed scale/oxide in cross-section. Rapid oxidation was found to occur in the 550–750 °C temperature range. The mass gains were significantly larger in O2 than in O2 + 10%H2O. The different mass changes in the two exposure atmospheres were attributed to the higher vapour pressure of the volatile MoO2(OH)2 and WO2(OH)2 species in O2 + 10%H2O than that of (MoO3)3 and (WO3)3 in dry O2. The peak mass gain was found to occur at a temperature of about 750 °C in O2 and 650 °C in O2 + 10%H2O. At temperatures above 850 °C, especially when water vapour is present, the removal of Mo and W from the oxide scales is rapid enough to allow partial healing of the silica, causing the oxidation rate to drop. At 950 °C in O2 + 10%H2O, a protective SiO2 scale could be re-established quickly and maintained, causing the oxidation to essentially cease.
|
|
| 9. |
- 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.
|
|
| 10. |
|
|
