Oxidation Resistance Research Articles

Enhancing Performance and Stability of High-Temperature Proton Exchange Membranes through Multiwalled Carbon Nanotube Incorporation into Self-Cross-Linked Fluorenone-Containing Polybenzimidazole.

Addressing critical challenges in enhancing the oxidative stability and proton conductivity of high-temperature proton exchange membranes (HT-PEMs) is pivotal for their commercial viability. This study uncovers the significant capacity of multiwalled carbon nanotubes (MWNTs) to absorb a substantial amount of phosphoric acid (PA). The investigation focuses on incorporating long-range ordered hollow MWNTs into self-cross-linked fluorenone-containing polybenzimidazole (FPBI) membranes. The absorbed PA within MWNTs and FPBI forms dense PA networks within the membrane, effectively enhancing the proton conductivity. Moreover, the exceptional inertness of MWNTs plays a vital role in reinforcing the oxidation resistance of the composite membranes. The proton conductivity of the 1.5% CNT-FPBI membrane is measured at 0.0817 S cm-1 at 160 °C. Under anhydrous conditions at the same temperature, the power density of the 1.5% CNT-FPBI membrane reaches 831.3 mW cm-2. Notably, the power density remains stable even after 200 h of oxidation testing and 250 h of operational stability in a single cell. The achieved power density and long-term stability of the 1.5% CNT-FPBI membrane surpass the recently reported results. This study introduces a straightforward approach for the systematic design of high-performance and robust composite HT-PEMs for fuel cells.

On the Possibility of Improving the Oxidation Resistance of High-Chromium Ferritic Stainless Steel Using Reactive Element Oxide Nanoparticles

AbstractHigh-chromium ferritic steels are current the only viable candidates for cheap interconnect materials for application in high-temperature solid oxide fuel and electrolyzer cells (HT-SOFCs/SOECs). The durability and operating characteristics of interconnects manufactured using these materials may be improved significantly by applying a protective-conducting MoCo2O4 coating and depositing an intermediate layer consisting of nanoparticles of Gd2O3—a reactive element oxide—on the surface of the steel substrate. The study demonstrated that the conditions of the thermal treatment of this layered system determine the efficacy of the applied modification with the reactive element. The persistence of this effect was tested over 7000 hours of quasi-isothermal oxidation in air at 800 °C.

High-Temperature Cyclic Oxidation Behavior and Microstructure Evolution of W- and Ce-Containing 18Cr-Mo Type Ferritic Stainless Steel.

Due to the recurrent starting and stopping operations of automobiles during service, their engines' hot ends are continually subjected to high-temperature cyclic oxidation. Therefore, it is crucial to develop ferritic stainless steels with better high-temperature oxidation resistance. This study focuses on improving the high-temperature cyclic oxidation performance of 18Cr-Mo (444-type) ferritic stainless steel by alloying with high-melting-point metal W and the rare earth element Ce. For this purpose, a high-temperature cyclic oxidation experiment was designed to simulate the actual service environment and investigate the high-temperature cyclic oxidation behavior and microstructure evolution of 444-type ferritic stainless steel alloyed with W and Ce. The oxide structure and composition formed during this process were analyzed and characterized using scanning electron microscopy/energy dispersive spectroscopy (SEM-EDS) and electron probe X-ray micro-analyzer (EPMA), in order to reveal the mechanism of action of W and Ce in the cyclic oxidation process. The results show that 18Cr-Mo ferritic stainless steel alloyed with W and Ce exhibits an excellent resistance to high-temperature cyclic oxidation. The element W can promote the precipitation of the Laves phase between the matrix and the oxide film, and the small-sized Laves phase can inhibit the interfacial diffusion of oxidation reaction elements and prevent the inward growth of the oxide film. The element Ce can refine oxide particles and reduce the thickness of the oxide film. CeO2 particles within the oxide film can serve as nucleation sites for the formation of oxide particles from reactive elements, and they also contribute to pinning the oxide film, thereby enhancing its adhesion.

Application of MgO/ZrO2 coating on 309 stainless steel to increase resistance to corrosion at high temperatures and oxidation by an electrochemical method

Abstract 309 stainless steel is one of the steels that have the highest resistance to corrosion and thermal oxidation compared to other steel grades, but it should not be used at temperatures higher than 980°C if there are temperature fluctuations. Additionally, 309 stainless steel is not designed for use in wet environments and has the least corrosion resistance. This study aims to cover 309 stainless steel with MgO/ZrO2 particles using a two-step electroplating deposition method and then sintering to increase its resistance to wet corrosion and oxidation in temperature fluctuations. The intermediate ZrO2 coating makes the outer MgO layer about two times thicker and reduces the corrosion current density. The morphology of the coatings was determined using scanning electron microscopy and X-ray diffraction, and oxidation resistance was determined using cyclic oxidation tests and the wet corrosion test of the corrosion solution. 3.5% NaCl was used. The results showed that the coated samples, due to the use of TiO2 middle layer and MgO protective layer in the electrochemical method, have a 2-fold increase in wet corrosion and an increase in hardness of about 77%, as well as an increase in oxidation resistance of 1.8% compared to the sample without coating. Also, the reason for using the electrochemical deposition method is for better surface smoothness and less porosity of the coating as well as its use on all metals compared to thermal spray methods.

Long-term oxidation of Ti3Al0.8Sn0.2C2 in air at 1200 °C

The addition of Sn into the raw materials is currently one of the most widely used methods to improve the purity and mechanical properties of Ti3AlC2. It follows in this work to investigate the oxidation behavior of the resulting Ti3Al0.8Sn0.2C2 at 1200 °C with the oxidation time up to 500 h. The oxidation kinetics shows that its oxidation resistance is much worse than that of common MAX phases including Ti3AlC2, Ti2AlC, and Cr2AlC. The oxide layer mainly consists of TiO2 and Al2O3, with only a small amount of SnO2 at the beginning of the oxidation stage. Cracks induced by the internal thermal stress penetrate through the entire oxide layer after only 1 h, which is an important reason for the rapid oxidation of the internal substrate layer. This work is expected to provide some inspiration and reference for Ti3Al0.8Sn0.2C2 used as the potential high-temperature structural material.

Depletion of squalene epoxidase in synergy with glutathione peroxidase 4 inhibitor RSL3 overcomes oxidative stress resistance in lung squamous cell carcinoma.

Lung squamous cell carcinoma (LUSC) lacks effective targeted therapies and has a poor prognosis. Disruption of squalene epoxidase (SQLE) has been implicated in metabolic disorders and cancer. However, the role of SQLE as a monooxygenase involved in oxidative stress remains unclear. We analyzed the expression and prognosis of lung adenocarcinoma (LUAD) and LUSC samples from GEO and TCGA databases. The proliferative activity of the tumors after intervention of SQLE was verified by cell and animal experiments. JC-1 assay, flow cytometry, and Western blot were used to show changes in apoptosis after intervention of SQLE. Flow cytometry and fluorescence assay of ROS levels were used to indicate oxidative stress status. We investigated the unique role of SQLE expression in the diagnosis and prognosis prediction of LUSC. Knockdown of SQLE or treatment with the SQLE inhibitor terbinafine can suppress the proliferation of LUSC cells by inducing apoptosis and reactive oxygen species accumulation. However, depletion of SQLE also results in the impairment of lipid peroxidation and ferroptosis resistance such as upregulation of glutathione peroxidase 4. Therefore, prevention of SQLE in synergy with glutathione peroxidase 4 inhibitor RSL3 effectively mitigates the proliferation and growth of LUSC. Our study indicates that the low expression of SQLE employs adaptive survival through regulating the balance of apoptosis and ferroptosis resistance. In future, the combinational therapy of targeting SQLE and ferroptosis could be a promising approach in treating LUSC.

Solvation structure design for stabilizing MXene in transition metal ion solutions

AbstractAlthough MXene has attracted great interest in diverse fields, it is susceptible to oxidation in water (H2O) with transition metal ions such as Co2+, Fe2+, and Cu2+, which is pronounced at high temperatures. This impedes the preparation of MXene‐based composites and their functional applications. Here, this study revealed that Co2+ increases the maximum and average atomic charge of H in H2O to improve the reactivity of H2O, which leads to the fact that Co2+ catalyzes the oxidation of Ti3C2Tx MXene. Furthermore, the addition of N,N‐dimethyl formamide (DMF) reduces the H2O activity and improves the oxidation stability of Ti3C2Tx in the presence of Co2+ via preferentially forming coordination bonds with Co2+. This strategy is also effective in enhancing the oxidation tolerance of Ti3C2Tx to Fe2+ in H2O. Moreover, it is feasible to enhance the oxidation stability of Ti2CTx MXene in H2O with the existence of Co2+. By virtue of these, the CoO/Ti3C2Tx composite was successfully prepared without obvious Ti3C2Tx oxidation, which is desirable to harness the advantages of Ti3C2Tx as the complementary component for lithium‐ion batteries. This work provides a straightforward paradigm to enhance the oxidation resistance of MXene in H2O in the presence of transition metal ions and at high temperatures, which opens a new vista to use MXene for target applications.

Advancements in bifunctional catalysts for unitized regenerative fuel cells: exploring polaronic conduction and heterostructure designs

This study investigates the development and performance evaluation of a bifunctional catalyst tailored for unitized regenerative fuel cells (URFCs), capable of facilitating both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in fuel cell and electrolyzer modes. The primary challenge addressed is the creation of electrocatalysts exhibiting high activity and corrosion resistance for oxygen reduction and water oxidation at the oxygen electrode. A novel catalyst structure based on La0.5Sr0.5Fe0.5Ti0.5O3(LSFT), i.e. LSFT/ZnO/LSFT with a thickness of ∼2 μ m, is explored within an environmentally friendly medium. This catalyst demonstrates superior performance characteristics, including reduced overpotential in HER and enhanced stability during oxygen/hydrogen evolution processes in neutral medium. This study identifies the formation of interfacial polarons and polaronic charge modulation resulting from the incorporation of ZnO in LSFT, leading to multifunctional OER/HER behavior. Notably, the proposed interfacial small polaron mechanism offers valuable insights into complex interfacial phenomena and holds promise for applications in diverse heterostructures involving layered 2D materials and transition metal oxides. Moreover, the robust LSFT/ZnO/LSFT catalyst exhibits exceptional stability, maintaining for 168 h of oxygen evolution at a constant potential of approximately 1.66 V for a current density of 1 A cm−2 in a neutral medium. These findings mark a significant advancement in URFC technology and present promising avenues for clean energy storage solutions.

Enhancing sulfur resistance of oxides in carbon monoxide oxidation by a high‐entropy‐stabilized strategy

AbstractIndustrial chemical processes require sulfur‐resistant catalysts, which reduce catalyst replacement costs and simplify process operations. Herein, a high‐entropy‐stabilized strategy was put forward for sulfur‐resistant catalysis. A spinel high entropy (Zn0.2Mg0.2Cu0.2Mn0.2Co0.2Al2O4) was introduced by ball milling process with aluminum isopropoxide as the main precursor. Zn0.2Mg0.2Cu0.2Mn0.2Co0.2Al2O4 possessed a high surface area of 171.2 m2 g−1, higher than typical high‐entropy oxides (HEOs). The high‐entropy spinel catalyst exhibited better SO2‐resistance performance in the oxidation of carbon monoxide, better than the simple oxides. The SO2‐resistance of Zn0.2Mg0.2Cu0.2Mn0.2Co0.2Al2O4 was primarily improved by reinforcing the stability of the oxide using a high‐entropy structure to decrease the absorption of SO2 on its surface. Any adsorbed SO2 on the surface of the HEO was then selectively trapped by sacrificial metal ions with stronger electron‐withdrawing ability, protecting the active center (Cu2+, Co2+) from poisoning. This work reveals the significance of high‐entropy structures in sulfur resistance.

Effects of Zr content on microstructure and properties of 9Cr ferritic/martensitic steel

The effect of the Zr content range in 0.03–0.63 wt% on the microstructure, mechanical properties and high-temperature oxidation behaviors of 9Cr ferritic/martensitic (FM) steels was investigated. The microstructural evolution of steels was studied using Thermo-Calc software, SEM, EBSD and TEM technologies. A full martensite structure was obtained in steels with various Zr contents. The small-sized M23C6 decrease and the larger-sized Zr(C, N) increase with the increasing Zr content, which leads to the increase of martensitic lath width and martensitic block size. The proper Zr content can enhance the oxidation resistance of steel, but Zr addition will reduce the mechanical properties. The decrease in strength and hardness can be ascribed to the reduction of precipitation strengthening and gain size strengthening. The increase in Zr content promotes the formation of Zr oxides, which reduces the formation of MnCr2O4 oxides and Cr2O3 oxides, and finally improves the oxidation resistance of steels.

Simultaneously enhanced antioxidation and wear resistance in UHMWPE molded plastic by adding natural polyphenol antioxidant

Ultrahigh-molecular-weight polyethylene (UHMWPE), with its excellent wear resistance and biocompatibility, has important application as artificial joints. The most commonly used method to improve its wear resistance is to introduce crosslinking through irradiation. However, free radicals are introduced after radiation, which are easy to cause inflammation in the human body. Some antioxidants, such as vitamin E (VE), need to be added. However, the addition of VE could reduce the crosslinking density of UHMWPE and worsen the wear resistance of the material. Therefore, obtaining new antioxidants that could eliminate free radicals without affecting or even improving the crosslinking density of materials during irradiation is an important subject worth exploring. In this paper, a kind of natural polyphenol substance, resveratrol (RSV), was introduced as a new antioxidant and crosslinking promoter during irradiation crosslinking of UHMWPE. RSV can better eliminate free radicals than VE and further improve the crosslinking density to obtain UHMWPE materials with excellent oxidation resistance and high wear resistance. The multi-active phenolic hydroxyl structure of RSV molecule provides its free-radical trapping ability, and the appropriate molecular size of RSV may promote the H-type crosslinking of UHMWPE, thereby increasing the crosslinking density. This work provides a new pathway for developing high-performance artificial joint prosthesis materials.

Mechanism of stable autotrophic nitrogen removal and NOB inhibition in low-sludge PN-Anammox system under non-temperature control and low ammonia environment

PN/Anammox, as an economical and effective nitrogen removal process, is of great significance for reducing carbon emission in municipal wastewater treatment. However, municipal wastewater has mainstream characterized of low temperature and low NH4+-N concentration, and NOB activity is difficult to inhibit, so achieving a stable PN process is the biggest challenge in the application of PN/Anammox to mainstream wastewater. This study developed a method for stable and efficient PN/Anammox based on very low sludge volume (MLVSS = 65 mg/L). Even when the temperature dropped to 15℃ or there was exogenous nitrite-oxidizing bacteria (NOB) interference, the system still had good inhibition of NOB activity. The total stable operation time was 386 days, and the NO2–-N accumulation efficiency could reach more than 90 %. Ellin6067, Nitrosomonas and Candidatus_Brocadia were the dominant functional microorganisms in the system. Nitrospira was the dominant genera of NOB with very low relative abundance (<0.04 %). The mechanism of the long-term stable mainstream PN/Anammox system showed that low sludge content was beneficial to light irradiation on microorganisms in the reactor, while nxrA, the functional gene of NOB, had weak light resistance and oxidation resistance, which makes the system had strong inhibition effect on NOB. The construction of this new system which does not depend on activated sludge volume and complex NOB activity inhibition strategy can better promote the practical application of PN/Anammox under mainstream conditions.

Ethyl fluoroacetate with weak Li+ interaction and high oxidation resistant induced low-temperature and high-voltage graphite//LiCoO2 batteries

Lithium-ion batteries (LIBs) operating at low temperature has always been a significant challenge. In this work, Ethyl fluoroacetate (EFA) was utilized as a single solvent to design a low-temperature electrolyte (LTE). The weak Li+-solvent interaction facilitates fast de-solvation process and improved low-temperature performance, while the high oxidation resistance and fluorine-rich electrolyte/electrolyte interface induced by the fluorinated groups enables wide operating voltage and stable cycling of the LIBs. The EFA-based electrolyte endows the high-voltage (4.45 V) Graphite//LiCoO2 pouch cell with prominent low-temperature adaptability (89.7 % capacity retention retains at −40 °C, and capable of charging at −20 °C) and outstanding cycling performance (87.7 % capacity retention after 400 cycles). This work sheds light on the design of high-voltage and low-temperature electrolytes for lithium-ion batteries.

Degradation behavior and osteogenic activity of octacalcium phosphate modified MgO coatings on magnesium

To further enhance the corrosion resistance and osteogenic activity of the porous micro-arc oxidation (MAO) derived MgO ceramic coating on biomedical magnesium (Mg), octacalcium phosphate (OCP) layers with different microstucture were prepared on MAO coating by chemical deposition (CD) method to fabricate MAO/CD composite coatings. The in vitro degradation behaviors of MAO/CD-coated samples were evaluated by immersion in simulated body fluid (SBF) and electrochemical impedance spectroscopy (EIS) measurement. Their effects on in vitro MC3T3-E1 cell differentiation were investigated by examining alkaline phosphatase (ALP) activity and expression of main osteogenic-related genes. The in vitro immersion tests show that MAO/CD coatings rarely experience destruction and only micro-cracks occur after 96 h. EIS tests indicate that MAO/CD coatings slow down the degradation rate of Mg observably. In addition, MAO/CD coatings improve osteogenic differentiation of MC3T3-E1 cells compared to MAO coating, which is ascribed the lightened alkalization of the surrounding medium as well as up-regulated intracellular Ca2+. MAO/CD coating deposited in 2 h endows Mg the slowest degradation rate and excellent osteogenic differentiation induction activity.

3D printed curcumin-based composite film for monitoring fish freshness

Curcumin/oregano oil Pickering emulsion (COPE) stabilized by pumpkin seed protein/pectin complex was prepared. COPE has excellent stability in 50 d storage period. Using COPE/ potato starch (PS)/polyvinyl alcohol (PVA) based gel as ink, pH-sensitive indicator film was developed by 3D printing technology. The morphology, mechanical strength, water resistance, oxidation resistance and bacteriostasis of different COPE/PS/PVA films were discussed. The nozzle size had a significant impact on the thickness of 3D printed PS/PVA membranes, with the average thickness of the membranes produced using 0.26 and 0.41 mm nozzles being about 0.12 and 0.18 mm, respectively. COPE can obviously improve the antioxidant and antibacterial performance of PS/PVA membranes. The membrane containing 5%, 7% and 10% COPE had a scavenging rate of ABTS free radicals of over 90% and an inhibitory rate of over 10% on S. aureus and E. coli. The prepared 3D printed two-color label realized the color change process of 4D printing under the stimulation of moisture and TVBN during storage of grass carp. In a word, 3D printing has great potential in online production of food indication labels with different shapes, sizes and functional characteristics, and is suitable for the manufacture of smart food packaging.

CALPHAD-Based Modeling and Experimental Validation of Silicon Effect on the Solidification Behavior of Novel SiNb Cast Irons

AbstractThe low oxidation resistance of SiMo ductile cast irons used as exhaust manifold material at high temperatures necessitates the development of new generation ductile cast iron compositions. New alloy designs can be made using CALPHAD methodology, and solidification sequence, segregation and critical phase transformation temperatures can be determined, especially for the solidified bulk materials. Thus, in commercial practicality, castable compositions with a raised A1 temperature can be obtained. In this study, novel SiNb cast irons with varying silicon contents were developed as candidate materials for exhaust manifolds. Solidification sequence, microsegregation, phase transformations, equilibrium phases of hypereutectic compositions containing 4 to 7 wt pct Si were calculated by CALPHAD-based modeling. The bulk materials of the studied compositions were cast as Y blocks and metallurgical analyzes were carried out. Studies revealed that; (i) in the ferritic matrix of the cast irons, graphite, Nb-rich carbides and some pearlite existed, (ii) pearlite formation was due to the negative segregation of silicon and positive segregation of manganese during solidification, (iii) as silicon content increased the amount of silicon dissolved in ferrite phase increased in the solidified structure and as a result pearlite formation decreased at the cell boundaries, and amount of vermicular graphite increased, (iv) depending on the silicon content the critical A1 temperature varied between 860 °C to 1013 °C and these values were higher than that of SiMo cast iron. All these findings revealed that SiNb cast irons had phase stability at higher temperatures compared to SiMo cast iron.

Astaxanthin attenuates UV-irradiation aging process via activating JNK-1/DAF-16 in Caenorhabditis elegans.

Astaxanthin (AST) is a xanthophyll carotenoid with strong oxidation resistance, which can effectively scavenge various free radicals and protect organisms from oxidative damage. AST is also known to have prominent anti-aging effects, but the underlying mechanism of AST in anti-radiation aging is largely unknown. In this work, we applied ultraviolet (UV) irradiation to accelerate the aging of Caenorhabditis elegans (C. elegans) and treated the nematodes with AST to explore whether and how AST could attenuate the radiation-induced aging effect. Our results showed that AST improved the survival rate of C. elegans, reduced the aging biomarkers, and alleviated the mitochondrial dysfunction caused by the irradiation. Based on the transcriptome sequencing analysis, we identified that the key genes regulated by AST were involved in JNK-MAPK and DAF-16 longevity signaling pathways. Furthermore, we employed jnk-1 and daf-16 mutants and verified the role of the JNK-1/DAF-16 signaling pathway in the anti-aging effect. As such, this study has not only demonstrated that AST can resist the aging process caused by UV-irradiation but also revealed the anti-aging mechanism of AST through JNK-1/DAF-16 activation in C. elegans.

Effect of oxygen substitution and oxycarbide formation on oxidation of Ti3AlC2 MAX phase

AbstractMAX phases, ternary transition metal carbides and nitrides, represent one of the largest families of layered materials. They also serve as precursors to MXenes, two‐dimensional (2D) carbides and nitrides. The possibility of oxygen substitution in the carbon sublattice, forming oxycarbide MAX phases and MXenes, was recently reported using secondary ion mass spectrometry. However, while the effect of oxygen substitution on the properties of MXenes was investigated, little is known about its effect on the properties of MAX phases. Here, we explore the influence of process parameters (e.g., particle size, synthesis temperature, annealing time, etc.) and oxygen presence in the lattice on the oxidation resistance of Ti3AlC2 MAX phase powders. We show that X‐ray diffraction measurements can identify oxygen substitution and assist in selecting MAX precursors to synthesize stable and highly conductive MXenes. Eliminating the substitutional oxygen from the MAX phase lattice increases the onset of oxidation by 400°C, from approximately 490 to 890°C. Finally, we discuss the impact of oxygen substitution in the MAX phases on the synthesis of MXenes and their resulting properties.

Effect of difference in microstructure of rare refractory metal silicate doping matrix on oxidation behavior and mechanism of C/SiC composites

Doping refractory metal silicates into the matrix of C/SiC composites is an effective means to improve their oxidation resistance. Previous studies have demonstrated that doping HfSiO4 matrix availably enhanced the oxidation resistance of C/SiC composites, but the high raw material cost of HfSiO4 limits its widespread application. This paper attempts to introduce ZrSiO4 matrix, which has lower raw material cost and similar properties to HfSiO4, into C/SiC matrix through the same process. To clarify whether the microstructure of the refractory metal silicate doped matrix significantly impacts the oxidation behavior of C/SiC composites, the preparation temperature of ZrSiO4 was increased to 1100 °C. The densification effect, oxidation behavior, and related mechanisms of C/SiC composites doped with ZrSiO4 matrix were investigated and compared in detail with the previously studied C/SiC composites doped with HfSiO4 matrix. Results show that the oxidation resistance behavior of C/SiC composites is relatively sensitive to the microstructure of the refractory metal silicate-doped matrix. At lower preparation temperatures of refractory metal silicates, the particle size of the composite matrix is significantly refined, which is conducive to improving the matrix densification degree of the composites and protecting more carbon fibers from erosion by the oxidizing environment, thus achieving a better oxidation resistance modification effect.

Nanoprecipitate strengthened, alumina forming austenitic stainless steels for elevated temperature applications

Low cost stainless steels (SS) with high performance, especially with good mechanical properties and oxidation resistance at high temperature, are continuous pursuit for manufacture industry. To achieve good combination of mechanical properties, oxidation resistance and cost, nanoprecipitate strengthened alumina forming austenitic (NSAFA) SS have been developed by removing expensive elements such as Nb and Ta, lowering Ni concentration in Fe–26Ni–15Cr-1.5Mo-(2.8–3.5)Al-(1–2.35)Ti (wt.%) alloys. Microstructure investigation demonstrates that NSAFA SS are strengthened by L12 structured (Ni, Fe)3(Al, Ti) γ′ nanoprecipitates with area fraction around 25%–40%. Oxidation experiments (750 °C/480 h) in air demonstrates that all the NSAFA steels have alumina forming ability. In addition, it is found that Al and Ti are all necessary for γ′ nanoprecipitates, but additional Al and Ti facilitate formation of the Ni2AlTi phase. To ensure high volume fraction of γ′ nanoprecipitates and reduce Ni2AlTi phase, 2.8–3.0 wt% Al and 1.8–2.35 wt% Ti are preferred. Benefit from the high volume fraction of γ′ nanoprecipitates, yield strength of NSAFA steels is much higher than that of Fe-base superalloy (e.g., A286) and can compare to some Ni-base superalloys (e.g., Hayners 282 & Inconel 740H).