High Temperature Oxidation Process Research Articles

Preliminary Study on High-Temperature Oxidation of Ni-AlN-TiN/Si3N4 Electrodeposition Composite Coatings

High-temperature oxidation is a serious problem for several materials during their application in aggressive environments, such as high temperatures, high-speed machining, and corrosive environments. This research was conducted to analyze the effect of high-temperature oxidation on the surface morphology of the Ni-AlN-TiN/Si3N4 composite coating. The coatings were electrodeposited at a current of 5 me for 15 minutes and various electrodeposition temperatures of 35°C, 40°C, and 45°C. This composite coating was formed on tungsten carbide substrates with the electrolyte solution consisting of 6 g/L AlN, 6 g/L TiN, 40 g/L H3BO3, 0.6 g/L Si3N4, 0.17 M NiCl2.6H2O, 0.38 M NiSO4.6H2O, and 0.6 g/L Sodium Dodecyl Sulfate. The high-temperature oxidation process was carried out at a temperature of 700°C for 2 hours in the furnace. The surface morphology was characterized by using Scanning Electron Microscopy (SEM). The results showed that the surface morphology of the Ni-AlN-TiN/Si3N4 composite coating deposited at a temperature of 40°C had a scaled growth, reduced cracks, and reduced pore. It was due to the effect of high-temperature treatment.

Gas fuel combustion and related problems

Combustion, as it is well known, is based on chemical reactions. If we look at a clear scientific definition of the term “combustion”, then combustion will be a process of rapid high-temperature oxidation, combining physical and chemical phenomena. Combustion consists of a large number of elementary redox processes leading to the redistribution of valence electrons between atoms of interacting substances.Modern theories of combustion relate flame spreading in gases to chemical chain reactions[1]. Nowadays, in a view of the wide spread of gas, understanding of a ship fuel and analysis of gas related problems of combustion are more and more critical. Gas itself is not able to ignite in a combustion chamber as a conventional fuel just because of compression and temperature rising. It requires a strong and efficient source of fire. The article is focused on analyzing igniting, flame spreading and detonation in a combustion chamber. The detonation condition was assessed in case of using gas as ships fuel.

Molecular dynamics simulation and experimental research on the oxidation reaction of methyl linoleate at low oxygen and high temperature

The pyrolysis and low-oxygen high-temperature oxidation process of methyl linoleate containing two unsaturated double bonds were analyzed by kinetic analysis, density functional theory calculation and ReaxFF-MD considering it as a substitute for biodiesel. The combined system of TG-FTIR-MS was used to analyze the escape characteristics of multi-component gas product during the pyrolysis as well as high-temperature oxidation of methyl linoleate under low-oxygen. The ReaxFF-MD molecular dynamics method was used to analyze the effect of initial reaction path of the thermal decomposition of methyl linoleate and the oxygen content on the oxidation reaction products. The results show that the pyrolysis of methyl linoleate has reaction activation energy of 58.2 kJ/mol, while, for the high-temperature oxidation process under low oxygen, it is 58.79 kJ/mol. The main gaseous products are CO2, CH4, CO/C2H4, H2O and products containing C–H, C–O, CO and other functional groups. Through DFT calculations and ReaxFF-MD, we found that breaking of C–O bond leading to the formation of smaller CH3 radical and decarboxylation to form CO2 constitute the initiation mechanism for the pyrolysis of methyl linoleate pyrolysis and high-temperature oxidation in presence of low oxygen. The double bond of methyl linoleate is prone to generate C7H10 intermediates with higher carbon content during the pyrolysis process. At the same time, through simulation, we found that oxygen and fuel are mixed as soon as possible at the beginning of the combustion of methyl linoleate which helps to reduce the production of C2 products from the pyrolysis of methyl linoleate.

High Temperature Oxidation Behavior of an Equimolar Cr-Mn-Fe-Co High-Entropy Alloy.

The oxidation behavior of an equimolar Cr-Mn-Fe-Co high-entropy alloy (HEA) processed by 3D laser printing was investigated at 700 °C and 900 °C. The oxidation kinetics of the alloy followed the parabolic rate law, and the oxidation rate constant increased with the rising of the temperature. Inward diffusion of oxygen and outward diffusion of cations took place during the high-temperature oxidation process. A spinel-type oxide was formed on the surface, and the thickness of the oxide layer increased with the rising of experimental temperature or time. The exfoliation of the oxide layer took place when the test was operated at 900 °C over 12 h. During oxidation tests, the matrix was propped open by oxides and was segmented into small pieces. The formation of loose structures had great effects on the high-temperature oxidation resistance of the HEA.

High temperature oxidation of monolayer MoS2 and its effect on mechanical properties: A ReaxFF molecular dynamics study

Molybdenum disulfide (MoS2) has lately been at the epicenter of scientific research due to its mesmerizing electronic, thermal, and physical properties, which have opened the door to a cornucopia of applications, including an efficient electrocatalyst, solid lubricant in satellites, and advanced electronics. Unfortunately, unavoidable high-temperature exposure to terrestrial environments can results in the oxidation of MoS2, thus deteriorating its surface chemistry and mechanical stability. For this reason, a fundamental understanding of the high-temperature oxidation mechanism of MoS2 and its mechanical stability is vitally important for real-world applications. Here, we used reactive molecular dynamics (RMD) simulations based on ReaxFF, one of the most effective computational methodologies, to investigate the atomic level high-temperature oxidation process on the basal surface of MoS2 and its impact on mechanical properties and fracture mechanics for the first time. First, we thoroughly studied the oxidation kinetics of MoS2 at 1400 K, 1500 K, and 1800 K temperatures. We revealed that MoS2 readily reacts with O2 above 1500 K. Oxidation started by the adsorption of O2 on the top of S atoms and culminated in the formation of oxy-sulfide (MoS2-xOx) solid solution. Tensile simulation results unveiled that oxidation notably degrades the mechanical properties of MoS2, such as fracture strength, fracture strain, Young's modulus, and fracture toughness. Interestingly, both pristine and oxidized MoS2 experienced a phase transition from trigonal prismatic (2H-MoS2) to metallic distorted octahedral (1T-MoS2) phase. Finally, we disclosed the fracture process of pristine and oxidized MoS2 samples from atomic trajectories. This study would lay the cornerstone for successfully realizing MoS2 in high-temperature functional systems as well as serving as a solid roadmap for engineering its chemical and mechanical properties.

A novel experimental setup for in situ oxidation behavior study of Nb/Hf/Ti (C-103) alloy for high temperature environments

In this study, a novel perspective method was attempted to understand the oxidation behavior of Nb/Hf/Ti (C-103) alloy at high temperature environment through in situ oxidation resistance measurement with respect to temperature and time. Electrochemical impedance spectroscopy (EIS) was employed to determine the oxidation behavior of C-103 alloy at different temperatures. Structural and chemical properties of heat treated samples were characterized by X-ray diffraction (XRD), scanning electron microscope and energy dispersive X-ray spectroscopy (SEM/EDX). EIS studies revealed that charge transfer resistance (Rct) is decreasing and at the same time current density is increasing with increasing temperature and time during high temperature oxidation process. Also, C-103 alloy obey parabolic law of corrosion during rapid heat treatment process.

Experimental Study on Sulfur Deactivation and Regeneration of Ni-Based Catalyst in Dry Reforming of Biogas

The dry reforming of methane (DRM) using biogas and a Ni-based catalyst for syngas production was studied experimentally in this study under the presence of H2S. Using the nonpoisoned DRM performance as a comparison basis, it was found that the catalyst deactivation by the sulfur chemisorption onto the catalyst surface depends on both reaction temperature and time. With low reaction temperatures, a complete sulfur coverage was resulted and could not be regenerated. With higher reaction temperatures, the H2S coverage decreased, and the poisoned catalysts could be regenerated. The experimental results also indicated that a catalyst deactivation could not be avoided by using the bi-reforming of methane by adding O2 or H2O simultaneously in the reactant due to the stronger chemisorption capability of sulfur. The catalyst could only be regenerated after it was poisoned. The experimental results indicated that the high-temperature oxidation process was the most effective process for regenerating the poisoned catalyst.

Initial oxidation of Ni-based superalloy and its dynamic microscopic mechanisms: The interface junction initiated outwards oxidation

Understanding the high-temperature initial oxidation mechanism and its dynamic processes is generally important because a small amount of initial oxidation can induce rapid corrosion and cause catastrophic failure. We reveal the mechanism of initial oxidation in a third-generation Ni-based superalloy by in situ visualizations and investigations of the nano- and atomic-scale dynamic processes from room temperature to 900 °C with a Cs-corrected environmental transmission electron microscope. The initial oxidation starts from the γ/γ′ interface at low temperatures. The high-temperature oxidation process with deficient oxygen prefers oxidation sites at the cross-junctions of the γ/γ′ interfaces. The growth rate of the oxide nanoparticles depends on the oxidation temperatures, with a low rate below 600 °C and a rapid-growth speed at temperatures higher than 700 °C. Mass transfer from the γ′ and γ phases to the γ/γ′ interface, particularly at the cross-junctions of these interfaces, is observed to cause oxide accumulation. This study provides a direct observation of the interphase, interface-junction-initiated outward oxidization including Al and Cr elements. These results shed light on the initial oxidation mechanisms of materials containing a second phase with interphase interfaces and the materials at deficient oxygen conditions as well as those with protection coating layers.

OXIDATION KINETIC AND ANODIC BEHAVIOR OF Zn22Al ALLOY DOPED WITH NICKEL

The article presents the results of the study of the oxidation kinetics and the anodic behavior of the zinc-aluminum alloy Zn22Al, doped with nickel, in various corrosive environments. The kinetic and energy parameters of the process of high-temperature oxidation of alloys are determined. It is shown that the process of high-temperature oxidation of samples of Zn22Al-Ni alloys is characterized by a monotonic decrease in the true oxidation rate and an increase in the effective activation energy at the content of the alloying component in the initial Zn0.5Al alloy up to 0.5 wt.%. It was found that nickel additives within the studied concentration (0.01-0.5 wt.% ) slightly increases the oxidability of the base alloy Zn22Al at temperatures of 523, 573 and 623 K. It is shown that the dependence of the corrosion potential of zinc-aluminum alloys on the nickel content in them is of the same type, i.e. the additives of the alloying component contribute to the displacement of the corrosion potential in the region of positive values. The influence of the aggressiveness of the corrosive medium on the anodic behavior of alloys when comparing concentrated electrolytes with the increasing concentration of chloride ions in the sodium chloride solution is established. It is determined that the potentials of pitting formation and repassivation of the initial alloys shift to a more positive region with an increase in the nickel concentration in the alloys. The greatest shift of these potentials to the positive region is observed when alloying alloys containing small nickel additives. It is shown that the corrosion products of the studied alloys consist of a mixture of protective oxide films Al2O3, ZnO, NiO, Al2O3·ZnO and Al2O3·Ni2O3. It was found that the alloying of zinc-aluminum alloys with nickel (in the range of 0.01–0.05 wt.%) reduces the corrosion rate of the base alloy by 2-3 times. The proposed alloy compositions can be used as an anode coating for corrosion protection of steel products and structures.

Effect of Y2O3 Addition on High-Temperature Oxidation of Binderless Tungsten Carbide

High-temperature oxidation tests were carried out on binderless tungsten carbide (WC) with different Y2O3 contents (0, 1, 2, 3, and 4 wt.%) and on YG3 cemented carbide. Results demonstrated that the addition of Y2O3 led to a significant improvement in the high-temperature oxidation resistance of binderless tungsten carbide compared with those of YG3 cemented carbide and pure tungsten carbide. After oxidation at 800°C for 120 min, the oxidation weight gain of binderless tungsten carbide with 1 wt.% Y2O3 was 58.54 mg cm−2, corresponding to the reduction by 47.7% compared with YG3 cemented carbide. In the high temperature oxidation process, WC in the triangle grain boundary was first oxidized to Y2WO6 due to the high activity of Y2O3 which is present mainly in the WC grain boundaries. The transport of W4+ outward along the grain boundary and the diffusion of O2− inward along the grain boundary were hindered by Y2WO6 with the high ionic radius and thus the antioxidant capacity of binderless tungsten carbide was improved. Meanwhile, the adhesive ability of oxidation layer on the substrate was enhanced with the “pinning effect” of Y2WO6, which also led to the improvement of oxidation resistance. With the Y2O3 content increasing from 1 to 4 wt.%, the antioxidant properties of binderless tungsten carbide gradually declined, and the antioxidant performance of binderless tungsten carbide with 1 wt.% Y2O3 was found to be the best.

Augmentation of Aluminum and Boron Ignition

Effect of K2CO3 and KCl additives on the process of high-temperature oxidation and ignition of conglomerates of powdered boron and aluminum particles and on the critical conditions for the ignition of particle–gas mixtures of these metals is studied experimentally. It is revealed that the mixtures of boron and aluminum particles covered (encapsulated) with salts ignite at temperatures lower than the ignition temperatures of mechanical mixtures of metals with these salts in appropriate proportions and significantly lower ignition temperatures of pure boron and aluminum. This indicates the active role of salts in the process of heterogeneous ignition. It is established that, for boron conglomerates, the accelerating effect of salt additives on the oxidation of conglomerates is noticeable at all investigated concentrations and compositions starting from 1% (by weight). For aluminum, an increase in the reaction rate is noticeable only for KCl additives at concentrations of 3% and above.

Synchronous Growth of Porous MgO and Half-Embedded Nano-Ru on a Mg Plate: A Monolithic Catalyst for Fast Hydrogen Production

Development of efficient and sustainable monolithic catalysts for NaBH4 hydrolysis remains an important goal for hydrogen cycling. In this work, the structured catalyst Ru/MgO with an on–off feature has been prepared by directly growing a nano-Ru-embedded MgO coating layer on a Mg substrate via an instant high-temperature plasma oxidation process. The porous MgO framework provides an ideal space for the access of reactants and diffusion of mass transport, which facilitates reaction triggering and the expulsion of byproducts to avoid poisoning the catalyst. Importantly, Ru nanoparticles (NPs) are monodisperse with ultrasmall particle size deriving from a concurrent rapid arcing and fast quenching. The hierarchical structured Ru NP catalysts are highly active for hydrolysis of sodium borohydride by achieving a high hydrogen generation rate (HGR) of 101,189 mL min–1 g–1 and exhibit attractive stability. In addition, it is facile to realize the “on–off” functionality based on simple separation that could accurately control the hydrogen generation, suggesting the structured catalyst to be of great potential for practical applications. This simple method opens valuable opportunities for fast synthesis of the high-quality structured catalyst and could be extended to various noble metals on oxides of valve metals with high catalytic performance.

Effect of Heat Treatment on Structure and Oxidation Resistance of Flame-Sprayed Ni-20 wt.% Al on Carbon Steel

In this study, the effects of time and temperature of heat treatment on Ni-20 wt.% Al flame spraying coatings were studied. The objectives are to find the optimal sample in terms of microstructure and compare its oxidation resistance with the as-sprayed coating. The coatings were deposited by flame spraying on low carbon (St 37) steel substrate. The specimens were heat-treated in vacuum at 850 °C and 950 °C for 1 h and at 1050 °C for 1, 3, and 6 h. Microstructural characterization and phase analysis were performed by scanning electron microscopy, energy-dispersive spectrometry, and x-ray diffraction, respectively. The results showed that the lowest porosity (0.43 %) and the highest NiAl content were achieved for the sample heat-treated at 1050 °C for 1 h. Optimized heat-treated, as-sprayed, and bare steel specimens were exposed to ambient air at 800 °C in order to evaluate their durability and oxidation resistance. The results showed that their oxidation rate constants were 24.66, 65.06, and 269.42, respectively. Most of the NiAl content in the coating was responsible for covering the coating surface by a protective γ-Al2O3 layer during the high-temperature oxidation process.

HIGH TEMPERATURE AND ELECTROCHEMICAL CORROSION OF Zn0.5Al ALLOY DOPED WITH CALCIUM IN VARIOUS MEDIA

The article presents the results of a study of high-temperature and electrochemical corrosion of Zn0.5Al alloy doped with calcium in the various media. The thermogravimetric method was used to study the interaction of the Zn0.5Al alloy doped with calcium with atmospheric oxygen in the temperature range 523–623 K in the solid state. The kinetic and energy parameters of the process of high-temperature oxidation of alloys are determined. The process of high-temperature oxidation of Zn-Al-Ca alloys system is characterized by a monotonic decrease in the true oxidation rate and an increase in the effective activation energy when the alloying component in the initial Zn0.5Al alloy is up to 1.0 wt% doping with zinc-aluminum alloy 0.5 and 1.0 wt%. Calcium shows a slight increase in the oxidation rate of alloys. It was revealed that the oxidation process of the studied alloys with oxygen of the gas phase obeys the hyperbolic law. It was found that calcium supplements in the range of 0.01 - 0.1 wt%. The oxidizability of the initial Zn0.5Al alloy is reduced significantly, and the oxidation products of the alloys were ZnO, Al2O3, Al2O3 ∙ ZnO, CaO, Al2O3 ∙ CaO. By potentiostatic methods in the potentiodynamic mode with a potential sweep speed of 2 mV/s, it has been shown that for all samples of the Zn0.5Al-Ca alloys system in the acidic, neutral, and alkaline media, electrochemical potentials of corrosion, pitting formation, and repassivation are shifted to the region of negative values. It was revealed that zinc-aluminum alloys doped with calcium are most resistant to pitting corrosion in all studied media, respectively, in acidic (0.01n.), neutral (0.03-, 0.3-, 3.0 wt%) and alkaline (0.01n.) electrolytes of HCl, NaCl and NaOH. It has been established that calcium additions in the range of 0.01 - 0.1 wt.% reduce the corrosion rate of zinc-aluminum alloy Zn0.5Al by a factor of 2–3. Calcium alloys are recommended as anodic coatings and protectors for corrosion protection of steel products and structures operating at high temperatures.

Enhanced Corrosion Resistance of an Alumina-forming Austenitic Steel Against Molten Al

The development of corrosion resistant steel for molten Al has always attracted the interests from die casting industry for several decades. In this paper, we reported the enhanced corrosion resistance in 750 °C molten Al of an alumina-forming austenitic steel (AFA) via deliberately producing oxide layer after different high-temperature oxidation processes. The results showed that the corrosion resistance against molten Al of the AFA was improved significantly due to the presence of a stable, compact and continuous oxides barrier, in comparison with H13 tool steel as well as unoxidized AFA without Al2O3 film. Apparently, the non-wetting α-Al2O3 film, which was formed after high-temperature oxidation, effectively protected the substrate from inner-diffusion and penetration of the molten Al. These findings provide one of cost-effective ways to improve the corrosion resistance of steels against molten Al.

Effect of Ultrasonic Shot Peening on Oxidation Behavior of T91 and SS347 Steels in Air and Steam at 650 °C

Ultrasonic shot peening (USP) is a relatively new process of surface modification to improve mechanical properties as well as corrosion and high-temperature oxidation resistance of metallic materials. The effect of USP on surface properties and the process of high-temperature oxidation in air and steam environment, following USP of the T91 and SS347 steels, was studied in this investigation. Surface modification by USP was done on the T91 and SS347 steels for different time periods of 0.5, 1.0, 1.5, 2.0 and 3.0 min. Microstructural modification, increase in surface roughness and enhancement in microhardness up to a depth of 300-350 µm were observed due to USP. There was also increment in surface roughness as well as microhardness with USP time duration. Thermogravimetric analysis of the oxidation tests showed parabolic oxidation kinetics at 650 °C for both the steels. Comparatively more protective oxide scales, containing high amount of Cr, were formed on the USP-treated samples. The thickness of the oxide scale was reduced with increase in the USP time duration. Oxidation resistance of the T91 steel at 650 °C, both in air and steam, was improved by the USP treatment. Oxidation resistance of the SS347 steel at 650 °C was also improved for the USP2.0 and the USP3.0 conditions.

Corrosion behaviour of NiCrFeAl-hBN seal coatings in oxidation environments at a high temperature

The purpose of this investigation was to evaluate the microstructure, high-temperature oxidation behaviour, and hardness of a seal coating under controlled exposures at 750 °C with different exposure times. The results reveal that the main phases in the coating are Ni, FeNi3, and hexagonal BN, with α-Al2O3 peaks appearing after 2-h oxidation. As the exposure time increases, the diffraction peak intensity of α-Al2O3 begins to decrease and Cr2O3 peaks appear after 200 h. After 1000 h, Cr2O3 becomes dominant with only small amounts of α-Al2O3 remaining. The high-temperature oxidation process of the coating includes three stages: the fast stage, transition stage, and slow stage. The oxidation rate is constant in each stage, and in the fast stage and slow stages with values of 7.59 × 10−4 and 8.37 × 10−5 mg2·cm−4·s−1, respectively. Initially, α-Al2O3 forms near the pores in the coating, followed by the formation of Cr2O3. As the exposure time increases, oxidation penetrates into the interior of the coating along phase boundaries to form island-shaped inner oxide layers with high concentrations of Cr, Ni, and Fe. Additionally, hardness increases with increasing oxide percentage.

Influence of microgeometry of iron surface on the oxidation process – A comparison of multiscale geometric methods and their applicability

In this paper, an investigation of the effect of surface roughness on oxidation of polished, ground and sand-blasted samples made of iron exposed at 700 and 750 °C for 2 h in air is reported. Surface roughness was described by the 2D data sets obtained by contact profilometer and derived from microphotographs taken at three different magnifications: 100×, 200× and 500×. Surface roughness and curvature were measured by means of conventional and multiscale analysis. Oxidation behavior was analyzed in terms of mass change and SEM/BSE (scanning electron microscopy/backscattered electrons) observations. The oxidation kinetics was found to be influenced by initial surface roughness, however, its effect was different at 700 °C and 750 °C as the contribution of surface diffusion is greater at the lower temperature. It was also concluded that multiscale analysis can be successfully applied in describing surface roughness prior to high-temperature oxidation processes. The most adequate results were obtained from the data derived by contact profilometer and from microphotographs taken at the highest magnification.

Kinetic modeling of high-temperature oxidation of pure Mg

Abstract A variety of experimental tracer diffusivities of Mg and O in magnesium oxide available in the literature were first assessed. Atomic mobilities including bulk and short-circuit diffusion of Mg and O were then obtained by means of the CALPHAD (Calculation of Phase Diagram) approach. Afterwards, the diffusion-controlled kinetic model of oxidation in a gas-MgO-Mg environment was developed based on the moving boundary model and Fick's law, coupling with the modified thermodynamic description of MgO. A mathematical expression for parabolic rate constant kp of the oxide scale was derived for magnesia and correlated with the thermodynamic and diffusion kinetic information. The evaluated kp results were in line with the experimental data. Finally, the oxidation process of pure magnesium at 673 K was model-predicted, and the predicted evolution of the oxide thicknesses agreed very well with the experimental data. It was indicated that the grain boundaries diffusion of magnesium cations predominated the high temperature oxidation process.

Chemo-mechanical coupling effect on bidirectional diffusion process during oxidation

The chemo-mechanical coupling effect has been widely investigated due to its important impact on many areas, such as Li-ion batteries, biomechanical engineering, hydrogen embrittlement, etc. Meanwhile, the chemo-mechanical coupling effect on the high temperature oxidation process is drawing increasing attention. During oxidation, stress can be induced in the oxide film and will in turn influence the diffusion process and oxidation kinetics. Understanding the coupling effect between stress and oxidation helps to illuminate the mechanism of material degradation and failure. In this work, a concise physical model is developed for oxidation kinetics at elevated temperatures considering the diffusion-stress coupling effect, where both the inward and outward diffusion are considered. The model prediction shows an excellent agreement with the experimental observation. Based on this physical model, we also proposed a parameter to characterize the effects of cation/anion diffusion as well as a phase diagram to describe the universal diffusion–oxidation growth process.