scholarly journals Estimation of Oxidation Kinetics and Oxide Scale Void Position of Ferritic-Martensitic Steels in Supercritical Water

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Li Sun ◽  
Weiping Yan
Keyword(s):  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Oxide Scale ◽  
Supercritical Water ◽  
Oxidation Kinetics ◽  
Ternary Phase Diagram ◽  
Measurement Data ◽  
Oxide Scales ◽  
Martensitic Steels ◽  
Iron Diffusion

Exfoliation of oxide scales from high-temperature heating surfaces of power boilers threatened the safety of supercritical power generating units. According to available space model, the oxidation kinetics of two ferritic-martensitic steels are developed to predict in supercritical water at 400°C, 500°C, and 600°C. The iron diffusion coefficients in magnetite and Fe-Cr spinel are extrapolated from studies of Backhaus and Töpfer. According to Fe-Cr-O ternary phase diagram, oxygen partial pressure at the steel/Fe-Cr spinel oxide interface is determined. The oxygen partial pressure at the magnetite/supercritical water interface meets the equivalent oxygen partial pressure when system equilibrium has been attained. The relative error between calculated values and experimental values is analyzed and the reasons of error are suggested. The research results show that the results of simulation at 600°C are approximately close to experimental results. The iron diffusion coefficient is discontinuous in the duplex scale of two ferritic-martensitic steels. The simulation results of thicknesses of the oxide scale on tubes (T91) of final superheater of a 600 MW supercritical boiler are compared with field measurement data and calculation results by Adrian’s method. The calculated void positions of oxide scales are in good agreement with a cross-sectional SEM image of the oxide layers.

scholarly journals Analysis of oxide scale thickness and pores position of HCM12A steel in supercritical water

2021 ◽  
Vol 40 (1) ◽  
pp. 53-65
Author(s):  
Li Sun ◽  
Weiping Yan
Keyword(s):  
Diffusion Coefficient ◽  
Oxide Scale ◽  
Supercritical Water ◽  
Heating Surface ◽  
Oxidation Mechanism ◽  
Oxygen Activity ◽  
Oxide Scales ◽  
Spinel Layer ◽  
Magnetite Layer ◽  
Iron Diffusion

Abstract More attention has been paid to the exfoliation of oxide scale on high-temperature heating surface of utility boiler. The oxidation mechanism of HCM12A steel in supercritical water is proposed and the growth of oxide film is simulated. The duplex scale contains an outer magnetite layer and an inner Cr-rich spinel layer. According to the data of Backhaus and Töpfer, the diffusion coefficient values of iron in magnetite layer are discussed and the function of R V, R I {R}_{\text{I}} for oxygen activity can be used for calculation of iron diffusion coefficients in Cr-rich spinel layer. Based on Wagner’s oxidation theory, the oxidation rate constants of HCM12A are calculated at 500 and 600°C in supercritical water, compared with experimental data of the relevant literatures. The oxygen activities at the interfaces of alloy/Cr-rich spinel oxide and magnetite/supercritical water are estimated. The simulation results of weight gain are matched with the test data. The iron diffusion mechanisms inside the magnetite layer and the Cr-rich spinel layer are analyzed. The iron diffusion coefficient at the interface of Cr-rich spinel/magnetite is discontinuous, while the oxygen activity is continuous in the whole double layer. The thickness of oxide scale on inner tube walls of the final superheater coils (T91) of a 600 MW supercritical boiler is calculated by using the calculation method provided by the paper. The modeling results, the measured data, and the calculation results by the method are compared. Accurate calculation of the thickness of the inner and outer oxide scales can provide a necessary basis for predicting the stress and exfoliation of oxide scales.

Oxidation of Single-Crystal γ′-Ni3A1 at Low Oxygen Partial Pressure

1990 ◽  
Vol 213 ◽  
Author(s):  
E. Schumann ◽  
G. Schnotz ◽  
U. Salzberger ◽  
M. Rühle
Keyword(s):  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Oxide Scale ◽  
Special Technique ◽  
Microstructural Development ◽  
Low Oxygen ◽  
Oxidation Rate Constant ◽  
Fine Grained ◽  
Parabolic Oxidation ◽  
Parabolic Oxidation Rate

ABSTRACTSingle crystals of γ′-Ni3Al((001)-oriented) were oxidized at 1223 K under an oxygen partial pressure of ∼4 ×10−19 atm for times ranging from 0.1 to 50 hours. Microstructural development of the oxide scale and subscale metal was studied by electron microscopy. A special technique permitted the reproducible and efficient preparation of TEM cross section specimens. Initially, a fine-grained γ-Al2O3 scale formed with a preferred orientation. Depletion of Al from the γ′-Ni3Al resultedin a Ni-Al solid solution zone between the oxide scale and the intermetallic. After 20 hours oxidation, a discontinuous α-A12O3 layer between the γ-A12O3 and the metal was observed. The α-A12O3 layer exhibited a much larger grain size than that of the γ-A12O3 and was continuous after 50 hours oxidation. Formation of the α-A12O3 layer correlated with a decreasing parabolic oxidation rate constant kp, as measured by thermogravimetric analysis (TGA).

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.

Oxygen potentials of PuO2-x

2012 ◽  
Vol 1444 ◽  
Author(s):  
Akira Komeno ◽  
Masato Kato ◽  
Shun Hirooka ◽  
Takeo Sunaoshi
Keyword(s):  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Measurement Data ◽  
Approximate Equation ◽  
Defect Chemistry ◽  
Thermo Gravimetry ◽  
Metal Ratio ◽  
The Relationship

ABSTRACTOxygen potentials of PuO2-x were measured at temperatures of 1473 - 1873 K by thermo-gravimetry. The oxygen potentials were determined by in situ analysis as functions of oxygen-to-metal ratio and temperature. The measurement data were analyzed on the basis of defect chemistry and an approximate equation was derived to represent the relationship among temperature, oxygen partial pressure, and deviation x in PuO2-x.

Investigation on early formation and evolution of oxide scales on ferritic–martensitic steels in supercritical water

2018 ◽  
Vol 135 ◽  
pp. 136-146 ◽  
Author(s):  
Yanhui Li ◽  
Shuzhong Wang ◽  
Panpan Sun ◽  
Jiaoqiao Yang ◽  
Xingying Tang ◽  
...  
Keyword(s):  
Supercritical Water ◽  
Oxide Scales ◽  
Martensitic Steels ◽  
Early Formation ◽  
Formation And Evolution

Modeling Investigation of the Oxidation Kinetics of Copper and Aluminum Alloys

2011 ◽  
Vol 402 ◽  
pp. 17-21 ◽  
Author(s):  
Feng Jin ◽  
Qun Luo ◽  
Biao Zhou ◽  
Qian Li
Keyword(s):  
Activation Energy ◽  
Aluminum Alloy ◽  
Aluminum Alloys ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Power Law ◽  
Oxidation Kinetics ◽  
Oxidation Rate ◽  
Calculation Results ◽  
Kinetics Of

The oxidation kinetics of copper or aluminum added with magnesium was investigated by a modified Chou model. The effect of the addition of magnesium in copper or aluminum was discussed. The calculation results showed that the activation energy of CuMg0.34 was the highest among Cu-Mg alloys at 600-900 °C, which indicated that it had the best oxidation resistance in all of the samples. The aluminum alloy AA3004 containing 1.0 wt.% Mg showed the better anti-oxide behavior than AA5182 with 4.0 wt.% Mg, and the relation between oxidation rate and oxygen partial pressure could be expressed as 0.71 times power law.

Corrosion Behavior of Steels in Lead-Bismuth Eutectic: In Stagnant LBE Test at Low Oxygen Partial Pressure

2004 ◽  
Author(s):  
Tomohiro Furukawa ◽  
Eiichi Yoshida ◽  
Kazumi Aoto
Keyword(s):  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Corrosion Behavior ◽  
Chromium Concentration ◽  
Martensitic Steels ◽  
Low Oxygen ◽  
Chromium Oxide Layer ◽  
Thin Chromium ◽  
Lead Bismuth Eutectic ◽  
The Difference

Corrosion test of three chromium-molybdenum steels — 2.25Cr-1Mo, Mod.9Cr-1Mo and 12Cr-steel (ASME P122) — has been performed in stagnant lead–bismuth eutectic (LBE) at low oxygen partial pressure at 550 °C up to 2,000 hours. After the test, the specimens were metallurgically examined using a scanning electron microscopy. All steels had good resistance to LBE under this test condition, and the difference of the effect of chromium concentration in the steels on corrosion behavior was not observed. Corrosion depth of the steels was a few microns, and chromium solution into LBE was observed on the surface. Very thin chromium oxide layer was partly observed on the surfaces of all steels. At the area, no corrosion was occurred. The behavior was the same as the results of martensitic steels tested in stagnant LBE containing 10−7 wt% to 10−8 wt% of oxygen.

Oxidation Kinetics of Steels Utilized in the Production of Valves in Automobile Industry

2012 ◽  
Vol 31 (6) ◽  
pp. 775-779 ◽  
Author(s):  
Z. Grzesik ◽  
Z. Jurasz ◽  
K. Adamaszek ◽  
S. Mrowec
Keyword(s):  
Phase Composition ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Oxidation Resistance ◽  
Automobile Industry ◽  
Oxidation Kinetics ◽  
Chromium Content ◽  
Chromium Concentration ◽  
Oxidation Rates ◽  
Kinetics Of

AbstractThe oxidation kinetics of four Fe-Cr-Mn-Ni based steels, utilized in automobile industry, have been studied as a function of temperature (973–1273 K) and oxygen partial pressure (5–105 Pa). It has been shown that the rate of corrosion of these steels under isothermal conditions is determined by diffusion of reagents through the scale, which phase composition and morphology depend first of all on chromium and to some extend also on nickel and manganese contents. The highest oxidation resistance at high temperatures is observed in the case of the X33CrNiMn23-8 steel, containing highest chromium concentration, equal 23.4 wt.% and nickel equal 7.8 wt.%. The remaining three steels with virtually the same chromium content (≈20 wt.%), but lower than that in the first one, show comparable oxidation resistance. Small differences in the oxidation rates of these three steels may be related to different nickel and manganese contents. It has been found also that the rate of corrosion of all steels under investigation does not depend under steady state conditions on oxygen partial pressure.

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