scholarly journals Steam Oxidation of Austenitic Heat-Resistant Steels TP347H and TP347HFG at 650–800 °C

Materials ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 577 ◽  
Author(s):  
Zhiyuan Liang ◽  
Qinxin Zhao
Keyword(s):  
Oxide Scale ◽  
Steam Oxidation ◽  
Oxidation Products ◽  
Oxide Scales ◽  
Metallic Ions ◽  
Breakaway Oxidation ◽  
Outward Diffusion ◽  
X Ray ◽  
Heat Resistant ◽  
Heat Resistant Steels

Steam oxidation of austenitic heat-resistant steels TP347H and TP347HFG at 650–800 °C was investigated. Comprehensive micro-characterization technologies containing Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDS), X-ray Diffraction (XRD), and X-ray Photoelectron Spectroscopy (XPS) were employed to observe and analyze the oxidation products. Results show that breakaway oxidation behaviors were observed on TP347H at 700 °C and 800 °C. The oxidation kinetics of TP347HFG at 650–800 °C followed a parabolic law. The oxide scales formed on TP347HFG were composed of MnCr2O4 and Cr2O3. A thin and protective Cr-rich oxide scale was replaced by Fe2O3 nodules due to the insufficient outward migration of metallic ions, including Cr and Mn at the subsurface of coarse-grain TP347H. Smaller grain of TP347HFG promoted the formation of the compact Cr-rich oxide scales. At higher temperatures, the incubation period for breakaway oxidation of the Cr-rich oxide scale was much shorter because of quick evaporation of the Cr2O3 oxide scale and the slower outward diffusion of metallic ions via the grain boundaries.

scholarly journals Steam Oxidation of Ferritic Heat-resistant Steels for Ultra Supercritical Boilers

2001 ◽  
Vol 50 (2) ◽  
pp. 50-56 ◽  
Author(s):  
Yutaka Watanabe ◽  
Yongsun Yi ◽  
Tatsuo Kondo ◽  
Koshi Suzuki ◽  
Kimio Kano
Keyword(s):  
Steam Oxidation ◽  
Heat Resistant ◽  
Heat Resistant Steels

Corrosion Behavior of Fe-Cr Alloys in Ar-10%O2 Atmosphere

2011 ◽  
Vol 462-463 ◽  
pp. 1250-1254 ◽  
Author(s):  
Norinsan Kamil Othman ◽  
N. Othman ◽  
Azman Jalar
Keyword(s):  
Oxide Scale ◽  
Oxidation Rate ◽  
Cyclic Oxidation ◽  
Corrosion Behaviour ◽  
Optical Metallography ◽  
Chromia Scale ◽  
X Ray Diffraction ◽  
Breakaway Oxidation ◽  
X Ray ◽  
Cr Content

The corrosion of four Fe-Cr alloys (Cr: 9, 12, 20, and 25%) with different Cr contents were subjected to cyclic oxidation furnace in Ar-10%O2 atmosphere at 950oC for 120 h. The samples after oxidation were investigated by using X-ray diffraction (XRD), optical metallography and SEM/EDS. The results indicated that increasing Cr content reduced the oxidation rate and the scale cracking. Alloys with less Cr content occurred breakaway oxidation due to formation of Fe-rich oxide scale. However, a thin protective chromia scale was observed on alloys with Cr > 20%. The corrosion behaviour on Fe-Cr alloy was then discussed based on experimental observation.

Microstructural Investigation of the Oxide Scale on Zr-2.5NB and its Interface with the Alloy Substrate

1998 ◽  
Vol 550 ◽  
Author(s):  
V. Benezra ◽  
S. Mangin ◽  
M. Treska ◽  
M. Spector ◽  
G. Hunter ◽  
...  
Keyword(s):  
Oxide Scale ◽  
Tetragonal Zirconia ◽  
Oxidation Products ◽  
X Ray Diffraction ◽  
Metal Interface ◽  
Two Phase ◽  
Microstructural Investigation ◽  
X Ray ◽  
Alloy Microstructure

AbstractOxidized Zr-2.5Nb is being developed as an articular bearing surface for the femoral component in total joint arthroplasty. It has so far demonstrated superior wear performance against ultrahigh molecular weight polyethylene (UHMWPE) with respect to traditional articulating materials such as Co-Cr-Mo alloys. In this investigation, we used thermogravimetric analysis, transmission electron microscopy, and in situ x-ray diffraction techniques to study the microstructure and stress state of the oxide scale grown on Zr-2.5Nb.The oxidation temperature not only determines the kinetics of oxidation but the morphology of the various oxidation products. We have identified the oxidation products of both phases of the two phase alloy and correlated them with the original alloy microstructure. These include not only monoclinic zirconia but also small amounts of tetragonal zirconia and a mixed oxide phase combining both zirconium and niobium. The alloy microstructure both influences the final oxidation products and is reflected in the microstructure of the oxide. The oxide scale itself has a predominantly columnar microstructure which extends from the oxide/metal interface to the outer surface of the oxide. In situ x-ray diffraction measurements revealed that the oxide scale is stressed in compression following cooling and exhibits strong crystallographic texture. The oxide/metal interface is continuous, without pores or voids which might be detrimental to oxide adhesion. In addition, we have identified a phase which develops at the interface between the beta-zirconium grains and the oxide. We have also identified amorphous regions within the oxide scale which serve as sinks for silicon and other impurity elements found in the alloy.

Porosity Developments within 9Cr-1Mo Steel Exposed to CO2

2018 ◽  
Vol 941 ◽  
pp. 426-431
Author(s):  
Lawrence Coghlan ◽  
Rebecca L. Higginson ◽  
Mark A.E. Jepson ◽  
Aya Shin ◽  
Jonathan Pearson
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Oxide Scale ◽  
Oxide Scales ◽  
Breakaway Oxidation ◽  
9Cr Steel ◽  
Air Interface ◽  
Duplex Oxide ◽  
Over Time ◽  
Scanning Electron

When 9Cr-1Mo steel is exposed to CO2-rich advance gas-cooled reactor (AGR) gases it forms a duplex oxide which consists of an outer Fe rich layer and an inner Cr rich spinel which provides oxidation resistance allowing the steel to resist the corrosive atmosphere of the plant. The oxide scale develops, growing both into the substrate and outwards from the initial metal/air interface. The spinel develops porosity through the coalescence of Fe vacancies which over time alters the properties of the oxide and potentially allows a transport network to form within the oxide. The porosity of the duplex oxide was measured using scanning electron microscopy of oxides on 9Cr steel samples oxidised in a CO2 atmosphere. Results show that samples which have suffered breakaway oxidation show larger oxide scales with alternating Fe/Cr bands whereas samples which have yet to suffer from breakaway show higher peak porosity values but thinner oxide scales. Furthermore the samples which are currently under protective oxidation show a high max porosity peak in comparison to those which have suffered breakaway.

High Temperature Oxidation of Ti39.4Al10V Alloy

2004 ◽  
Vol 449-452 ◽  
pp. 813-816 ◽  
Author(s):  
Dong Bok Lee ◽  
Y.D. Jang
Keyword(s):  
High Temperature ◽  
Oxide Scale ◽  
Oxidation Resistance ◽  
Mixed Layer ◽  
High Temperature Oxidation ◽  
Oxide Scales ◽  
Temperature Oxidation ◽  
Outward Diffusion

Alloys of Ti39.4Al10V (at.%) that consisted mainly of ordered β-Ti, γ-TiAl and α2-Ti3Al phases were oxidized at 700, 800, 900, and 1000oC in air. The oxide scales formed consisted largely of an outermost, thin TiO2 layer, an outer, thin Al2O3 layer, and an inner, very thick (TiO2+Al2O3) mixed layer. Vanadium, which was uniformly distributed throughout the oxide scale, harmfully decreased oxidation resistance, and made thick, nonadherent scales owing to the formation of low melting compounds of V-oxides. The oxidation progressed via the outward diffusion of Ti, Al and V ions, and the concurrent inward transport of oxygen.

On the spallation of oxide scales in high-strength low-alloy (HSLA) hot-rolled steels

2020 ◽  
Vol 38 (4) ◽  
pp. 355-364
Author(s):  
Nelson F. Garza-Montes-de-Oca ◽  
Arnulfo Treviño-Cubero ◽  
Javier H. Ramírez-Ramírez ◽  
Francisco A. Pérez-González ◽  
Rafael D. Mercado-Solís ◽  
...  
Keyword(s):  
Thermal Stress ◽  
Oxide Scale ◽  
High Strength ◽  
Adhesion Energy ◽  
Oxide Scales ◽  
X Ray Diffraction ◽  
X Ray ◽  
Hsla Steels ◽  
Oxide Spallation ◽  
Hot Rolled

AbstractIn this work, results on the causes that could promote the abnormal spallation of the oxides formed on the surface of high-strength low-alloy (HSLA) steels are presented. By means of Rietveld refining of X-ray diffraction spectra, scanning electron microscopy analyses and calculations, it was found that the value of the thermal stress experienced by the oxide scale reached a maximum when the oxide scale was comprised by 65% wt magnetite Fe3O4 and 24% wt wustite FeO this, due to the incomplete transformation of the latter phase to Fe3O4 and α-Fe from cooling from 670 °C to ambient temperature. Contrarily, it was found that when a balance in the amount of Fe3O4 and FeO was 46.4 and 46.5%wt respectively, the calculated thermal stress was reduced, and oxide spallation was not that severe. The reasons for oxide scale detachment from the surface of the steels are explained in terms of the adhesion energy of the bulk oxide scale, the amount of magnetite Fe3O4 present in the oxides and the chemical composition of the steel particularly the elements chromium and titanium.

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