Improved Oxidation Resistance Research Articles

Theoretical investigation on structure, mechanical performance and oxidation resistance of the boron-doped PyC interphase in SiCf/SiC composites

Pyrolytic carbon (PyC) is widely used as the interphase in SiCf/SiC composites because of the crack deflection capability originating from its weakly bonded layered structure. However, the poor oxidation resistance limits its application in SiCf/SiC. Boron doping can improve oxidation resistance due to the crack-healing effects of boron oxide. To explore the optimal boron doping content in PyC interphase, structure characters and mechanical properties of C128−xBx (x = 8, 20, 32, 44, 64) were simulated by ab-initio molecular dynamics. Modeling results suggest a transition of C128−xBx from layered to amorphous accompanied by a change of its elasticity tensor from strongly anisotropic to nearly isotropic. The predicted optimal boron content is near 34 at%, at which the B-doped PyC maintains a layered structure with a high crack deflection potential according to the Cook & Gordon model while having a high crack-healing capability with a large volume expansion factor.

Mass uptake during oxidation of metallic alloys: Literature data collection, analysis, and FAIR sharing

The area-normalized change of mass (Δm/A) with time during the oxidation of metallic alloys is commonly used to assess oxidation resistance. Analyses of such data can also aid in evaluating underlying oxidation mechanisms. We performed an exhaustive literature search and digitized normalized mass change vs. time data for 407 alloys. To maximize the impact of these and future mass uptake data, we developed and published an open, online, computational workflow that fits the data to various models of oxidation kinetics, uses Bayesian statistics for model selection, and makes the raw data and model parameters available via a queryable database. The tool, Refractory Oxidation Database (https://nanohub.org/tools/refoxdb/), uses nanoHUB’s Sim2Ls to make the workflow and data (including metadata) findable, accessible, interoperable, and reusable (FAIR). We find that the models selected by the original authors do not match the most likely one according to the Bayesian information criterion (BIC) in 71% of the cases. Further, in 56% of the cases, the published model was not even in the top 3 models according to the BIC. These numbers were obtained assuming an experimental noise of 2.5% of the mass gain range, a smaller noise leads to more discrepancies. The RefOxDB tool is open access and researchers can add their own raw data (those to be included in future publications, as well as negative results) for analysis and to share their work with the community. Such consistent and systematic analysis of open, community-generated data can significantly accelerate the development of machine-learning models for oxidation behavior and assist in the understanding and improvement of oxidation resistance.

Al2O3 atomic layer deposition on a porous matrix of carbon fibers (FiberForm) for oxidation resistance

Atomic layer deposition (ALD) was used to coat a porous matrix of carbon fibers known as FiberForm with Al2O3 to improve oxidation resistance. Static trimethylaluminum (TMA) and H2O exposures for Al2O3 ALD were used to obtain the uniform coating of this high porosity material. The carbon surfaces were initially functionalized for Al2O3 ALD by exposure to sequential exposures of nitrogen dioxide and TMA. A gravimetric model was developed to predict the mass gain per cycle under conditions when the ALD reactions reached saturation during each reactant exposure. The uniformity of the Al2O3 ALD coating on FiberForm was confirmed by scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS) analysis. The SEM, EDS, and gravimetric models were all consistent with a uniform Al2O3 ALD coating on the porous carbon fiber network when the ALD reactions reached saturation on the entire surface area. In contrast, the profile of the Al2O3 ALD coating on the FiberForm was also characterized using undersaturation conditions when the ALD reactions did not reach saturation throughout the FiberForm sample. Based on comparisons with results from models for ALD in porous substrates, these Al2O3 coverage profiles were consistent with diffusion-limited Al2O3 ALD. Oxidation of the FiberForm and the Al2O3 ALD-coated FiberForm was also investigated by thermogravimetric analysis (TGA). TGA revealed that a 50 nm thick Al2O3 coating deposited using 400 Al2O3 ALD cycles enhanced the oxidation resistance. The Al2O3 ALD coating increased the oxidation onset temperature by ∼200 °C from 500 to 700 °C. The oxidation of the FiberForm removed carbon and left the Al2O3 ALD coating behind as a white “skeleton” that preserved the shape of the original FiberForm sample. The Al2O3 ALD coating also decreased the oxidation rate of the FiberForm by ∼30%. The oxidation rate of the Al2O3 ALD-coated FiberForm samples was constant and independent of the thickness of the Al2O3 ALD coating. This behavior suggested that the oxidation is dependent on the competing O2 diffusion into the FiberForm and CO2 diffusion out of the FiberForm.

High-temperature oxidation behaviour of a Co-based superalloy fabricated through laser powder bed fusion

This study investigated the oxidation behaviour of a Co-based superalloy fabricated through laser powder bed fusion at 900 ℃. In terms of oxidation products, the results revealed the generation of basic oxides, such as CoO, Al2O3 and TiO2, and Co-containing spinels, such as CoAl2O4 and Co2TiO4. Heat treatment improved oxidation resistance by reducing the parabolic oxidation rate constant from 0.17234 to 0.10032 mg2 cm−4 h−1. γ′ precipitates, twin boundaries and less spallation in the heat-treated sample contributed to this improvement, leading to a superior oxidation resistance in this study than in previously reported Co-Al-W-based alloys.

Fulvic Acid Alleviates the Toxicity Induced by Calcium Nitrate Stress by Regulating Antioxidant and Photosynthetic Capacities and Nitrate Accumulation in Chinese Flowering Cabbage Seedlings

Continuous cropping can lead to an excessive accumulation of nitrate in facility-cultured soil. Excessive accumulation of nitrate gradually becomes the main reason for crop failure in vegetables and endangers human health. Therefore, the exploration of effective measures to decrease abundant nitrate accumulation in Chinese flowering cabbage is indispensable. In this study, a kind of plant growth regulator, fulvic acid (FA), was used to study its positive effect on alleviating the growth inhibition induced by excessive Ca(NO3)2 in Chinese flowering cabbage. Meanwhile, we conducted hydroponic cultivation and measured the growth indices, photosynthetic and oxidation-reduction characteristics of Chinese flowering cabbage with different treatments. After determining the optimal treatment concentration, we mainly designed four treatment groups, including Con, FA, Ca(NO3)2 and FA + Ca(NO3)2 cotreatment, to explore the regulatory mechanism by which FA alleviates Ca(NO3)2 stress in Chinese flowering cabbage. The results showed that FA can effectively alleviate the inhibitory effect of excessive Ca(NO3)2 on the growth of Chinese flowering cabbage seedlings. FA recovered the photosynthetic capacity of seedlings under Ca(NO3)2 stress. In addition, FA depressed the accumulation of O2·−, H2O2, malondialdehyde (MDA) and relative electrical conductivity, but increased the activity of antioxidant enzymes, including SOD, POD, CAT and APX, which finally enhanced the stress resistance of Chinese flowering cabbage to Ca(NO3)2. The expression of nitrate-related transporters, BcNRT1.1 and BcNRT1.5, was depressed by FA, which inhibited redundant nitrate absorption and restricted more nitrate from being stored in the roots instead of being transferred to the shoot. Ultimately, nitrate accumulation in the edible part was reduced in Chinese flowering cabbage seedlings. In general, exogenous FA may alleviate nitrate stress by improving oxidation resistance, photosynthetic capacity and redundant Ca(NO3)2 accumulation in Chinese flowering cabbage.

Fabricating a MnCo coating to improve oxidation resistance and electrical conductivity of Crofer22H alloy as SOFC interconnect

The oxidation kinetic behavior of Crofer22H alloy at 700–800 °C was investigated. Due to the high oxidation rate exhibited at 800 °C, the xCr-MnCo dual-structured spinel coating was prepared by magnetron sputtering. The element diffusion behavior of the coating/alloy system was changed by control the formation of Cr layer with different thicknesses on the surface. Appropriately increase the thickness of Cr barrier layer can effectively hinders the Fe outward diffusion and improve the antioxidant performance. Fe doped into Mn–Co spinel increased the electron hopping in the crystal structure. Higher electron hopping and thin Cr2O3 layer reduced the electron resistance.

Improvement of Oxidation Resistance for Ni-Base Single Crystal Superalloy TMS-238 by Suppression of Sb Segregation at Oxide/Substrate Interface Using CaO

Improvement of Oxidation Resistance for Ni-Base Single Crystal Superalloy TMS-238 by Suppression of Sb Segregation at Oxide/Substrate Interface Using CaO

Improved oxidation resistance and infrared emissivity of tantalum disilicide particles with sol-gel derived SiO2 coatings

As an important high-temperature structural material, tantalum disilicide (TaSi2) suffers from performance degradation associated with high temperature oxidation due to the poor oxygen diffusion barring effect of the mixed Ta2O5/SiO2 oxidation scale. In this work, silica coating was prepared on the surface of TaSi2 powder by a sol-gel method. The oxidation resistance was studied by thermogravimetric tests in non-isothermal oxidation and isothermal oxidation, as well as by oxidation treatment in a tube furnace at temperatures ranging from 800 °C to 1400 °C. The spectral emissivity of raw TaSi2, coated TaSi2 and the oxidized ones was compared and analyzed. The amorphous SiO2 coating is composed of numerous nanoparticles and covers most of the surface of TaSi2 particles. The oxidation weight gain of coated TaSi2 during heating from RT to 1200 °C and 1400 °C decreases from 29.8% and 30.9–3.0% and 8.6%, respectively. And the oxidation is controlled by diffusion in the overall process. The coated TaSi2 combines the advantageous radiation property of TaSi2 core and SiO2 coating. Compared with that of raw TaSi2, the emissivity of coated TaSi2 at the wavelength range of 200–2500 nm and 2.5–25 µm has increased by 7.5% and 13.2%, respectively, and the property did not deteriorate after oxidation at 1200 °C, suggesting that the coated TaSi2 is an excellent emitting agent during the entire service life.

Improving oxidation resistance of wire arc additive manufactured Inconel 625 Ni-based superalloy by pack aluminizing

Improving oxidation resistance of wire arc additive manufactured Inconel 625 Ni-based superalloy by pack aluminizing

Low temperature synthesized high entropy carbide composites: A potential high temperature anti-wear material

Bulk Al2O3/(NbTaMoW)C composites with uniform distribution of Al2O3 were designed and fabricated based on thermite reaction. The optimized composites were subjected to mechanical/tribological performance testing and directly compared to (NbTaMoW)C, revealing a significantly enhanced mechanical properties and wear resistance at high temperature. Compared to (NbTaMoW)C, the flexural strength and fracture toughness of Al2O3/(NbTaMoW)C composites significantly enhanced. The measured hardness value is 8% higher than that of (NbTaMoW)C. For the first time, the tribological behavior of Al2O3/(NbTaMoW)C and (NbTaMoW)C was studied systematically at temperatures from 25 °C to 800 °C. Al2O3/(NbTaMoW)C and (NbTaMoW)C present excellent wear resistance below 600 °C, while the wear rate exhibited an obvious increasing at 600 °C–800 °C. The specific wear rate of Al2O3/(NbTaMoW)C is much lower than that of (NbTaMoW)C at 600–800 °C. Al2O3/(NbTaMoW)C exhibits remarkable anti-wear performance at high temperature because the presence of Al2O3 improves oxidation resistance and decreases oxidation wear.

Characterization of NiTiNb10.5 shape memory alloy: microstructural aspects and high-temperature oxidation behavior

The influence of Niobium addition on the high-temperature oxidation behavior of NiTi shape-memory alloys was investigated. Mass-gain kinetics were determined for up to 100 h oxidation at 800, 900 and 1000 °C. Niobium addition drastically reduced the oxidation rates. The surface and cross-section of the resulting oxide layers were characterized by XRD and SEM/EDS. The presence of Nb changed the morphology, phase assemblage, and composition of the scale product, which directly influenced the observed results. The postulated reasons for the improved oxidation resistance were the Nb-doping of TiO2 and the formation of an Nb-rich layer at the scale/alloy interface.

Rutin alleviated lipopolysaccharide-induced damage in goat rumen epithelial cells.

Rutin, also called vitamin P, is a flavonoids from plants. Previous studies have indicated that rutin can alleviate the injury of tissues and cells by inhibiting oxidative stress and ameliorating inflammation. There is no report on the protective effects of rutin on goat rumen epithelial cells (GRECs) at present. Hence, we investigated whether rutin can alleviate lipopolysaccharide (LPS)-induced damage in GRECs. GRECs were cultured in basal medium or basal medium containing 1 μg/mL LPS, or 1 μg/mL LPS and 20 μg/mL rutin. Six replicates were performed for each group. After 3-h culture, the GRECs were harvested to detect the relevant parameters. Rutin significantly enhanced the cell activity (p<0.05) and transepithelial electrical resistance (TEER) (p<0.01) and significantly reduced the apoptosis rate (p<0.05) of LPSinduced GRECs. Rutin significantly increased superoxide dismutase, glutathione peroxidase, and catalase activity (p<0.01) and significantly decreased lactate dehydrogenase activity and reactive oxygen species and malondialdehyde (MDA) levels in LPS-induced GRECs (p<0.01). The mRNA and protein levels of interleukin 6 (IL-6), IL-1β, and C-X-C motif chemokine ligand 8 (CXCL8) and the mRNA level of tumor necrosis factor-α (TNF-α) and chemokine C-C motif ligand 5 (CCL5) were significantly increased in LPS-induced GRECs (p<0.05 or p<0.01), while rutin supplementation significantly decreased the mRNA and protein levels of IL-6, TNF-α, and CXCL8 in LPS-induced GRECs (p<0.05 or p<0.01). The mRNA level of toll-like receptor 2 (TLR2), and the mRNA and protein levels of TLR4 and nuclear factor κB (NF-κB) was significantly improved in LPS-induced GRECs (p<0.05 or p<0.01), whereas rutin supplementation could significantly reduce the mRNA and protein levels of TLR4 (p<0.05 or p<0.01). In addition, rutin had a tendency of decreasing the protein levels of CXCL6, NF-κB, and inhibitor of nuclear factor kappa-B alpha (0.05< p<0.10). Rutin could significantly decreased interferon regulatory factor 3 mRNA expression in LPS-induced GRECs (p<0.05), whereas interferon induced protein with tetratricopeptide repeats 3 (IFIT3) and toll-interacting protein (TOLLIP) mRNA expression was not significantly different between the groups. LPS reduced the tight junction protein zonula occludin 1 (ZO-1) level in GRECs whereas rutin enhanced it. Rutin significantly improved tight junction protein Claudin-1 mRNA expression in LPS-induced GRECs (p<0.01), but could not affect tight junction protein Occludin mRNA expression. Rutin alleviated LPS-induced barrier damage in GRECs by improving oxidation resistance and anti-inflammatory activity, which may be related to TLR/NF-κB signaling pathway inhibition.

Heterogeneous oxidation behavior and kinetic mechanisms of SiBCN ceramic with structure of MA-SiBCN coated by PDCs-SiBCN

In this study, SiBCN ceramics with a structure of three-dimensional PDCs-SBCN network structure coated MA-SiBCN (MA@PDCs-SiBCN) were fabricated, which significantly improved the sintering activity and oxidation performance. The effect of MA@PDCs-SiBCN structure on oxidation behaviors and kinetics of oxide layer growth of the SiBCN ceramics at 1500 ℃ was investigated, indicating that the significantly improved oxidation resistance is attributed to the different heterogeneous oxidation behaviors, especially in the initial stage. Therefore, the heterogeneous oxidation behaviors and kinetic laws of different phases in MA@PDCs-SiBCN ceramics at different temperature ranges and their effects on structural evolution and oxide layer composition were analyzed by comparison with the MA-SiBCN ceramics. The significantly improved oxidation resistance of MA@PDCs-SiBCN ceramics should be attributed to the inhibition of MA@PDCs-SiBCN structure to heterogeneous oxidation, especially the consumption of t-C, and different oxide layer composition generated from microcrystalline structure rather than nanocapsule-like crystalline structure.

Fabrication of flat stainless steel substrates with improved oxidation behavior for metal-supported solid oxide cells using aqueous tape casting

An aqueous tape casting procedure was developed and optimized to fabricate thick, flat tapes for use as porous stainless-steel substrates for metal-supported solid oxide cells (MS-SOCs). Curling tape is one of the main challenges when using aqueous based slurry formation. This work demonstrated that the sedimentation problem can be solved by increasing solid loading rather than adding excessive binder to raise viscosity. The effect of various casting surfaces on tape curling was also investigated. Materials that allow easy tape release resulted in flatter tapes once the water was evaporated. In addition, substrate oxidation resistance at high temperature was evaluated with respect to starting powder size, sintering extent, and pore former types. High sintering extent that removes or encloses the porosity between steel particles while retaining porosity left by pore formers can effectively prevent breakaway oxidation due to local chromium depletion. Carbon residue in the steel substrates from the slurry organic content can be decreased when formulating the slurry to prevent Cr-rich phase formation in the steel, which severely compromises the substrate oxidation resistance and ductility. By dwelling the substrate in high purity hydrogen, the sensitization can be reversed, but more detailed investigation of the reaction dynamics is needed. By combining the strategies described, this work produced crack-free, flat, 400–500 μm thick stainless steel substrates with 28.7 vol% porosity and improved oxidation resistance compared to previous substrates fabricated by dry pressing of fine powders.

Formation of silicon carbide nanowire coatings on C/C composites using an in situ catalytic strategy for improved oxidation resistance

A low-cost in situ catalytic reaction strategy was employed to successfully prepare SiC–Si coatings on the C/C matrix. The addition of catalysts enabled the fabrication of SiC nanowire coatings at lower temperatures. The effect of catalyst amount (Fe(NO3)3·9H2O) and preparation temperature on the interface microstructure and oxidation resistance of SiC–Si coated C/C composites was systematically investigated. Results demonstrated that the nanowires with a addition of Fe(NO3)3–9H2O at 2 wt% showed maximum density and yield. Additionally, it was observed that the oxidation resistance of the coatings exhibited an initial rise followed by a subsequent decline as the sintering temperature increased. The superior oxidation resistance of the coatings obtained at 1300 °C can be attributed to the in-situ formation of a substantial silicon oxide layer on the surface. This layer effectively fills the cracks and pores within the coating. Furthermore, the failure of the coating was mainly attributed to oxygen diffusion through the microcracks and pores.

High‐Temperature Oxidation Behavior of Medium‐Manganese Austenitic Steel

The high‐temperature oxidation behavior of medium‐manganese austenitic steel is investigated. The double‐layered oxide scale is formed in the investigated samples. The outer oxide layer consists of (Fe,Mn)‐rich oxides, while the inner oxide layer is mainly composed of AB2O4 spinel oxides. When the oxidation temperature is 800 °C, a region composed of oxide and ferrite is formed in the substrate surface layer. When the oxidation temperature is 900 and 1000 °C, there is no such region observed in the substrate surface layer. Although the content of Al in the Fe–Mn–Al sample and the content of Si in the Fe–Mn–Si sample are relatively lower than the content of Cr in the Fe–Mn–Cr sample, the oxidation resistance of the Fe–Mn–Al and Fe–Mn–Si samples is still better than that of the Fe–Mn–Cr sample. The oxidation resistance of the Fe–Mn–Cr–Al and Fe–Mn–Cr–Si samples is also better than that of the Fe–Mn–Cr sample. The addition of Al and Si can improve the oxidation resistance of the Fe–Mn–Cr sample. Besides, the oxidation resistance improvement effect of adding Si to the Fe–Mn–Cr sample is better than that of adding Al to the Fe–Mn–Cr sample.

Oxidation resistance and mechanical properties of AlTiZrHfTa(-N) high entropy films deposited by reactive magnetron sputtering

(AlTiZrHfTa)1−xNx refractory high entropy films (RHEFs) were deposited by direct current magnetron sputtering in various nitrogen ratios (RN2 = N2/(Ar+N2)) on flat glass, silicon and sapphire substrates. The nitrogen-free film is amorphous while the nitrides are single-phased solid solutions with Face-Centered Cubic (FCC) structures. The hardness increases from 6.4 GPa for the nitrogen-free film to 25.3 GPa for the film obtained at RN2 = 20%. A preferred orientation from (111) to (200) occurs when RN2 increases from 5% to 50%. H/E and H3/H2 reports show high values for the film deposited at RN2 = 20% compared to that at 10%. However, this latter has the best compromise in terms of mechanical properties related to a lower residual stress value. The nitrides films obtained with RN2 ≥ 5%, are thermally stable at 800 °C for 3 h under vacuum. Compared to the metallic film they show an improved oxidation resistance. In fact, the Kp constant of the nitride (RN2=20%) is lower (1.22 10−7 g2 cm−4 h−1) than that of the nitrogen-free film (1.77 10−6 g2 cm−4 h−1). The corresponding activation energies (Ea) are respectively calculated at 94.8 KJ. mol−1 and 45.5 KJ.mol−1. After oxidation process, TEM analysis reveal the formation of homogeneous mixed oxide.

Chromium Diffusion Coatings for Mo-Based Silicides to Improve Their Oxidation Resistance

The oxidation behavior of two ternary Mo-Si-Ti alloys (eutectic Mo-20.0Si-52.8Ti and eutectoid Mo-21.0Si-34.0Ti) was investigated using thermogravimetric analysis at 700 °C, 900 °C, and 1300 °C for 100 h. The eutectic alloy formed a protective SiO2/TiO2 oxide scale, whereas the eutectoid alloy showed catastrophic oxidation. To improve the oxidation behavior of these alloys, chromium diffusion coatings deposited via pack cementation on the surface were investigated. Cr coatings were found to be suitable for improving oxidation resistance at 700 °C and 900 °C but failed at 1300 °C due to the evaporation of thin scales. At 700 °C and 900 °C, the formation of a Cr2O3 scale was proven on the Ti-rich/Mo-lean eutectic composition. After exposure, the Ti-lean/Mo-rich eutectoid composition, which is intrinsically more prone to oxidation, was found to form a continuous Cr2O3 scale only at 700 °C.

Effect of the anti-seepage masking layer on the microstructure evolution of Ni-based superalloy during co-deposition of the Al-Si coating

This study optimizes turbine blade microstructures during production, specifically focusing on surface treatments for blade airfoils and dovetails. Blade airfoils need to prepare the Al-Si coating to improve oxidation resistance, while blade dovetails must prepare the anti-seepage masking layer to hinder the deposition and diffusion of active atoms into the substrate. The effect of the anti-seepage masking layer on the microstructure evolution of IN718 superalloys during co-deposition of the Al-Si coating was systematically revealed. Results indicate that by adding Si elements to modify the aluminide coating, a uniform and dense Al-Si coating was prepared on IN718 superalloys at 950 ℃ for blade airfoils, enhancing oxidation resistance. Meanwhile, the anti-seepage masking layer with 42 µm could effectively prevent the deposition and diffusion of Al and Si atoms into the substrate for blade dovetails. Defects such as interface layers, micro-voids, and cracks between the masking layer and substrate facilitate the removal of the anti-seepage masking layer from the substrate after heat treatment. On the contrary, the thicker anti-seepage masking layer will induce the upward diffusion of Cr and Mo atoms and form a stronger metallurgical bonding with the substrate, which is difficult to remove and will harm the properties of the substrate.

Tribological study at high temperature of the c-TiAlON oxynitride coating deposited by cathodic arc on H13 tool steel

Coatings were deposited on AISI-H13 steel by cathodic arc Physical Vapor deposition (arc-PVD). Grazing Incidence X-Ray diffraction (GI-XRD) showed that Oxygen atoms (O) replace Nitrogen atoms (N) in the cubic-Titanium Aluminum Nitride (c-TiAlN) lattice. The coating had ∼5.9 µm thickness, ∼6.3 at% O content and average roughness of Ra= 73.9 nm. High-temperature GI-XRD showed improved oxidation resistance up to 850 °C, at 900 °C the constituent oxides appeared. A columnar microstructure resulted in 21.72 GPa hardness and 418.31 GPa elastic-moduli. Adhesion tests showed critical loads > 19 N, with chipping and conformal-cracking. The pin-on-disk tests at room temperature (RT) showed coefficients of friction (COF) of 0.65 and 0.83 for the steel and the oxynitride, respectively. At 900 °C the COF decreased due to a tribolayer formation. Cyclic tribo-oxidation cause this tribolayer to wear and partially expose the substrate, showing wear mechanisms due to combined processes of the coating and the steel.