Oxidation Of Steel Research Articles

Water vapor effects on the oxidation resistance of modified potassium silicate coating at high temperature

An inorganic potassium silicate coating with pigments of alumina, aluminum phosphate, NiCrAlY and copper chromite black was prepared on CB2 stainless steel. Oxidation behavior in either ambient air or O2+H2O mixture at 630 °C for 2000 h was comparatively studied, and the coating exhibited excellent resistance under both test conditions. The water vapor considerably accelerated the oxidation of the uncoated CB2 steel, as the hydroxide, the main constituent of the coating, had a negligible evaporation rate at test temperature, while it had a limited effect on the coated sample. Meanwhile, the existence of coating may prolong or eliminate the incubation period in the O2+H2O mixture at 630 °C. After oxidation, the coating matrix is in an amorphous state and fillers as alumina and copper chromite black are stable in the coating. Leucite (KAlSi2O6) formed by Al from NiCrAlY and potassium silicate in the coatings was detected after tests either in O2 or O2+H2O mixture.

Oxide Inclusions in Aluminum-deoxidized Ultra-low CarbonSteel

RH (Ruhrstahl-Heraeus) degassing process was confirmed to be an effective method for making the steel cleaner by comparing the samples before and after RH degassing, mainly on the area of the total inclusion, the total number of inclusions, the mean area of inclusions, and inclusion size distribution. Four main types of inclusions including alumina and titanium oxides, and Al-Ti-O complex oxides were studied by analyzing their formation mechanisms, compositions, and morphology using SEM (scanning electron microscope) and EDS (energy-dispersive X-ray spectroscopy). Thermodynamic analysis through kinetic simulations of the different stages of RH degassing was conducted by the FactSageTM software package. Based on the equilibrium amount of oxides in the liquid steel, the effects of system temperature, oxygen contents, and alloy additions on the formation of inclusions and nozzle clogging were discussed to improve the steel’s cleanliness.

High‐Temperature Oxidation of 60Si2Mn Spring Steel in Dry Air and Wet Air: Insights from an Experimental and First‐Principles Study

During the hot‐rolling process, the 60Si2Mn spring steel is exposed to both dry air and water vapor at high temperatures. However, no precise mechanism or theory is developed to explain the effect of water vapor on the oxide layer from a microscopic atomic perspective. The high‐temperature oxidation of 60Si2Mn spring steel with dry and wet air is investigated herein using a combination of experiments and first‐principles calculations. After high‐temperature oxidation in both dry and wet air, the 60Si2Mn spring steel generates a typical three‐layer structure consisting of Fe2O3, Fe3O4, and FeO + SiO2/Fe2SiO4; however, the oxide layer produced in wet air is significantly thicker. Furthermore, the phase transformation from Fe3O4 to Fe2O3 occurs in the middle Fe3O4 layer, which is associated with H protons derived from H2O molecules penetrating into oxide layers and promoting the development of Fe vacancies in the center of the tetrahedral interstices. The high porosity of the Fe3O4 layer essentially encourages Fe and O diffusion, hence enhancing the growth of the oxide layer and facilitating the transformation from Fe3O4 to Fe2O3. These findings provide a more detailed mechanistic explanation of how water vapor affects the high‐temperature oxidation of 60Si2Mn spring steel at the atomic level.

TiO2- geopolymer based novel corrosion protective micro-coatings to emaciate mild steel oxidation in severe environments

Now-a-days, cementitious geopolymer coatings are one of the most studied and adaptable coating systems to combat corrosion on low-carbon steel/structural steel. Due to its green and sustainable nature, it has enormous potential to partially replace traditional organic coatings in terms of corrosion resistant properties and economic aspects. Herein, corrosion protection and antibacterial efficiency of titanium oxide (micro-sized, 5/10/15%) containing sodium aluminosilicate (N-A-S-H) geopolymer coating for mild steel is reported to enhance the lifetime of structural steel. Developed coatings were characterized using XRD, FTIR and FESEM. Characterization results indicated the presence of titanium containing new inorganic phase (Sodium titanium oxide hydrate) along with sodium aluminium hydrate phases in XRD, supported by Ti-O stretching vibrations in FTIR along with Si-O-Al stretching vibrations. Microstructural studies using FESEM indicated the uniform distribution of TiO2 in NA-S-H gel matrix. Results revealed that developed coatings depicted corrosion protective characteristics and exhibited adhesion strength between 16.14 and 17.3 MPa. The scratch resistance test revealed that the coating could bear a point load of greater than 5 kg. Minimum percentage weight change and adhesion loss were observed for coating after immersion in NaCl/H2O for 119 days. An accelerated corrosion test (ASTM B117) was performed in the salt environment for 500 h and the best corrosion protective performance was observed for coating formulation containing 10 % TiO2 with maximum rust grading 5. Electrochemical studies showed better corrosion resistance performance for coating formulation containing 10 % TiO2 as compared to the other two formulations containing 5 and 15% TiO2. The antibacterial efficiency of coatings was evaluated by colony count assay (viability method) against the most commonly found gram-positive bacteria Staphylococcus aureus and one gram-negative bacteria Escherichia coli. All three TiO2-incorporated geopolymer coating formulations revealed a good bacterial reduction in percentage with the best performance observed for coating formulation containing 15% TiO2. The accelerated weathering test (ASTM G154-500 h) was performed to ensure the durability and stability of the developed formation. This study developed a novel, environment-friendly, and lucrative cementitious coating material which is potentially suitable for preventing early oxidation and bacterial fouling of mild steel structures.

Hot oxidation and corrosion behaviour of boiler steel fabricated by wire arc additive manufacturing

Boiler Steels undergo severe degradation in corrosion resistance due to oxide scale formation at elevated temperatures. In this study, the comparative hot oxidation and hot corrosion resistance of wire arc additive manufactured SS 308L (WAAM 308L) was examined in hot air and Na2SO4–60% V2O5 molten salt environments at 700 °C. The corrosion resistance at elevated temperature was analysed using thermo-kinetic curves, corrosion products, and morphology of the oxides. The hot oxidation kinetics revealed that WAAM processed SS 308L specimens has excellent resistance and the weight gain reached 3.10 mg/cm2 with thinner oxide scale formation. Hot corrosion kinetics of WAAM processed SS 308L specimens highlighted the higher weight gain (37.0 mg/cm2) in molten salt environment and is attributed to the acceleration of oxide scale formation by the salts at elevated temperatures. Also, the development of Ni3V2O8 and Fe2O3 along with the depletion of Cr2O3 significantly influenced the corrosion resistance at elevated temperatures. The findings of this study reveal the potential of WAAM to produce customized parts for high-temperature applications.

Clarifying the irradiation effect on the general oxidation of 316L stainless steel in high temperature hydrogenated water after 1000h immersion

The role of proton irradiation in the general oxidation of 316 L stainless steel in simulated PWR primary water after 1000 h immersion was clarified by comparing the microstructural and microchemical features of oxides formed on both the irradiated and un-irradiated regions of identical grains. Hence, the interference from differences in crystallographic orientation can be ruled out. Interestingly, the average inner oxide thickness on the irradiated region is significantly thinner than that on the un-irradiated region. The enhanced resistance to oxidation on the irradiated region originates from the more protective inner oxide layer and the formation of a continuous Ni-rich zone near the oxide/matrix interface. The inner oxide formed on irradiated region is less deficient in cation due to the enhanced diffusion of Cr from matrix by the irradiation-induced defects, thus making a better diffusion barrier. Meanwhile, the formation of continuous Ni-rich zone near the oxide/matrix interface, which is facilitated by the Ni-rich defects serving as nuclei, fast generation of vacancy at the interface and suppression of the outward diffusion of surplus Ni, can diminish the available space for the growth of inner oxide. The limited oxidation space and high Cr content at the oxide/matrix interface in the irradiated region result in the formation of rocksalt oxide while spinel oxide is formed near the interface in the un-irradiated region.

Predicting the parabolic growth rate constant for high-temperature oxidation of steels using machine learning models

The parabolic growth rate constant (kp) of high-temperature oxidation of steels is predicted via a data analytics approach. Four machine learning models including Artificial Neural Networks, Random Forest, k-Nearest Neighbors, and Support Vector Regression are trained to establish the relations between the input features (composition and temperature) and the target value (kp). The models are evaluated by the indices: Mean Absolute Error, Mean Squared Error, Root Mean Squared Error and Coefficient of Determination. The steel composition regarding Cr and Ni content and the temperature were the most significant input features controlling the oxidation kinetics.

Effect of Batch-Annealing Temperature on Oxidation of 22MnB5 Steel during Austenitizing

In this paper, the effect of batch-annealing temperature on the oxidation of 22MnB5 steel during austenitizing was studied. When the batch-annealing temperature was decreased from 690 to 680 °C, the surface roughness of cold-rolled 22MnB5 steel decreased, which reduced the oxide layer thickness during the subsequent austenitizing process and had little effect on the mechanical properties in the cold-rolled and quenched state. This indicated that oxidation during austenitizing could be reduced by properly reducing the batch-annealing temperature without affecting the mechanical properties.

Oxidation and Electrical Property Studies on Ferritic Steels as Potential Interconnects in Electrochemical Devices for Energy Conversion

This work presents the results of oxidation studies on commercially available Nirosta 4016/1.4016 ferritic steel, which contains 16.3 wt.% chromium, as well as the electrical properties of steel/scale layer systems in order to determine the usefulness of this steel for constructing metallic interconnects in solid oxide fuel cell (SOFC) and solid oxide electrolyzer cell (SOEC) stacks. The E-Brite ferritic steel, consisting of up to 26 wt.% chromium, was chosen as a reference material. High-temperature isothermal oxidation kinetics studies were carried out on both steels at 1073 K for 255, 505, 760 and 1010 h in air atmosphere. These conditions are representative of those present in the cathode compartment of a SOFC and the anode compartment of a SOEC. Area specific resistance (ASR) measurements were performed on steel/scale layer systems, obtained after the previous oxidation of both steels in the above-mentioned conditions, in the air in the temperature range of 573–1073 K using the pseudo-DC four-probe method. On the basis of these studies, complemented by morphology observations, as well as chemical and phase composition analysis of the oxidation products, the usefulness of Nirosta 4016/1.4016 ferritic steel for manufacturing interconnects in energy conversion electrochemical devices operating at 1073 K was confirmed.

Determination of Experimental Method for Al<sub>2</sub>O<sub>3</sub> Clogging under Near Working Conditions

Negative pressure inside submerged entry nozzle (SEN) during continuous casting process will cause the external air to enter the SEN to cause the secondary oxidation of the molten steel and accelerate the SEN clogging. Based on it, this paper innovatively designed an Al2O3 clogging experimental method under near working conditions, and verified its feasibility. Compared with the existing experimental methods, this new experiment method stimulates the working conditions, ensures the stable source, content, and size of Al2O3 inclusions around specimens. The new test method is used to determine that that the calcium stabilized ZrO2 lining had the better anti-clogging effect.

High-Temperature Oxidation of Steel under Linear Flow Rates of Air and Water Vapor—An Experimental Determined Set of Data

High-temperature oxidation phenomena play a crucial role in steel production and processing. The development of new alloying concepts, the modification of production routes due to the decarbonization of steelmaking, and increasing quality demands will additionally stimulate research activities on high-temperature oxidation. Within the scope of this publication, the oxidation behavior of an unalloyed steel was investigated by means of thermogravimetric (TG) and metallographic analysis. The TG measurements were performed with a simultaneous thermal analyzer in combination with a water vapor generator and a mass spectrometer for quality control. Experiments were conducted in a temperature range from 900 to 1200 °C under various oxidation atmospheres, containing synthetic air and water vapor, with different linear flow rates of the oxidizing medium. According to the thermogravimetric data, an evaluation method is introduced to obtain direct kinetic data for linear and parabolic scale growth. The influence of the experimental parameters on high-temperature oxidation is discussed in detail.

Feeder Pipe Oxidation in the Presence of Steam During a Nuclear Reactor Accident

A Canada Deuterium Uranium (CANDU) reactor has hundreds of carbon steel feeder pipes that are connected at one end to the fuel channels at the reactor face and are connected at the other end to the reactor inlet and outlet headers above the reactor. The production of hydrogen gas from metal–water interaction at high temperatures is a major concern during a severe accident in a nuclear reactor. It is generally accepted that the main source of hydrogen gas during a severe accident is the chemical interaction of Zircaloy fuel cladding and the water coolant. However, it has recently been suggested that the amount of hydrogen produced by the oxidation of carbon steel located outside of a CANDU core could exceed that produced by zirconium oxidation. In this work, the linear and parabolic oxidation rate constants of CANDU feeder carbon steel, in the temperature range of 600–1,100°C, were measured to be W/t = 1.806 × 103 exp (− 126,337/RT) and W2/t = 1.879 × 105 exp (− 135,835/RT), respectively. For parabolic steam oxidation beginning at roughly 90 minutes after reaching steady-state heating temperatures, the latter equation should be used. These rates are about a factor of 5–10 greater than oxidation rates measured in 304L stainless steel and in zirconium specimens, meaning that the carbon steel oxidation can be significant in an accident.

Development of a computational thermodynamics EERZ model for the improvement of hot rolled light steel profiles steel refining

Light steel profiles are steels with medium C, Mn and Si contents. In these steels internal cleanness is important for mechanical properties and surface quality, both during hot rolling and during the coating of the final product. Production costs of these steels are defined by the total heat time, from charging the Electric Arc Furnace (EAF) to starting continuous casting. Ladle furnace (LF) processing has a large influence on heat time and costs related to deoxidation, meeting composition requirements with a high yield of oxidizing alloying additions and proper rinsing to promote homogenization and cleanness. Thermodynamics and kinetics control how slag and steel oxidation levels evolve, as well as the evolution of the non-metallic inclusion population since at this stage primary oxides are the main inclusions. A model based on solid thermodynamic and kinetics fundamentals would be extremely useful for the producer of these steels, so that the evolution of the heat in the ladle furnace could be properly understood and, afterward, improve. In this work, we present the development of an “Effective Equilibrium Reaction Zone” (EERZ) for the LF processing of these steels, using a well-established thermodynamic database for metal and slags and a module of commercial computational thermodynamic software. We aim at demonstrating that these easily accessible and useable tools can be very effective to help in industrial process development. Thus, based on three selected industrial heats we adjust the kinetic parameters to describe the processes occurring for tapping from the EAF to releasing the heat for continuous casting. Volumetric mass transfer coefficients, heat transfer coefficients and other less critical variables are adjusted based on these heats and the model is then tested in seven further heats of the same steel grade. Results indicate that it is possible to achieve a good fit of the model to the industrial process and this helps identifying critical process variables to optimize the process schedule of these steels. Furthermore, we identify possible current limitations of the modeling strategy as suggested in the preliminary steps for the development of a EERZ model that may be coupled for on-line use, the support LF operators.

Oxidation of porous stainless steel supports for metal-supported solid oxide electrolysis cells

Oxidation of porous stainless steel supports for metal-supported solid oxide electrolysis cells

Corrosion barrier alumina/zirconia bilayer stack on low Cr steel by direct liquid injection metalorganic chemical vapor deposition

Numerous industrial fields necessitate the development of advanced metallic materials presenting high corrosion resistance in aqueous media and being less expensive than classical high chromium steels. In the present work, amorphous zirconia, alumina and alumina/zirconia coatings have been deposited on 2 wt% chromium steel coupons using an innovative direct liquid injection metal organic chemical vapor deposition process. Scanning electron microscopy and X-ray diffraction reveal that the alumina sublayer acts as an efficient barrier against steel oxidation occurring during the amorphous zirconia deposition performed under O2 at 400 °C. They also show that the steel oxidation occurring concomitantly to the zirconia coating modifies the film morphology by increasing its roughness and thickness, in comparison with the same zirconia coating on alumina. The anticorrosive properties of the thin films have been studied by an immersion test of the bare and coated coupons in deionized water at 80 °C during 6 days and by electrochemical impedance spectroscopy in aqueous sodium chloride solution for 48 h. They reveal that, in contrast to alumina and zirconia monolayers alone, the alumina/zirconia stack acts as a corrosion protection coating in pure water through a synergetic barrier effect against (i) oxidation by alumina and (ii) aqueous corrosion by zirconia.

A Modeling Approach to Understanding the Interrelated Nature of Cathodic Protection Current and AC Stray Current on Pipelines

The change in AC current on a pipeline as a function of cathodic protection (CP) current is well known in the industry as is the change in CP current as a function of the interfering AC current. To better understand the underlying mechanisms responsible for these observations, the interrelated nature of AC and CP was reproduced here for pipeline steel in soil-simulating environments and the results were analyzed within the context of kinetics and transport-based models. The kinetics model combines the Butler-Volmer reaction kinetics for steel oxidation, oxygen reduction, and hydrogen reduction with the time evolution of potential at an interface subject to alternating potentials. The critical observation from these calculations was that changes to the measured CP on a pipeline with AC interference were not due to changes in the underlying electrochemical kinetics, but rather, due to asymmetric polarization of the steel along existing Tafel slopes resulting in a change in the time-averaged DC signal. To explore the effect of CP current on the magnitude of the AC interference, a transport-based model of grounding resistance at pipeline coating holidays was developed. For holiday sizes less than 20 cm2, calculations revealed that at a critical CP current density of 1 A/m2, local soil pH increases rapidly and the normalized grounding resistance decreases. Correspondingly, the corrosion rate increases dramatically.

Influence of various thermal conditions on the composition of high‑temperature diffusion oxides (satellite inclusions) in solid steel

The main goal of any modern production of long products is to ensure the required quality of finished products. One of the important quality indicators, along with mechanical and technological properties, is the quality of the rolled metal surface. The article presents the results of experimental studies of the composition of high‑temperature diffusion oxides formed on the surface of artificially deposited defects under various conditions of temperature exposure using the microrentgenospectral method on a scanning electron microscope with an energy dispersive microanalyzer. The characteristic features in terms of the percentage and presence of certain chemical elements in the scale of various steel grades have been established.

Comparison of Corrosion Behavior of T91, 9Cr and 9CrAl ODS Steels in Liquid Pb

It is important to improve the liquid lead corrosion resistance of fuel cladding alloy for promoting the development of lead-based reactors. The corrosion behaviors of traditional T91 steel and similar oxide dispersion strengthen ODS-type steels with or without the addition of Al, and were examined and compared at 600 °C in static oxygen-controlled liquid Pb in this research. High-temperature liquid lead corrosion tests were carried out for 120 h, 240 h, 500 h, 1000 h, and 2000 h, respectively, for three prepared samples. After the experiment, the corrosion behavior was evaluated and compared mainly based on the aspects of appearance, corrosion depth, microstructure, and composition difference. It was found that just the ODS design did not show a positive effect on corrosion resistance, while the addition of Al is beneficial to improving the corrosion resistance of ODS steel. The maximum corrosion depth of 9CrAl ODS is only 51.8 μm after corrosion for 2000 h, which is much lower than that of 9Cr-ODS steel. A thin film containing Al/Cr formed in the corrosion area after adding Al in 9Cr ODS steel, which played a positive role in corrosion resistance.

Influence of flowing water vapor containing environment on high-temperature behavior of 9Cr creep-resistant steels

Steam superheaters are used to increase the temperature and transport the flowing superheated water vapor before it enters the steam turbine. Creep-resistant steels with required high resistance to high-temperature oxidation are used for production of superheaters. The elimination of the protective oxide layer formation on the steel surface limits their upper application temperature in a water vapor containing environment. In this paper, the oxidation behavior of MarBN (MARtensitic 9Cr steel strengthened by Boron and MX Nitrides) steel exposed for 1000 h at 600 and 650 °C in a mixed atmosphere of air + 10% water vapor was analyzed. The oxidation mechanism was discussed on the basis of oxidation kinetics, morphological observations, microscopic and XRD analysis of the oxide layer. The oxidation kinetics was governed by the parabolic law. SEM analysis and XRD analysis showed that the outer steel oxide layer after 1000 h exposure at 600 °C was mainly composed of hematite Fe2O3 and a small proportion of Cr2O3. The inner oxide layer was composed of (FeMnCr)2O4 and Cr2O3. The steel surface after 1000 h of oxidation at 650 °C, the outer oxide layer consisted of hematite Fe2O3, Cr-rich phase and magnetite Fe3O4, and the inner oxide layer was mainly iron-chromium-manganese spinel (FeMnCr)2O4.

High temperature oxidation behavior of Fe–3.0%Si steel with non-equilibrium reaction

The phase formation-transition process and microstructure evolution of Fe–3%Si steel oxide layers were systematically studied during the high-temperature oxidation process with oxidizing atmosphere when annealed at 1000–1240 °C for 200 min. The micromorphology, oxidation mechanism and crystal structure stability were characterized and discussed combining with the XRD, FESEM and XPS technology. The oxidized scale shows more and more complex multiple layers structure including single layer, double layers and three layers with the increasing of annealing temperature, which attributes to the diffusion effect and oxidation reaction oxygen anions and metal cations. The formation of SiO2, FeO and Fe2SiO4 layer also could inhibit the oxidation reaction of matrix. The oxidized scale mainly shows a single layer structure of Fe2O3 when annealed at 1000–1080 °C, which is easy to peel off from matrix. It shows a double oxide layers structure when annealed at 1080–1120 °C, the loose outer layer contains Fe2O3, and the grid inner layer contain SiO2, FeO and Fe2SiO4 compounds. It shows an outermost, intermediate and inner three layers structure when annealed at 1160–1240 °C. The outermost layer is Fe2O3, the main phases of intermediate layer are FeO and Fe2SiO4 compounds as well as some SiO2 particles, and the inner layer (joint layer) is SiO2.