Oxidation Resistance Research Articles

Atom probe tomography investigation of sintered transition metal carbonitride - A Zr(C,N) study

Zirconium based nitrides, carbides and carbonitrides are highly technological compounds which received during the 50s and 60s huge interest due to their combination of metal and refractory properties. The interest reiterated recently due to the need of compounds with high electrical conductivity, corrosion and oxidation resistance, and neutron transparency with the rise of mobility electrification and nuclear power. Sintered Zr(C,N) is investigated with CHN elemental analysis combined to atom probe tomography (APT) to evaluate the composition and homogeneity of carbon and nitrogen from the bulk down to the nanometer scale. Results have shown a strong nitrogen loss and an enrichment in carbon which diffused from the graphite die and punch. Nevertheless, the composition is homogenous in the sample. Atom probe tomography suggests that the sintered alloy is sub-stoichiometric with carbon and nitrogen homogeneously distributed within the grain. The stoichiometry calculated corresponds to the estimation by Vegard’s law.

Predictive design of novel nickel-based superalloys beyond Haynes 282

Nickel-based superalloys are in great demand for harsh-service conditions involving high temperatures and oxidative environments. Haynes 282 stands out due to its excellent high-temperature properties and easy fabricability. However, the upper operation temperature of Haynes 282 is limited due to its relatively low liquidus temperature. Equipped with high-fidelity density-functional theory calculations and high-throughput experimentation methodology, we explored new compositional spaces that exhibit higher liquidus temperature and higher strength. While maintaining the manufacturability, the newly designed alloy shows improved strength and ductility at room temperature and better oxidation resistance up to 800°C. The new compositions showcase a minor change in the refractory and metalloid content can significantly impact the mechanical and oxidation performance of superalloys.

Nanocrystalline Y2O3-modified metal matrix composite coatings with improved resistance to thermocyclic oxidation and V2O5-induced type II hot corrosion

Incorporating reactive elements (RE) into turbine coatings is a well-established surface treatment. However, suboptimal RE concentrations can lead to compromised strength, heightened brittleness, and reduced adhesion. In contrast, RE oxides offer advantages of avoiding these detrimental effects, counteracting corrosion phenomena induced by V2O5 compounds and enhancing oxidation resistance. A notable challenge lies in optimizing RE oxide particle incorporation and understanding the influence of particles in coating microstructures. This study focuses on developing NiAl and Ni-Cr-Al type metal matrix composite (MMC) coatings on Inconel 617 (IN617), containing up to 11 vol% of Yttria (Y2O3) nanoparticles. Y2O3 nanoparticles and Ni were co-electrodeposited on IN617 followed by either pack aluminizing or a two-step chromizing and aluminizing process. An even distribution of Y2O3 nanoparticles was observed throughout the entire 100 μm coating thickness, leading to significant grain refinement in the sub-micron to nano range in both coating types. Y2O3-strengthened coatings were subjected to oxidation at 1100 °C and hot corrosion at 700 °C and were compared to their Y2O3-free counterparts. Present at grain boundaries, Y2O3 markedly enhanced the oxidation and corrosion resistance by reducing interdiffusion, improving the oxide scale adherence and binding V2O5, highlighting the potential of this method for advanced turbine blade coatings.

Effect of Al content on steam oxidation behavior for ferritic Fe-21Cr-xAl alloys

Given the focus on developing novel accident-tolerant materials for nuclear fuel cladding applications, FeCrAl alloys have been considered as one of the promising candidates. To optimize the composition of FeCrAl alloys, systematic studies are necessary to understand the elemental effect on oxidation behavior at normal and accident conditions. This work focuses on understanding how the presence of 3 wt.% and 8 wt.% Al in a Fe-21Cr alloy affects their steam oxidation mechanisms and oxide architecture in the steam environment at 400°C and 1200°C. Results show that increasing Al content has a beneficial effect on the oxidation resistance at both temperatures. At lower temperatures, the presence of Al promotes the formation of Cr2O3 and limits Fe oxidation resulting in the formation of thinner oxides with dual uniform layers rich in Cr2O3 on the outside and rich in Al2O3 on the inside. At 1200°C, increasing Al content from 3 to 8% reduces transient Fe and Cr oxidation and promotes a thinner protective α-Al2O3 oxide.

Unveiling the initial oxidation mechanism of a single crystal Ni-based superalloy with pre-deformation

The role of pre-deformation on the initial oxidation mechanism of a single crystal Ni- was revealed. With pre-deformation, the recrystallized grain boundaries and dislocations provided sites for the nucleation of Al2O3 and enhanced the diffusion flux of Al irrespective of γ/γ′ interface, γ′, and γ phase. Ultimately, a thin compact α-Al2O3 layer formed, improving the oxidation resistance. Without pre-deformation, Ni and Al atoms diffused along the γ'/γ interface, however, the Al-flux is insufficient to maintain the growth of Al2O3. As a result, a loose multilayer film formed on the surface, which decreased the oxidation resistance.

Critical processing parameters optimization and characterization of CrAlSiWN coating by industrial arc ion plating

CrAlSiWN coating has been deposited on SKH-51 steel by multi-arc ion plating technique. An orthogonal experimental approach is employed to optimize the processing parameters, including current, bias voltage, rotating stand speed, and duty cycle. The coating exhibits superior comprehensive properties under the following conditions: 150 A of current, -50 V to -200 V of bias voltage, 2 r/min of speed, and 80% duty cycle. The microstructure, mechanical and tribological properties, thermal stability, and oxidation resistance have been investigated. The results indicate that the CrAlSiWN coating consists of an fcc-(Cr, Al) N solid solution. The hardness is approximately four times that of the substrate (3827 HV) and the adhesion strength between the coating and substrate reaches 89.20 N. Wear mechanisms primarily involve abrasive and oxidation wear with a friction coefficient of 0.478. Additionally, CrAlSiWN coating exhibits excellent thermodynamic stability until 1100 °C when annealed under vacuum conditions and a remarkable oxidation resistance with a low oxidation weight growth rate of 0.08 mg/mm2 at temperatures up to 1100 °C.

Hot deformation behaviour of Swaged Zircaloy-4 at varying strain rate and its microstructural evolution

Zirconium alloy demonstrates a favourable combination of strength, ductility, low neutron absorption cross-section, as well as excellent corrosion and oxidation resistance. In the context of its application as a reactor component, the critical hot deformation behaviour of isothermally swaged Zr-4 alloy has been extensively studied. Different combinations of elevated temperatures (873 K to 1023 K) and strain rates (0.01 s−1 to 10/s) have shown enhancement in flow stress. Analysis of stress flow, microstructural changes, and activation energy behaviour was performed using a state-of-the-art thermomechanical simulator with 50% reduction in sample thickness. The modified Arrhenius equation was employed to correlate theoretical and experimental flow stress behaviour. EBSD was utilized to understand texture evolution in hot deformed samples, revealing a transformation from pure basal to basal plus pyramidal poles concerning the compression direction. Texture evolution played a significant role in microstructural development, further characterized through TEM, which showed influential characteristics like subgrain boundaries, dislocations, and precipitate behaviour. Dynamic recrystallization mechanisms in swaged Zr-4 hot deformed samples were analysed using bright and dark field TEM modes, which were subsequently correlated with other microstructural characteristics such as grain morphology and structural defects.

Effect of β phase size on the microstructure of thermally grown oxide in water vapor atmosphere at 1100 °C

The arc-melted and vacuum-casted CoNiCrAlHf alloys with a 7YSZ top coat were designed to develop a protective alumina scale at 1100 °C in water vapor content. Arc-melted CoNiCrAlHf alloys provided substantial improvements in oxidation resistance. In this work, the oxidation behavior and void distribution of thermally grown oxide (TGO) formed on CoNiCrAlHf alloys were analyzed. The Al2O3 crystal structure and void distribution were studied as a function of the grain size of the CoNiCrAlHf substrate. Numerous voids developed in the oxide scale, and coarse HfO2 particles segregated at the Al2O3 grain boundaries of vacuum-cast CoNiCrAlHf alloys. The uniformly distributed HfO2 particles prevented void formation in the oxide scale. As a result, the phase transformation of Al2O3 was effectively impeded in water vapor.

Enhanced service performances of in-situ Mg-Sialon/MgAl2O4 folding structure in low carbon Al2O3–C refractories: Phase reconfiguration of nano-MgSiN2

The utilization of in-situ ceramic combination effectively addressed the issue of weak bonding at the interface in low carbon Al2O3–C refractories, enhancing the material service performances. In this study, nano-MgSiN2 synthesized from molten salt was utilized for incorporation of Al2O3–C refractories, as well as in assessment of mechanical properties, thermal shock stability, oxidation resistance and corrosion resistance. The findings demonstrate that the molten salt medium can lower synthesis temperature and decrease particle size of nano-MgSiN2. In addition, nano-MgSiN2 undergone phase reconfiguration at 1500 °C to form Mg(g) and Si3N4(s). The folding structure Mg-Sialon/MgAl2O4 were formed through phase reconfiguration of Mg(g) and Si3N4(s). This change enhanced interfacial bonding strength of Mg-Sialon/Al2O3 and MgAl2O4/Al2O3. The mechanical properties and thermal shock stability of refractories were enhanced by novel reconfiguration technology, resulting in CCS value of 176.9MPa. Simultaneously, Mg-Sialon transformation facilitated the interconnection of the oxide layer, enhancing oxidation resistance and corrosion resistance.

Insulating refractories based on rice husk ashes functionalized by flame-sprayed alumina coatings for steel ingot casting

This study investigates a new insulating refractory material based on rice husk ashes (RHA) for its application in the steel ingot casting process. The excellent insulating properties of this material may improve heat- and energy balance during ingot casting. A flame-sprayed alumina coating is applied to provide chemical inertness of the substrate material against the steel melt. The refractoriness, oxidation resistance, phase evolution and thermal expansion of four different grades of RHA materials and phase evolution and thermal expansion of flame-sprayed alumina coatings are studied. The refractoriness of the RHA materials increased with increasing silica content, showing sufficient refractoriness up to 1600°C for SiO2>94wt%. Immersion tests with composite materials made from RHA substrate and a flame-sprayed alumina coating were successfully performed in a steel casting simulator. No deformation of the substrate material nor spalling of the flame-sprayed alumina coating was observed despite an immersion without preheating.

Preparation of BN@SiO2 nanofiber ceramic aerogel with ultralight, wave-transparent and heat-insulating for microwave sintering furnace

Thermal insulation devices play an extremely important role in enhancing microwave heating efficiency. However, existing wave-transparent insulation materials often exhibit high heat storage, low microwave transmittance at high temperatures, and poor oxidation and thermal shock resistance, hindering high-temperature applications for microwave sintering. To address this issue, we developed an ultralight and wave-transparent BN@SiO2 aerogel, which was fabricated through the in situ growth of SiO2 on the surfaces of BN fibers. The resulting composite aerogel demonstrated excellent high-temperature oxidation resistance and an impressively low density of 0.07g/cm3. Furthermore, the dielectric constant of the BN@SiO2 aerogel ranged from 2.58 to 2.80, and its dielectric loss tangent was as low as 5.13×10−3–7.98×10−3 within the 2–10 GHz frequency range. The successful synthesis of BN@SiO2 aerogel provides new progress and research ideas for the development of wave transparent and thermal insulation materials

Effect of MXene Ti3C2Tx in situ formed TiCx on oxidation behavior of high chromium white iron

In order to improve the oxidation resistance of high chromium white iron (HCWI), effect of 0.5–1 μm spherical and 5–10 μm lamellar TiCx sourced from Ti3C2Tx on oxidation behavior of high chromium white iron (Ti3C2Tx/HCWI) in air at 600 °C for 96 h was investigated. Oxidized surface displayed that the holes and peeling off caused by oxidation were found at different regions as a result of oxidative difference of double-dimensional-shaped TiCx in Ti3C2Tx/HCWI. Ti3C2Tx/HCWI exhibited improved oxidation resistance, thermodynamics and kinetics of oxidation were discussed.

Oxidative corrosion resistance of a CrxFeyNi1-x-y composition spread alloy film (CSAF) in dry air

Composition Spread Alloy Films (CSAFs) were used to study the resistance to oxidative corrosion of CrxFeyNi1-x-y alloys in dry air and determine the critical Cr composition, xCr∗, necessary to prevent bulk oxidation. CrxFeyNi1-x-y CSAFs were made using physical vapor deposition (PVD) and then oxidized in dry air between 100 – 500 °C for periods of 1 h. A sharp passivation boundary was observed at 300 °C separating alloys showing evidence of heavy oxidation from Cr-rich alloys that were passivated. X-ray photoelectron spectroscopy (XPS) depth profiling was used to measure the extent of oxidation and penetration depth of the oxide layer on either side of the passivation boundary. XPS measurements confirmed the presence of a critical Cr composition, xCr∗, ranging from 18 to 26 at.%. For alloys with xCr≥xCr∗, a sufficiently thick passivating layer of oxidized Cr, Cr(ox), had formed on the top surface preventing the oxidative corrosion of either Fe or Ni. On the other hand, when xCr<xCr∗, bulk oxidation was observed, with appreciable Fe(ox) and/or Ni(ox) measured on the surface and often penetrating through the entire alloy film thickness. The trajectory of xCr∗ plotted within CrxFeyNi1-x-y composition space supports the trend towards using higher Cr-content stainless steel grades in harsh oxidative environments.

Five new flavonoids and their pharmacological activities from Iris tenuifolia Pall.

Five new components including two new isoflavones, 5, 7, 2′, 3′-tetrahydroxy-6-methoxyisoflavone (1), 5, 7, 2′, 3′-tetrahydroxy-8-methoxyisoflavone (2), one flavonol 5, 3′, 4′-tetrahydroxy-7, 2′-dimethoxyflavonol (3), one flavanone (2S)-5, 7, 3′-trihydroxy-2′-methoxyflavanone (4), and one flavanonol (2R, 3R)-3, 5, 3′, 4′-tetrahydroxy-7, 2′-dimethoxyflavanonol (5), along with nine known flavonoids (6–14) were isolated from under ground parts of Iris tenuifolia Pall.. Their structures were elucidated by NMR and HRESIMS data and by comparison of CD spectra with compounds having similar structure. The separated compounds were evaluated for in vitro antioxidant activities by DPPH and ABTS. The α-glucosidase inhibitory activity of the compounds were evaluated with the pNPG method, the results indicated flavonoids were potential inhibitors of α-glucosidase. Moreover, in vitro anti-oxidative assay using flow cytometry indicated that compounds 1–5 showed strong oxidation resistance ability on C8D1A cells without affecting the cell viability.

Realizing the excellent oxidation resistance of an environmental barrier coating through aluminum surface modification

Realizing the excellent oxidation resistance of an environmental barrier coating through aluminum surface modification

Solvent-free one-step green synthesis of MXenes by “gas-phase selective etching”

Two-dimensional transition metal carbides and nitrides (MXenes) have attracted extensive attention due to their unique electronic properties and various applications for energy harvesting. However, the current synthesis procedures involve using fluoride-based aqueous solutions via reacting with Al-containing MAX phases. Besides, fluorine-free, cost-effective, and straightforward synthetic methods are rarely reported and need to be explored. Here, a solvent-free one-step gas-phase dry etching method, named “Gas-Phase Selective Etching”, was first proposed and used to etch different elements A (Al, Si, Sn, etc.) of MAX phases using the strong oxidation ability of halogens and hydrogen halides gases (Cl2, Br2, I2, HCl, HBr, and HI). The gas-phase etching can achieve a pure product of MXenes coupled with specific gas-induced functional groups. Meanwhile, MXenes powder can be directly obtained without the removal processes of etchants and by-products. Furthermore, the multilayer-MXene with -Cl functional groups (Ti3C2Cl2) has strong oxidation resistance and superior rate performance of capacitance. It provides us with an intelligent, cost-effective synthesis strategy that has a high yield and is safe, allowing for the promising mass production of MXenes.

Tailored high-temperature corrosion behavior of Cr coatings using high power impulse magnetron sputtering on ZIRLO alloys for accident-tolerant fuel application

To further enhance the oxidation resistance of Zirconium alloys during Loss of Coolant Accident (LOCA), protective Cr coatings were deposited in synchronized pulse bias mode through high power impulse magnetron sputtering (HiPIMS). The results showed the weight gain of the Cr coatings with synchronized pulse bias was reduced by approximately 61.7 % compared to that of the Cr coatings without synchronized pulse bias after 90 min of steam oxidation at 1200 °C. This was mainly attributed to the formed intense (200) preferred orientation of the Cr coatings with synchronized pulse bias during deposition, accelerating the recrystallization growth of the residual Cr layer in a high-temperature steam environment, thereby reducing the rapid diffusion pathways for oxygen. Moreover, the synchronized pulse bias induced Cr grains refinement, favoring the formation of a more compact Cr2O3 scale, and therefore efficiently inhibiting the diffusion of external oxygen to the underlying alloy.

Hollow carbon microsphere embedded with Fe nanoparticles for broadband microwave absorption

Nowadays, Fe-based microwave absorption materials still face crucial problems of poor oxidation resistance, lack of dielectric loss and narrow effective absorption bandwidth. In this work, we developed a feasible way of calcining and etching SiO2 microspheres coated Fe3+ and polydopamine (SiO2@Fe3+-PDA) to confine Fe nanoparticles (12 nm) in the hollow carbon microspheres with a thickness of 17 nm, which provides more interfaces and polarization sites to enhance microwave attenuation. With the increase of Fe content, the microwave absorption performance of the sample is gradually improved. When Fe content is 19.7 wt%, the sample has a minimum reflection loss (RL) of −30.9 dB and a broadband absorption bandwidth (RL ≤ −10 dB) of 11.9 GHz (6.1–18 GHz) at the thickness of 4.0 mm. The ultra-wide effective absorption bandwidth is ascribed to synergetic effect of Fe nanoparticles and carbon layer, which provide magnetic loss and dielectric loss, respectively. Moreover, the hollow structure extends the transmission path and induces the multiple scattering of the incident electromagnetic waves. The novel hollow Fe/C microspheres are promising as high-efficiency microwave absorbers with strong microwave absorption and broad absorption bandwidth.

Quantification and kinetics of nitrogen mass gain during high temperature oxidation of titanium in air

Improving the high-temperature oxidation resistance of titanium alloys in air is a prerequisite for extending their use in turbojet engines. A better understanding of the role of atmospheric nitrogen is required for this purpose. Here, we studied the insertion kinetics of nitrogen in titanium at 650 °C in air up to 100h. Moreover, the nitrogen mass gain, and its ratio over the total mass gain, were quantified as a function of the oxidation duration by using Nuclear Reaction Analysis. It was found that nitrogen inserts into titanium with a parabolic kinetics and a rate constant about 1500 times smaller than oxygen.

Effect of sputtering time on the microstructure and properties of MAO/CoCrFeNi composite coatings on TC11 alloy

In order to further improve the wear resistance and high-temperature oxidation resistance of titanium alloys, MAO/CoCrFeNi composite coatings with different sputtering times were prepared on TC11 alloy by micro-arc oxidation combined with radio frequency magnetron sputtering. The microstructure and phase composition of the composite coatings were investigated by scanning electron microscope and X-ray diffractometer. The wear performance at different temperature and high-temperature oxidation resistance of the composite coatings were studied. The results showed that as the sputtering time increases, the phase structure of composite coatings were all FCC phase, and the number of micropore on the composite coatings decreased; At room temperature, since the film thickness is proportional to the hardness, and higher hardness is conducive to the reduction of actual contact area between coating and grinding ball, so the composite coatings sputtered for 6 h had the narrowest wear scar width and the smallest wear weight loss, and its wear mechanisms were oxidative wear and adhesive wear; At 673 K, since the softening of the abrasive chips played a lubricating role, the composite coatings sputtered for 4 h produced the most abrasive chips, so it had the narrowest wear scar width and the smallest wear weight loss, and the wear mechanisms were mainly oxidative wear and adhesive wear, with slight abrasive wear; The composite coatings sputtered for 6 h was still tightly bonded to the substrate after oxidation at 1000K, and its weight gain is smaller than TC11, which indicated that it has the best high-temperature oxidation resistance.