Oxidation Resistance In Air Research Articles

Superior oxidation resistance in air during hot stamping of a coating-free press-hardened steel achieved by pre-oxidation

Superior oxidation resistance in air during hot stamping of a coating-free press-hardened steel achieved by pre-oxidation

Microstructure evolution and high temperature air oxidation behaviour of thick Cr coatings at 1200°C

The thick Cr coated Zr-4 alloys were prepared by magnetron sputtering deposition and their microstructure evolution and high-temperature air oxidation behaviour were investigated. Oxidation tests showed that the thick Cr coatings can improve the high-temperature air oxidation resistance of Zr-4 alloy even if the α-Zr(O) layer was formed at some regions. The mechanism of high-temperature air oxidation was also discussed in detail, and these experimental results could provide data for establishing a reliable prediction model of this degradation.

Synthesis and reaction mechanism of high injected electron concentration and low work function [Ca24Al28O64]4+:(4e-) by Sol-gel method combined with spark plasma sintering

The high injected electron concentration and low work function C12A7:e- was successfully prepared by the sol-gel method combined with spark plasma sintering(SPS) using calcium nitrate, aluminum nitrate, citric acid, and ethylene glycol as raw materials. By analyzing the morphology of carbon and its role in the reactive synthesis, we reveal the reaction synthesis mechanism of C12A7:e- under the SPS. The analysis shows that C12A7:e- started to be generated at 800 °C. During the SPS reaction sintering process, carbon atoms from citric acid and ethylene glycol were excited by a pulsed current at high temperature, forming the carbon ions C22- and C (gas). Both act as reducing agents and react with the free oxygen ions O2- in the C12A7 cage cavity to form gaseous CO or CO2, enabling electrons to be injected into the cage cavity, thus generating C12A7:e-. Meanwhile, the graphene oxide (GO) formed on the surface of C12A7:e- grain is produced by the precursor of sol-gel synthesis in the high temperature oxidation environment, which will be conducive to improving the stability of C12A7: e- in air and high temperature oxidation resistance.

Evolution of Microstructure During Stress Relieving Heat Treatment of 1S Aluminium

Aluminium and its alloys are extensively used in nuclear research reactors due to its low neutron absorption coefficient, good heat transfer properties, excellent corrosion and oxidation resistance in air and water environment combined with desirable mechanical properties along with considerable radiation stability. The thin walled tubes are normally manufactured through port hole die extrusion route and used in 'O' tempered condition. The thin tubes in 'O' tempered condition are undergone canning operation which may alter the microstructural features to some extent which may affect mechanical properties. The paper describes the extent to which microstructural and subsequently mechanical properties are altered due to the simulated canning process and further requirements of stress relieving heat treatment to restore the microstructural features and mechanical properties. The following studies are carried out with 1S aluminum tube in 'O' tempered state, simulated canning condition and stress relieved at different temperature, - hardness measurement, X ray line profile analysis for dislocation density measurement, tensile properties measurement using ring tensile testing, electron back scattered diffraction (EBSD) analysis for recrystallization fraction determination and changes in texture components. It is found that the canning operation changes dislocation density, micro-strain, coherent domain size which are well reflected in hardness and ring tensile testing. Subsequent stress relieving at 350°C for 2 hrs. leads to improvement of mechanical properties appreciably.

Synergistic enhancement of thermomechanical properties and oxidation resistance in aligned Co-continuous carbon-ceramic hybrid fibers.

Carbon fibers are highly valued for their lightweight characteristics, outstanding mechanical properties, and cost-efficiency. However, their limited oxidation resistance and low thermomechanical stability in hot air impose constraints on their utilization. Here, we present an approach to simultaneously achieve high thermomechanical properties and high-temperature oxidation resistance in carbon-ceramic hybrid fibers featuring a highly aligned co-continuous topological structure through a continuous process. These hybrid fibers exhibit superior mechanical properties compared to pure carbon fibers with the same diameter (20 μm), including a tensile strength of 2.0 ± 0.2 GPa, Young's modulus of 175 ± 34 GPa, and elongation at break of 1.3 ± 0.2%. Moreover, when subjected to thermal exposure under stress loading conditions in air, the ceramic constituents form a protective oxidized ceramic layer that effectively mitigates thermal oxidation and mechanical loading effects at elevated temperatures, surpassing the performance of carbon fibers. Our discovery offers a promising avenue for bridging the performance gap between cost-effective high-strength carbon fibers and expensive SiC counterparts with exceptional oxidation resistance, which can be applied in many fields wherever high thermomechanical loading and oxidation-resistant properties are important.

High-Temperature Oxidation Behavior of FeCoCrNi+(Cu/Al)-Based High-Entropy Alloys in Humid Air

Previous studies showed some transition metal high-entropy alloy (HEA) compositions can have good oxidation resistance in air up to 800 °C. Four equiatomic HEAs have been developed based on FeCoCrNi with additions of Mn, Cu, Al or Al+Cu. The oxidation behavior of these HEAs was compared in humid (10 vol.% H2O) air at 800 °C for 100–500 h to investigate the influence of water vapor on the oxidation mechanisms. The Cu- and Al-containing alloys exhibited improved oxidation resistance over the Mn composition. For the Cu-containing alloy, a local attack of the Cu-rich phase was observed, which formed an Fe/Ni/Co/Cr spinel that was surrounded by Cr2O3. This oxide was thicker for the humid air atmosphere when compared to dry air, and the transition of the Cu oxide to the spinel was accelerated. The Al-containing HEA formed a thin Al2O3 scale with humidity suppressing AlN formation and forming a smoother oxide layer. The Al+Cu composition had the highest overall oxidation resistance (minimal local attack, no nitridation) and also showed a smooth oxide scale topography under humid air oxidation as opposed to a plate-like, rougher scale under dry air.

Oxidation performance and limitations of additively manufactured SiC/Si─O─C composites at elevated temperatures

AbstractSiC preforms were infiltrated with polycarbosiloxane preceramic polymer to create low‐cost SiC—SixOyCz matrix composites for possible high temperature application. The effect of specimen annealing conditions on the steam and air oxidation resistance was analyzed. Air exposures from 900–1500°C showed stability of the SixOyCz matrix phase with moderate oxidation resistance. After 900°C exposures, oxidation of the composite is primarily limited to the matrix phase, and only at 1200 and 1500°C was SiC consumption visualized. Steam cycle exposures at 1200°C resulted in rapid linear oxidation of the composites with induced specimen swelling from volume expansion associated with internal oxidation. Specimens annealed in argon were found to be the most oxidation resistant due to increased matrix crystallinity and carbon retention. The results of this work were used to develop clear strategies for improving the high‐temperature properties of SiC—SixOyCz composites.

Impact of the reduction of graphite content in critical properties of MgO–C bricks for steelmaking industry

Nowadays, the use of lower amounts of graphite in MgO–C bricks for the steelmaking industry is motivated by several reasons, including the reduction of CO2 emissions. In this work, a MgO–C brick with 12 wt% graphite, was evaluated in comparison with a similar material containing just 8 wt% of this component. The changes induced in the brick by thermal treatments (graphite bed) between 500 and 1400 °C were analyzed comparatively. Moreover, the effect of reducing the graphite content in the mechanical properties at RT, 1000 and 1400 °C (compressive tests, in argon) and the oxidation resistance in air at 1000 and 1400 °C was determined. At 1000 °C, the refractory with 8 wt% graphite exhibited the highest mechanical strength and stiffness. Furthermore, although the decarburized area was larger after treatment at 1000 °C in air in this brick, the mass and carbon losses showed the opposite trend.

Effect of Si content on the oxidation behavior of CoCrWSi coatings at 900 °C

In this study, CoCrWSi coatings with different Si contents were prepared via high-velocity oxygen fuel spraying, and the effect of Si content on their high-temperature oxidation resistance in air was studied at 900 °C. The microstructures and chemical compositions of oxide scales were characterized through scanning electron microscopy, electron probe microanalysis, and X-ray diffraction. The results revealed that the oxidation resistance of the produced CoCrWSi coatings gradually increased with increasing Si content. Moreover, the beneficial effects of Si content on the oxidation resistance were discussed in terms of Si depletion. The addition of Si prevented the outward diffusion of Cr atoms, and inhibited internal oxidation, while the depth of internal oxidation varied significantly with the oxidation time.

Improved Oxidation Resistance of Graphite Block by Introducing Curing Process of Phenolic Resin.

The purpose of this study is to improve the oxidation resistance of graphite blocks after graphitization at 2800 °C by introducing a curing process of phenolic resin, used as a binder to control the pore size. Using the methylene index obtained from FTIR, the curing temperature was set to 150 °C, the temperature at which cross-linking most highly occurs. Graphite blocks that had undergone curing, and were carbonized with a slow heating rate, showed increased mechanical and electrical properties. Microstructural observation confirmed that the curing process inhibited the formation of large pores in the graphite block. Therefore, the cured graphite block showed better oxidation resistance in air than a non-cured graphite block. Oxidation of the graphite block was caused by pores created by pyrolysis of the phenolic resin binder, which acted as active sites.

Effect of YSZ/TaSi2-MCrAlY thermal barrier coatings on oxidation resistance in air and water vapor

Effect of YSZ/TaSi2-MCrAlY thermal barrier coatings on oxidation resistance in air and water vapor

Study on oxidation resistance and Al diffusion of Cr1-xAlx coatings with different low Al content

Cr1-xAlx coatings with different low Al content were prepared on Zr alloy by magnetron sputtering. The influence of Al content on the microstructure, adhesion strengths, and oxidation resistance of the Cr1-xAlx coating was systematically evaluated. Air oxidation results show that a Cr91.4Al8.6 coating shows better air oxidation resistance. After steam oxidation tests, a Cr2O3-rich and Al2O3-rich double oxide layer is found to be formed in the Cr91.4Al8.6 coating. The Al2O3-rich layer can effectively prevent the surface Cr2O3 layer from being consumed by Zr diffusion along the Cr grain boundary and maintain stable double oxide structure. Moreover, the diffusion mechanism for the Al element during steam oxidation of the Cr91.4Al8.6 coating was analyzed in detail.

Microstructure and Oxidation Behavior of a CrMoNbTaW Refractory High Entropy Alloy

This work reports on the microstructure and oxidation behavior of a refractory CrMoNbTaW high entropy alloy (HEA) produced by vacuum arc melting. Microstructure and mechanical properties of both the as-synthesized alloy and that annealed in air for 6 h in the temperature range 600–900 °C were evaluated in detail. The phase identification and microstructure analyses were performed using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) while microhardness was measured using Vickers hardness tests. The as-fabricated alloy consists of a multiphase microstructure consisting of three phases: a W-rich phase, a Mo-rich phase, and a solid solution phase of BCC structure. As-synthesized HEA for this composition demonstrates excellent microhardness values, of 787 ± 83.6 HV, which was retained after annealing. The oxidation resistance in air was evaluated from 600 to 1400 °C for both 12 and 24 h of exposure time. The alloy exhibits a parabolic mass gain until 1100 °C, for which it begins to exhibit a decreasing mass gain at 1200 °C and, subsequently, a mass loss at 1300 and 1400 °C. The surface oxidation products were investigated, for which no protective oxides were identified. The surface oxide scale consisted of Cr, Nb, Ta, and trace amounts of W. The Mo content at the surface decreased as temperature increased, with no Mo content identified after 1100 °C.

Influence of Al/(Al+Cr) ratio and doping effects on wear and molten aluminum attack resistance in AlCrN-based PVD coatings for lube-free aluminum die casting

AlCrN-type PVD coatings are excellent candidates for die coatings; they reduce or eliminate the need for conventional lubricants in aluminum die casting. A variety of AlCrN-based coatings are commercially available, and an understanding of their differences is needed to ensure optimum performance in the die casting process. In this work, the effects of Al/(Al+Cr) ratio, TiCN-doped layers, surface roughness, and coating defect population were evaluated for five AlCrN-based PVD coatings. Characterization was performed to determine the structure, microstructure, roughness, nature and distribution of surface defects and coating adhesion to the substrate. Also, tests were conducted to evaluate wear, oxidation, and resistance to molten aluminum attack. In the modified molten aluminum test, coatings with higher roughness and higher fractions of microparticles displayed greater adhesion to the solidified aluminum. As-deposited coatings with higher Al/(Al+Cr) ratio provided better protection (little or no adhesion) when in contact with the molten aluminum, but the protection decreased when post deposition polishing was applied to the coating, where some aluminum reaction was observed even without measurable adhesion. Combining the AlCrN coating with alternating nanolayers of TiCN not only provided higher protection to molten aluminum attack compared with the higher Al/(Al+Cr) ratio coatings, but also promoted the lowest coefficient of friction, smallest wear rate, and a similar air oxidation resistance. Thus, for the five coatings examined, the combination of results indicates the multilayer (Al0.34Cr0.11N0.55)0.84/(TiC0.4N0.6)0.16at.% coating is an excellent candidate for industry in-plant trials geared towards moving aluminum die casting towards a lube-free process.

Oxidation resistance of magnesium alloyed by different elements: a brief review

The application of magnesium (Mg) and its alloys in automotive and aerospace industry is promoted gradually because of its outstanding properties, such as light weight, high specific strength and excellent castability. However, as a chemically active metal, Mg and its alloys generally possess low oxidation resistance in air at high temperatures because of the high affinity of Mg for O. This has caused a lot of industrial waste and a short service life. In the present work, according to the relevant mechanism of Mg alloy oxidation in air at high temperature, the effect of alloying elements on the oxidation of pure Mg and Mg alloys as well as the research progress of oxidation resistant Mg alloys are briefly reviewed.

OUTOKUMPU MODA 409/4512

Abstract Outokumpu Moda 409/4512 is a weldable, titanium-stabilized 11.5% chromium ferritic stainless steel with good oxidation resistance in dry air. Because of its titanium alloying, Outokumpu Moda 409/4512 can be welded in all dimensions without becoming susceptible to intergranular corrosion. It is possible to use Outokumpu Moda 409/4512 at elevated temperatures, for example in automotive exhaust systems, where it is often used to replace aluminum-coated carbon steel. This datasheet provides information on composition, physical properties, elasticity, and tensile properties. It also includes information on corrosion resistance as well as casting, heat treating, machining, and joining. Filing Code: SS-1342. Producer or source: Outokumpu Oyj.

Effect of alloying element on microstructure, mechanical property, and oxidation resistance of Zr─Me─C (Me═Si/Y) coatings

AbstractAccident‐tolerant fuels (ATFs) are proposed to provide improved safety response to a loss of coolant accident (LOCA) scenario while maintaining good operational characteristics under normal conditions. In this work, Zr─Me─C (Me═Si or Y) was proposed as candidate coatings for ATF applications. The influence of Si and Y with varied concentration on microstructural evolution, mechanical property, and oxidation resistance of Zr─Me─C coatings were investigated. Based on combined results of X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, and X‐ray photoelectron spectroscopy, it was found that Si or Y doped ZrC0.55 coatings presented tunable composition and microstructure. Improved air oxidation and spallation resistance were achieved with the incorporation of Me atoms, attributing to the formation of SiO2 and ZrSiO4 and/or the stabilization of zirconia. Under a simulated LOCA condition, decreased weight gains of 13.6 at.% Si and 22.5 at.% Y coated Zry‐4 alloys were achieved. nc‐ZrSiC/nc‐ZrSi (13.6 at.% Si) coating exhibited enhanced mechanical property and oxidation resistance in both high‐temperature air and LOCA conditions, which could be regarded as potential candidate for the applications in ATFs.

Effect of pre-oxidation on hot corrosion resistance of HR3C stainless steel in sulfate salt with or without Fe2O3

HR3C steel exhibits high oxidation resistance in air at 700 °C owing to the formation of a dense chromia scale. In the presence of sulfate salt deposition (Na2SO4:K2SO4 = 1:1), hot corrosion occurs. It leads to the dissolution and re-precipitation of Cr2O3 platelets and severe internal corrosion. Pre-oxidation can notably enhance corrosion resistance with almost no internal corrosion zone. When the deposited sulfate salt contains Fe2O3 (Na2SO4:K2SO4:Fe2O3 = 1:1:1), HR3C steel suffers even severer hot corrosion. Its scale spalls off easily and internal corrosion develops deep into the steel. Meanwhile, pre-oxidation played almost no positive effect on corrosion in sulfate salt containing Fe2O3.

Ultra-high-temperature tantalum-hafnium carbonitride ceramics fabricated by combustion synthesis and spark plasma sintering

We report the fabrication of dense single-phase (Ta,Hf)CN carbonitride ceramics using a combination of combustion synthesis (CS) and spark plasma sintering (SPS). The ceramic powder was produced by high-energy ball milling of the reactants (Ta, Hf, C) in different atomic ratios followed by CS of the obtained nanostructured composites in a nitrogen atmosphere. X-ray diffraction analysis of the combustion products revealed the formation of (Ta,Hf)CN with cubic B1 structures as the dominant phases for all investigated compositions. The SPS of the as-synthesized powders allowed both homogenization of the composition and consolidation of the bulk single-phase carbonitride ceramics with a relative density of 98 ± 1 %. Ta25Hf75CN showed the highest hardness (19.4 ± 0.2 GPa) and fracture toughness (5.4 ± 0.4 MPa m1/2) among the investigated composites and excellent oxidation resistance in air.

High Temperature Oxidation Kinetics of Shot-Peened and Laser-Shock Peened Ti-Beta-21S

Isothermal oxidation tests of mechanically treated Ti-Beta-21S (TIMET, Ti–15Mo–3Nb–3Al–2Si, ASTM Grade 21) were performed under dry air at 650, 700 and 750 °C for 100 h and compared to untreated samples. Two different mechanical surface treatments were used: ultrasonic shot-peening (SP) and laser-shock peening (LSP). The study investigates the effect of both treatments on the oxidation kinetics of the process and the role of atmospheric nitrogen insertion. With this aim, oxidation experiments were also performed under pure oxygen. The results show that the oxidation is governed by diffusion after a short transient time. Both SP and LSP treatments improve the high temperature oxidation resistance of Ti-Beta-21S in dry air, but not in pure oxygen. The formation of a nitrogen-enriched layer at the oxide–metal interface, which is promoted by the mechanical surface treatments, explains the increase in the oxidation resistance in air by slowing down the diffusion of oxygen into the metal.