scholarly journals Effect of Total Pressure and Furnace Tube Material on the Oxidation of T22 in Humidified Air

2021 ◽  
Author(s):  
Clara Schlereth ◽  
Mathias C. Galetz
Keyword(s):  
Cross Sections ◽  
Base Alloy ◽  
Gas Composition ◽  
Oxide Scales ◽  
Tube Material ◽  
System Pressure ◽  
Furnace Tube ◽  
Adsorption Rates ◽  
Humidified Air ◽  
Micro Analysis

AbstractOxidation of the Fe-base alloy T22 in humid air at 500 °C was investigated. The samples were exposed for up to 1000 h at 1 bar and 20 bar. The influence of three furnace tube materials, alumina, ET45 and quartz glass, on the oxide scale morphology was investigated. Samples and their cross sections were examined using optical microscopy, scanning electron microscopy, electron probe micro analysis and Raman spectroscopy. Multilayered oxide scales consisting of hematite, magnetite and Fe–Cr spinel were found on all samples. However, the composition and morphology of the oxide scales depend on the furnace tube material and on the system pressure. The system pressure is assumed to change the reaction equilibria and adsorption rates. The tube material changed the initial gas composition by formation of volatile Cr species. This volatilization rate increased at higher system pressures.

Oxidation of Metallic Materials in Simulated CO2/H2O-Rich Service Environments Relevant to an Oxyfuel Plant

2011 ◽  
Vol 696 ◽  
pp. 194-199 ◽  
Author(s):  
W.Joe Quadakkers ◽  
T. Olszewski ◽  
J. Piron-Abellan ◽  
Vladimir Shemet ◽  
Lorenz Singheiser
Keyword(s):  
Water Vapour ◽  
Base Alloy ◽  
Gas Mixtures ◽  
Oxidation Behaviour ◽  
Oxide Scales ◽  
Martensitic Steels ◽  
Air Oxidation ◽  
Oxidation Rates ◽  
Service Environments ◽  
Nickel Base

In the present study the oxidation behaviour of a number of candidate alloys for heat exchanging components was investigated in model gas mixtures containing high amounts of CO2 and/or water vapour in the temperature range 550-700°C up to exposure times of 1000 h. During exposure in Ar/CO2 and Ar/CO2/H2O base gas mixtures at 550-650°C the oxidation rates and scale compositions of martensitic 9-12%Cr steels were similar to those previously observed in steam environments. Thin and protective Cr-rich oxide scales which are commonly found during air oxidation was observed locally on the specimens surfaces after oxidation in Ar-(1-3%)O2-CO2. The tendency for protective chromia base scale formation increased when 3% oxygen was added, especially for the 12%Cr steel. When iron base oxide scales were formed on the metal surface, the martensitic steels tended to exhibit carburisation whereby the extent was reduced by increasing the water vapour and oxygen contents. All three studied austenitic alloys exhibited very slow scale growth rates at 550°C, however, at and above 600°C the steels with lower Cr content started to form two-layered iron rich surface oxide scales whereby the outer oxide was prone to spallation upon thermal cycling. The high-Cr austenitic steel 310N and the nickel base alloy 617 formed very thin, Cr-rich oxide scales at all used test temperatures and atmospheres. For those two materials the oxidation behaviour in gases containing water vapour in combination with intentionally added oxygen was affected by formation of volatile chromium oxyhydroxide.

scholarly journals Numerical Analysis of Microchannels Designed for Heat Sinks

2021 ◽  
Author(s):  
Matthew McCormack ◽  
Fengzhou Fang ◽  
Jufan Zhang
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Cross Sections ◽  
High Performance ◽  
Three Dimensional ◽  
Heat Fluxes ◽  
Dean Flow ◽  
System Pressure ◽  
Spatial Frequencies ◽  
Geometric Variation

AbstractConjugate heat transfer is numerically investigated using a three-dimensional computational fluid dynamics approach in various microchannel geometries to identify a high-performance cooling method for piezoelectric ceramic stacks and spindle units in high-precision machines. Straight microchannels with rectangular cross sections are first considered, showing the performance limitations of decreasing the size of the microchannels, so other solutions are needed for high applied heat fluxes. Next, many microchannel designs, focusing on streamwise geometric variation, are compared to straight channels to assess their performances. Sinusoidally varying channels produce the highest heat transfer rates of those studied. Thus, their optimization is considered at a channel width and height of 35 and 100 μm, respectively. Heat transfer increases as the amplitude and spatial frequencies of the channels increase due to increased interfacial surface area and enhanced Dean flow. The highest performance efficiencies are observed at intermediate levels of amplitude and frequency, with efficiency decreasing as these geometric parameters are increased further at the onset of flow separation. The sinusoidal channel geometries are then optimized with respect to minimizing the system’s pressure drop for all applied heat fluxes between 5690 and 6510 kW/m2. Doing so created an optimal geometry curve and showed that all geometries in this region had amplitudes close to 40 μm. Therefore, imposing a fixed heat flux requirement for a case study of cooling piezoelectric ceramics, the optimized sinusoidal geometry decreases the system pressure drop by 79% relative to a straight channel while maintaining a larger minimum feature size.

Effects of Si Content on the Oxidation Behavior of Fe–Si Alloys in Air

2011 ◽  
Vol 696 ◽  
pp. 126-131 ◽  
Author(s):  
Takumi Nishimoto ◽  
Kazuhiko Honda ◽  
Yasumitsu Kondo ◽  
Kenichi Uemura
Keyword(s):  
Oxide Scale ◽  
Cross Sections ◽  
Oxidation Kinetics ◽  
Oxidation Behavior ◽  
Elemental Distribution ◽  
Oxide Scales ◽  
Scale Thickness ◽  
Internal Oxidation Zone ◽  
Diffusion Controlled ◽  
Si Content

The oxidation behavior of Fe–Si alloys at 1073K in air was investigated. The oxidation kinetics described by the parabolic rate law of diffusion controlled oxidation and the oxidation rate decrease with the increasing Si content. Fe-Si alloys were oxidized for different times at 1073K to obtain the same scale thickness of approximately 30μm. Observations of scale cross-sections indicated the structure of oxide scale and elemental distribution in oxide scales strongly depends on Si content. The oxide scale on Fe-Si alloys with low Si content consisted of three layers with an outer Fe2O3, an intermediate Fe3O4 and an inner FeO and some voids were formed in Fe3O4 and FeO layers. The Si-rich oxide layer was formed at the scale/alloy interface of Fe-Si alloys with high Si content. Furthermore, the amount of internal oxidation zone increased with the increasing Si content. Observations of scale cross-sections indicated that the structure of oxide scale and elemental distribution in oxide scale strongly depend on Si content.

Effect of Pt Content on TGO Growth in EB-PVD TBC Systems with Niptal Bondcoats

2013 ◽  
Vol 690-693 ◽  
pp. 2051-2054
Author(s):  
Peng Song ◽  
Jian Sheng Lu
Keyword(s):  
Growth Rate ◽  
Cross Sections ◽  
Oxidation Behavior ◽  
Base Alloy ◽  
Aluminide Coating ◽  
Initial Oxidation ◽  
Oxide Spallation ◽  
Tbc Lifetime ◽  
Tbc Systems ◽  
Tgo Growth

The oxidation behavior of Pt modified aluminide coating on the CMSX-4 Ni-base alloy plays major role to the EB-PVD TBC failure. The thermally growth oxide (TGO) is one of the most important factors to affect TBC lifetime. Two different Pt-content NiPtAl coatings in EB-PVD TBC systems were studied at 1100°C in air. The results indicated that cross-sections of oxide layer on the NiPtAl coatings within TBC in air were similar for the both bondcoats. The cracks could be found on the TBC/TGO/BC interfaces for the two bondcoats. The TGO morphologies of the low and high-Pt bondcoats on the side without TBC showed great different due to small PtAl particles size within high-Pt bondcoats. The irregular alumina on the both bondcoats was also showed on the sides with TBC compared to ones without TBC due to absence of the TBC. The TGO growth on the high-Pt bondcoats was faster than the low-Pt coatings during initial oxidation time. With the time increasing, the high-Pt content could suppress the TGO growth rate. Thinner TGO thickness could be obeserved on the both NiPtAl coatings due to the stress in TGO accumulation and oxide spallation.

Measurement of collisional ionization cross-sections for metal atoms in flames

1972 ◽  
Vol 327 (1570) ◽  
pp. 345-366 ◽  
Keyword(s):  
Cross Sections ◽  
Ionization Rate ◽  
Elastic Collision ◽  
Gas Composition ◽  
Ionization Cross ◽  
Metal Atoms ◽  
Electrostatic Probe ◽  
Ionization Cross Sections ◽  
Collisional Ionization ◽  
Pressure Hydrogen

The rates of collisional ionization of gaseous metal atoms, M, in the temperature range 2000 to 2800 K have been measured by optical and electrostatic probe studies in over 100 fuel-rich, atmospheric pressure hydrogen + oxygen flames diluted with each of the gases argon, nitrogen, carbon monoxide and carbon dioxide. Individual cross-sections for the process M + X j → M + + e - + X j , with X j = Ar, H 2 , N 2 , CO, CO 2 and H 2 O, and M = Li, Na, K, Rb, Cs and Tl, have been determined from a detailed analysis of the dependence of the collisional ionization rate constants on burned gas composition. They lie between 10 and 145 nm2 and are given in table 4. They show no correlation with the corresponding optical quenching cross-sections for the first excited electronic states of M. The implications of these cross-sections are discussed with regard to both their large overall magnitude and their dependence on the nature of M and X j . Elastic collision, translational de-excitation of X j contributions appear to be at least as important as processes involving rotational or vibrational de-excitation of X j .

High-temperature oxidation behavior of arc ion plated NiCoCrAlYSiB coatings on cobalt-based superalloy

2006 ◽  
Vol 21 (3) ◽  
pp. 737-746 ◽  
Author(s):  
Y.J. Tang ◽  
Q.M. Wang ◽  
F.H. Yuan ◽  
J. Gong ◽  
C. Sun
Keyword(s):  
Cross Sections ◽  
High Temperature Oxidation ◽  
Oxidation Behavior ◽  
Alloy Element ◽  
Oxide Scales ◽  
Protective Oxide ◽  
Temperature Oxidation ◽  
Ion Plating ◽  
Aluminide Coatings ◽  
High Temperature Oxidation Behavior

NiCoCrAlYSiB coatings were deposited on the Co-based superalloy K40 by arc ion plating (AIP). The oxidation behavior of the bare alloy and of the coated specimens was tested in static air for 200 h at 1000 °C and 100 h at 1050 °C. The results showed that the oxidation rate of the system was greatly reduced by the addition of the NiCoCrAlYSiB coatings. Thin and adherent α–Al2O3 scales that formed on the coated specimens protected the substrates from further oxidation attack while non-protective oxide scales, mainly of Cr2O3 and CoCr2O4, appeared on bare K40 alloy. Element profiles on metallographic cross sections indicated that apparent interdiffusion occurred between the coatings and the substrates. The interdiffusion behavior and the resulting microstructure were investigated. As compared to aluminide coatings, NiCoCrAlYSiB coatings have less influence on the substrate microstructure.

Effect of Mg Content on the Precipitation in Al-Mg-Ge Alloys

2007 ◽  
Vol 561-565 ◽  
pp. 2049-2052 ◽  
Author(s):  
Kenji Matsuda ◽  
Teruyoshi Munekata ◽  
Susumu Ikeno
Keyword(s):  
Cross Sections ◽  
Base Alloy ◽  
Lattice Parameter ◽  
Chemical Compositions ◽  
Crystal Lattices ◽  
Β Phase ◽  
Selected Area Electron Diffraction ◽  
Transmission Electron ◽  
The Matrix ◽  
Mg Content

Rod-shaped precipitates in Al -1.1 mass% Mg2Ge (balanced) and Al -1.0 mass% Mg2Ge – 0.5 mass% Mg (excess Mg) alloys aged at 523 K were observed by high-resolution transmission electron microscope (HRTEM) to understand their crystal lattices and chemical compositions. Rod-shaped precipitates were parallel to <100> directions of the matrix. There were 2 groups for rod-shaped precipitates in the base alloy, namely, small cross sections about 10 nm and large ones over 20nm in diameter. Small precipitates showed a hexagonal network of bright dots in their HRTEM images, and its crystal lattice was estimated as a hexagonal having a= 0.72 and c= 0.405 nm based on analysis of HRTEM images and selected area electron diffraction (SAED) patterns. This lattice parameter was slight larger than that of the β’-phase in Al-Mg-Si alloy.

Mass thickness determination by use of Bethe sum rule normalization in Eels

1986 ◽  
Vol 44 ◽  
pp. 714-715
Author(s):  
P. A. Crozier ◽  
R. F. Egerton
Keyword(s):  
Electron Scattering ◽  
Cross Sections ◽  
Analytical Electron Microscopy ◽  
Sum Rule ◽  
Mass Thickness ◽  
Relative Cross Section ◽  
Analytical Electron ◽  
Scattering Cross Sections ◽  
Micro Analysis

In analytical electron microscopy it is desirable to have a method of determining the local mass thickness of a sample. One area where this is of importance is in the experimental determination of the electron scattering cross-sections required in EELS micro-analysis. For several years, the Bethe sum rule has been used to place relative cross-section measurements from gases on an absolute scale. We have applied this method to the energy loss spectra recorded frcm thin films in the electron microscope.

The effect of furnace tube material on the oxidation of an Fe10%Cr alloy at 600°C

1980 ◽  
Vol 20 (3) ◽  
pp. 457-460 ◽  
Author(s):  
J.E. Rhoades-Brown ◽  
S.R.J. Saunders
Keyword(s):  
Tube Material ◽  
Furnace Tube
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