Superior Oxidation Resistance Research Articles

Effect of Laser Scan Speed on Defects and Texture Development of Pure Chromium Metal Fabricated via Powder Bed Fusion-Laser Beam

Chromium (Cr) metal has garnered significant attention in alloy systems owing to its exceptional properties, such as a high melting point, low density, and superior oxidation and corrosion resistance. However, its processing capabilities are hindered by its high ductile–brittle transition temperature (DBTT). Recently, powder bed fusion-laser beam for metals (PBF-LB/M) has emerged as a promising technique, offering the fabrication of net shapes and precise control over crystallographic texture. Nevertheless, research investigating the mechanism underlying crystallographic texture development in pure Cr via PBF-LB/M still needs to be conducted. This study explored the impact of scan speed on relative density and crystallographic texture. At the optimal scan speed, an increase in grain size attributed to epitaxial growth was observed, resulting in the formation of a <100> cubic texture. Consequently, a reduction in high-angle grain boundaries (HAGB) was achieved, suppressing defects such as cracks and enhancing relative density up to 98.1%. Furthermore, with increasing densification, Vickers hardness also exhibited a corresponding increase. These findings underscore the efficacy of PBF-LB/M for processing metals with high DBTT properties.

Superior oxidation resistance of a Y-Hf co-doped Al18Co30Cr10Fe10Ni32 eutectic high-entropy alloy at 1100–1300 °C

We report a study on the oxidation behavior of Al18Co30Cr10Fe10Ni32 eutectic high-entropy alloy co-doped with reactive elements (RE) Y and Hf at 1100–1300 °C. The highly stable eutectic microstructure of γ’/β phases within this alloy contributes to a low coefficient of thermal expansion, thus a low residual stress in the Al2O3 scale. The spinel with a low thickness is formed at the top of Al2O3 scale at 1100 °C due to the low Al diffusion coefficient of γ’-phase and low aspect ratio of β-phase in maze-like eutectic region. As the oxidation temperature increases, the oxidation products transition to exclusive Al2O3 at 1200 °C and 1300 °C, facilitated by the increased Al diffusion coefficient. The Al2O3 scale exhibits a dominated columnar grain microstructure at 1100–1300 °C, suggesting that the inward O diffusion plays more critical role than Al diffusion and thus leads to the low oxidation rate. Besides, the segregation of S to scale/metal interface is inhibited by the uniform RE distribution in the alloy resulting from the fine eutectic microstructure in the alloy. Overall, this alloy exhibits low residual stress in the oxide scale, slow oxidation rate, and the lack of interfacial sulfur segregation, thus contributing to its superior oxidation resistance. The strong oxidation resistance of Y-Hf co-doped Al18Co30Cr10Fe10Ni32 eutectic high-entropy alloy makes it a potential candidate for advanced oxidation-resistant alloy or coating applications.

Vertically interconnected structure enhances the thermal management capability of copper-based composites

Efficient thermal management relies on constructing a network structure. Here, we propose an efficient strategy for fabricating an in-plane vertically interconnected network by integrating copper nanoparticles and nanowires through electrospinning and vertically stacking hot-pressing. This approach offers a dual benefit: creating an in-plane vertically interconnected thermal conductive network while simultaneously protecting the fillers against oxidation. Furthermore, the combination of multi-dimensional hybrid fillers reduces interfacial thermal resistance. Thus, the (Cu NPs-Cu NWs)@PVP/PVA film with hybrid fillers achieves a high thermal conductivity of 22.71 Wm-1K-1, along with superior thermal stability, oxidation resistance, and flexibility, making it promising for advanced electronic device thermal management.

Effect of Fe doped Co–Ni protective coatings on the oxidation behavior and electrical properties of SOFC alloy interconnect materials

In order to enhance the oxidation resistance and electrical properties of interconnects for solid oxide fuel cells (SOFCs), three Co–Ni alloy coatings with varying contents of Fe doping were prepared onto SUS 430 substrate using electroplating method and oxidized in air at 800 °C for 1000 h. The experimental results demonstrated that the alloy coating significantly enhanced both the oxidation resistance and electrical properties of the interconnect substrate. The multi-layer oxidation structure blocked Cr from diffusing outward. Notably, the (Co,Fe)3O4/(Ni,Co)O in the oxidized layer of 5% Fe doped Co–Ni coated steel completely transformed into (Fe,Co,Ni)3O4 spinel layer after long term oxidation, which had the lowest activation energy and the strongest ability of restricting oxygen diffusion inward. Thus, the 5% Fe doped Co–Ni coated steel showed superior oxidation resistance (kp = 8.76 × 10−14 g2 cm−4 s−1) and excellent electrical properties (ASR = 13.19 mΩ cm2) following oxidation for 1000 h.

The effect of nitrogen on the isothermal oxidation of substoichiometric zirconium carbide: Microstructural and spectroscopic investigations

The oxidation behavior of hot-pressed sub-stoichiometric zirconium carbide was investigated through isothermal flow-tube furnace experiments at temperatures ranging from 1000 to 1600 °C. Auxiliary gas composition influence on the oxidation of ZrC0.63 was studied by introducing oxygen to substrates held under either pure argon or nitrogen environments. During furnace ramp-up, prior to isothermal oxygen exposure, nitrogen flow was found to infiltrate the substrate resulting in ZrCxNy formation which provided superior oxidation resistance to the as-received ZrC0.63. Ex situ investigation of ceramic-oxide interfacial regions revealed the presence of carbon precipitate in both material sets at treatment temperatures of up to 1400 °C, along with the presence of the ZrCxOy system. At sufficiently high test temperatures, resulting scale formations for the N2/O2 systems were found to be less porous than the Ar/O2 counterparts, with a higher degree of c-/t-ZrO2 crystallites present at room temperature attributed to nitrogen incorporation into the anion sublattice of ZrO2.

Effect of Pt on Stress Rupture Properties of Pt-Modified Nickel Aluminide Coatings at 1100 °C.

Platinum plays a crucial role in the superior high-temperature oxidation resistance of Pt-modified nickel aluminide (PtAl) coatings. However, PtAl coatings usually serve in thermo-mechanical coupling environments. To investigate whether Pt contributes to the high-temperature mechanical properties of PtAl coating, stress rupture tests under 1100 °C/100 MPa were performed on PtAl coatings with varying Pt contents. The different coatings were obtained by changing the thickness of the electroplated Pt layer, followed by a diffusion heat treatment and the aluminizing process in the present work. The results of the stress rupture tests indicated that an increasing Pt content resulted in a significant decrease in the stress rupture life of PtAl-coated superalloys under 1100 °C/100 MPa. Theoretical calculations and microstructural analysis suggested that an increased coating thickness due to the Pt content is not the main reason for this decline. It was found that the cracks generated close to the substrate in high-Pt-coated superalloys accelerated the fracture failure.

High-purity rayon-based carbon fiber felt prepared by halogen gas purification for superior thermal insulation and oxidation resistance

High-purity rayon-based carbon fiber (CFRay) felt holds significant promise for applications in thermal protection systems and semiconductor crystal growth furnaces. This study employs halogen gas purification and high-temperature purification techniques in the fabrication of high-purity CFRay felt. Additionally, the influence of the purification process on the thermal insulation and oxidation resistance of CFRay felt is investigated. The glow discharge mass spectrometer analysis reveals that purification at a lower temperature of 2300 °C achieves a purity level of 6.9 ppm, surpassing both purified CFRay felt without halogen at 2300 °C (56.1 ppm) and high-temperature treated CFRay felt at 3000 °C (10.4 ppm). Thermal insulation and dynamic-static oxidation resistance tests show that the properties of CFRay felt are concurrently affected by the heat treatment temperature. Compared to high-temperature purification, halogen gas purification operates at lower temperatures, preventing the graphitization of CFRay, thereby ensuring high purity while enhancing thermal insulation and demonstrating relatively superior oxidation resistance. This study offers novel insights into the preparation and performance adjustment of high-purity CFRay felt.

Revealing the superior oxidation resistance of alloy 690 in deaerated supercritical water at 600 °C through advanced characterization

The corrosion behavior of a well-polished Alloy 690 in deaerated supercritical water at 600 °C was examined. The study found that the weight gain follows a near-cubic rate law. A key observation was that the direct external oxidation and the rapid transition from internal to external oxidation within the initial 24-h exposure are responsible for its superior oxidation resistance. As exposure time increases, the transformation of Cr-rich spinel oxides and Ni-rich networks in the internal oxidation zone into Cr2O3 leads to the expansion of the protective chromia layer, effectively slowing down the oxidation process. Conversely, the Cr2O3 layer at the grain boundaries (GBs) was less effective at preventing oxidation, resulting in a significantly faster oxidation rate in these areas compared to the bulk grains. The extensive GB oxidation exhibits little consequential correlation with carbides.

Oxidation behavior of AlCoCrFeNi bond coating in the YSZ-TBCs produced by APS and PS-PVD method

This study prepared the 7YSZ ceramic coatings based on AlCoCrFeNi bond coating by APS and PS-PVD methods, respectively. Two AlCoCrFeNi/7YSZ thermal barrier coating systems with different microstructures of ceramic coatings were obtained, and oxidation experiments at 1000 °C and 1100 °C were carried out for the two thermal barrier coating systems. The results showed that the AlCoCrFeNi/7YSZ(PS-PVD) thermal barrier coating system exhibits superior oxidation resistance compared to the AlCoCrFeNi/7YSZ(APS) thermal barrier coating system at 1000 °C and 1100 °C, which was attributed to the ceramic coating with a unique feather-columnar structure prepared by PS-PVD. Both thermal barrier coatings in this study produced a continuous and dense TGO layer composed of Al2O3 after oxidation experiments. The oxidation rate constants kp of this study's two thermal barrier coatings were lower than the selected MCrAlY/YSZ thermal barrier coating systems under the same experimental conditions. It indicates that the AlCoCrFeNi bond coating exhibited excellent oxidation resistance and possesses the potential to be a new type of bond coating material.

Microstructures and Antioxidation of W Self-Passivating Alloys: Synergistic Effect of Yttrium and Milling Time

Tungsten and its alloys are widely recognized as key components in high-temperature environments. In this study, self-passivating W-Si-xY alloys with varying Y content were prepared using mechanical alloying (MA) and spark plasma sintering (SPS). The synergistic effects of Y content and milling time on the microstructures and oxidation resistance of the alloys were revealed. This study found that the oxidation resistance of the alloys increased as the Y content increased. However, the effect of milling time on oxidation resistance was complex. For W-Si-xY alloys with low Y content (0Y and 2Y), the oxidation resistance decreased with increasing milling time. In contrast, for W-Si-xY alloys with high Y content (4Y and 6Y), the oxidation resistance increased with increasing milling time. This enhanced oxidation resistance is due to the microstructural changes in the protective composite layer, including the size and distribution of W5Si3, Y2Si2O7 aggregates, and W-Y-O melt. The thickness of the oxide layer on the W-Si-6Y alloy after being oxidized at 1000 °C for 2 h was only 70.7 μm, demonstrating its superior oxidation resistance.

Ultrafast synthesis of high-entropy carbides up to 3,273 K for superior oxidation resistance

Ultrafast synthesis of high-entropy carbides up to 3,273 K for superior oxidation resistance

Improved oxidation resistance while maintaining slag corrosion resistance of MgO–SiC–C refractories with moderate amounts of liquid phase

AbstractMgO–SiC–C refractories with superior hot strength, oxidation resistance and slag resistance have potential to become substitute refractories for matte smelting furnace. In the present work, the influence of glass powder addition on phase compositions, hot strength, oxidation resistance, and slag resistance of MgO–SiC–C refractories was investigated. The liquid phase introduced by glass powder filled the pores, blocking the channel for the ingress of the oxygen and thus improving the oxidation resistance. Although the oxidation resistance of such refractories was improved with 1–3 wt% glass powder addition, their hot strength and slag corrosion resistance decreased when the glass powder content was 2–3 wt%. To balance the mechanical properties, oxidation resistance and slag resistance, low amount glass powder addition (1 wt%) was considered better choice.

A ZrB2-SiC(Al) coating with improved oxidation resistance for C/C composites: Design, experimental verification and oxidation mechanism

In order to improve the oxidation resistance of ZrB2-SiC coating, Al2O3 dopant was introduced to modify the structure of oxygen-inhibiting glassy layer. Al2O3-doped ZrB2-SiC (ZrB2-SiC(Al)) coating was designed, optimized and prepared by spark plasma sintering. Microstructure evolution and oxidation mechanism were investigated by experiment and first-principles calculation. Compared with ZrB2-SiC coating, ZrB2-SiC(Al) coating showed a significantly improved oxidation resistance. Characterization and calculation results indicated that the superior oxidation resistance could be ascribed to the higher bridging oxygen content, the improved stability of glass structure, and the decreased oxygen diffusion rate of glassy layer due to the increased solubility of ZrO2.

Microstructure and anti-oxidation behavior of laser clad Ni[sbnd]Si coating on molybdenum surface

Ni-Si alloy coatings with various compositions were fabricated on molybdenum surfaces using laser cladding technology. The sound metallurgical bond without cracks and pores between coatings and substrat was revealed.The microstructure and phase composition of the coatings were analyzed using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The oxidation resistance of the coatings was investigated in a static air environment at 700 °C. The results reveal that the coatings primarily consist of a γ-Ni solid solution, Ni3Si phase, and Mo2Ni3Si phase. Furthermore, the Mo2Ni3Si phase content increases with decreasing Ni content in the powder ratio. The oxidation kinetics curve of the NiSi alloy coatings follows a parabolic law. The oxide layer formed on the coating surface is uniform and dense, comprising SiO2, MoO3, and NiMoO4. Based on the comprehensive analysis of the microstructure of the oxide layer, the Ni90Si10 coating demonstrated superior oxidation resistance

Development of a low-density Co-Ni-Al-Ta-Cr superalloy with high mechanical performance and superior oxidation resistance

In this study, a Co-30Ni-10Al-6Ta-10Cr alloy was designed based on CALPHAD (Calculation of Phase Diagrams) method targeting high γ′ phase fraction and solvus, and optimal thermal processing window. Experimental results concurred with the calculations and validated Cr as a γ phase-forming element in Co-Ni-Al-Ta-based alloys. The incorporation of Cr in the alloy helps mitigate lattice misfit, coarsening rate, and alloy density, while enhancing microstructural stability. A certain amount of Cr led to the development of a superalloy with both high mechanical performance γ′ solvus and low density. Moreover, the oxidation resistance of the Co-Ni-Al-Ta-based high-temperature alloy can be substantially elevated by the introduction of Cr. At 1000 °C, the Co-30Ni-10Al-6Ta-10Cr alloy displayed comparatively low oxidation weight gain, which signifies its excellent oxidation resistance. This is mainly attributed to the formation of continuous (Co,Ni)(Al,Cr)2O4 spinel oxide layers during prolonged oxidation.

High-Temperature Oxidation Resistance and Molten Salt Corrosion Study of YSZ, CeYSZ, and YSZ/CeYSZ Thermal Barrier Coatings by Atmospheric Plasma Spraying

Five thermal barrier coatings (TBCs), namely TBC-1 (YSZ), TBC-2 (CeYSZ), TBC-3 (YSZ:CeYSZ = 1:2), TBC-4 (YSZ:CeYSZ = 1:1), and TBC-5 (YSZ:CeYSZ = 2:1), were fabricated using the atmospheric plasma spraying (APS) method. Their oxidation behaviors at 1100 °C and corrosion resistance to molten salts (V2O5 + Na2SO4) at 900 °C were examined. After 100 h of oxidation, the thermally grown oxide layer (TGO) for YSZ primarily contained Cr and Ni oxides with significant internal fractures, presenting a continuous band-like Al2O3. In dual-ceramic configurations, an increase in CeYSZ thickness led to a rise in Al content and reduced Cr and Ni in TGO, with the surface fracture morphing into an internal porosity. Following salt corrosion, YSZ revealed rod-like YVO4 and m-ZrO2 as corrosion products, whereas CeYSZ displayed chain-structured CeO2, CeYO4, and YVO4 combined with m-ZrO2. YSZ coatings underwent notable phase transitions with evident densification, forming a corrosion layer of approximately 10 μm. Conversely, CeYSZ showed a limited phase change, retaining porosity without a distinguishable corrosion layer. As CeYSZ thickness increased from 100 μm to 200 μm in the dual-ceramic structure, salt penetration reduced. Evidently, the dense structure of CeYSZ heightened diffusion resistance against oxygen and corrosive salts, rendering superior oxidation and corrosion resistance over YSZ. By optimizing the thickness ratio between CeYSZ and YSZ, whilst retaining total ceramic layer thickness, the dual-ceramic TBC’s resistance to high-temperature oxidation and corrosion can be enhanced.

Structural control of nanoporous frameworks consisting of minimally stacked graphene walls

This mini-review provides an in-depth analysis of the formation and post-processing of nanoporous graphene materials via methane chemical vapor deposition (CH4-CVD) using nanostructured metal oxide templates, including Al2O3, MgO, and SiO2. Initially, the formation of graphene sheets is discussed in terms of the role of CH4-CVD, the influence of templates, and the underlying mechanism for tailoring the structures of the graphene-based materials. Following this, the discussion extends to the post-graphene formation process. We focus on key steps, including template removal and graphene repair via zipping reactions at high temperatures. Additionally, we evaluate the conditions to prevent undesired structural transformations. The correlation between the structural features and transformations occurring during post-processing is also examined. The materials fabricated through these methods exhibit impressive properties of high porosity, minimal edge sites, superior oxidation resistance, and elasticity, positioning them as promising materials in various applications.

Atomic Scale Insight into the Oxidation Mechanism of Nb/Ta‐Doped Ti3SiC2/Al2O3 Ceramics

The low oxidation resistance of Ti3SiC2/Al2O3 composites limits their applications as high‐temperature structural materials. To improve the oxidation resistance, Nb and Ta are introduced into the substrate herein. The Nb/Ta‐doped Ti3SiC2/Al2O3 composite shows superior oxidation resistance than clean Ti3SiC2/Al2O3 following the oxidation process at 800–1000 °C for 100 h. The oxidation mechanism is determined via first‐principles calculations. The oxidation process of the composite is controlled by the inward diffusion of O and outward diffusion of Ti. When Nb/Ta elements are doped, their larger atomic radii and stronger binding produce a higher diffusion barrier for O and Ti atoms, which prevents element migration and reduces the thickness of the oxidation layers.

Silver nanowires/cellulose flexible transparent conductive films for electromagnetic interference shielding and electrothermal conversion.

Currently, electromagnetic shielding materials need to meet the characteristics of lightweight, high transmittance, and robust conductivity. Silver nanowires (AgNWs) have progressively found applications in recent years owing to their excellent aspect ratio, conductivity, and flexibility. The properties of AgNWs vary with different aspect ratios, and the length and diameter of AgNWs often exert diverse influences on the photoelectric properties of conductive films. In this study, we combined AgNWs with hydroxypropyl methylcellulose (HPMC) and employed a directional stacking arrangement method to apply AgNWs onto the PET substrate, investigating the properties of four distinct aspect ratios of AgNWs (1000, 750, 625, and 531). Ultimately, the prepared four films achieved electromagnetic shielding capabilities ranging from 26.6 dB to 32.8 dB, with a transmittance range of 89.8% to 94.6%, showing excellent electromagnetic shielding properties. Moreover, the prepared films showed an exceedingly low roughness value (RMS = 7.07 nm), remarkable flexibility, and superior oxidation resistance with the facilitation of HPMC. The films also showed exceptional electrothermal conversion prowess, achieving saturation temperature within a mere 8 seconds, thereby displaying a rapid thermal response. Furthermore, when a voltage of 4 V was applied, the temperature of the thin film remained essentially constant for a duration of 2500 seconds, highlighting its admirable thermal stability, which is of great significance for the development of flexible and transparent electromagnetic shielding materials in the future.

Fluorine enables h-BN sheet to resist oxidizing failures in sulfur atmosphere

Corrosion is one of the most common ways in which metal components are damaged, especially under extreme conditions in the presence of sulfide ions. Due to the excellent properties of hexagonal boron nitride (h-BN) sheets, they can provide effective protection for facilities exposed to sulfur-containing atmospheres. In this paper, the thermodynamic and kinetic behavior of oxygen adsorbed on h-BN and defective D-h-BN sheets in a sulfur-containing atmosphere were performed by first-principles calculations. The adsorption energies, densities of state, band structures, differential charge densities and diffusion energy barriers were systematically investigated. The presence of sulfur reduces the diffusion energy barrier of oxygen, which accelerates the oxidative failure of h-BN sheets. Surprisingly, the F-modified h-BN sheet possesses a higher oxygen diffusion energy barrier, which explains its superior oxidation resistance. Therefore, h-BN sheets are a promising candidate as a protective material in sulfur-containing atmospheres.