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Purpose: To measure and compare the mean temperature values due to heat generated during the grinding of different prosthetic materials with diamond burs using a high-speed instrument with and without water cooling. Materials and Methods: In total, 120 disk-shaped specimens (10 × 2 mm), each with a smaller disk in the center (3 × 2 mm), were fabricated from yttrium-stabilized zirconia, monolithic zirconia, glass-ceramic, indirect composite, polyetheretherketone (PEEK), and cast metal (Ni-Cr alloy). The specimens were divided into six groups (n = 20) according to material type. The specimens in each group were ground continuously with a high-speed handpiece and diamond burs with (n = 10) and without (n = 10) water cooling until the smaller disks were removed. Two different methods (thermocouple and thermal camera) were used to measure the temperature during the grinding process. Results were analyzed using two-way ANOVA and paired-samples t test (P < .05). Results: PEEK had the lowest mean temperature and metal had the highest values, both with and without water cooling, according to data measured with a thermocouple. Zirconia and monolithic zirconia samples without water cooling had the highest mean temperature when measured with a thermal camera. Both with and without water cooling, composite samples had the lowest mean temperatures for thermal camera measurements. Conclusions: Water cooling is strongly recommended when grinding all prosthetic materials. The heat transferred to the supporting teeth may depend on the thermal conductivity of the material used. [ABSTRACT FROM AUTHOR]

Purpose: This article targeted to experimentally examine the impact of several considered process parameters namely, applied voltage (AV), tool feed rate, electrolyte concentration and pulse frequency (PF), on the material removal rate (MRR) and radial overcut (ROC) while performing shaped tube drilling of aviation grade Inconel 625 super alloy through electrochemical machining principle. Further, an attempt has also been made to develop mathematical models for the process responses along with advanced optimization with evolutionary methods. Design/methodology/approach: The central composite rotatable design matrix was used to scheme out the experiments in the present study. The consistency and accuracy of the developed mathematical models were confirmed through statistical results. Additionally, a field emission scanning electron microscope analysis was conducted to assess and analyze the microstructure of the machined work samples. The study also seeks to optimize the selected process inputs for MRR and ROC through the implementation of the desirability method, particle swarm optimization (PSO) and Teaching Learning-Based Optimization (TLBO). Findings: The ROC is significantly influenced by the input parameters, specifically the PF and AV. Less ROC values were observed when the high PF with moderate AV. The minimum and maximum values of ROC and MRR were obtained as; 135.128 µm and 380.720 µm; 1.37 mg/min and 2.3707 mg/min, correspondingly. The best optimized confirmatory results were obtained through the TLBO approach, with an MRR value of 3.1587 mg/min and a ROC of 71.9629 µm, in comparison to the PSO and desirability approaches. Originality/value: The various challenges associated with the productive machining of aviation grade Inconel 625 superalloy have been explored experimentally. The conducted experimentation has been performed on the in-house fabricated micro-electrochemical setup capable of performing a variety of advanced machining operations at the miniaturized level. Further, the application of shaped tube drilling while processing aviation grade Inconel 625 superalloy has been explored with the developed micro-ECM set-up. Moreover, the performed microstructure analysis of the machined work samples has elaborated and explored the various associated surface integrity aspects which are quite crucial when it comes to real-life aerospace-related applications. The utility of designed experiments has further made the attempted experimental analysis more fruitful and qualitative too. [ABSTRACT FROM AUTHOR]

In this work, we report a newly developed γ–γ′-strengthened Ni–Co–Cr–Al–Ti-based medium-entropy alloy (MEA) with a low density of 7.84 g cm−3, designed based on the CALPHAD approach for turbine disk applications. The alloy exhibits coarsened γ′ precipitates with an average diameter of 285 ± 70 nm and irregular eutectic (γ + γ′) phases in the interdendritic region in the as-cast condition. In contrast, fine γ′ precipitates with an average diameter of 154 ± 26 nm are uniformly distributed in the dendritic region. The alloy demonstrates outstanding tensile properties, including a yield strength of 833 ± 4 MPa, ultimate tensile strength of 1080 ± 14 MPa, and ductility of 22 ± 2 pct in the as-cast condition. Due to its low density and high specific yield strength (106 MPa g−1 cm−3), this alloy has the potential to be a viable alternative to Waspaloy and other nickel-based superalloys. [ABSTRACT FROM AUTHOR]

In this paper, we introduce an entirely new solar absorber design—a multi-layer periodic stacked structure. Through coupling effects, this design has perfect ultra-wideband absorption characteristics. The absorber structure is composed of four absorption units with varying cycle lengths, which are cyclically stacked on the surface of the refractory metal Cr. Each cycle encompasses three-layer nanosheets of Ti–SiO2–GaAs. We verify through finite difference time domain method (FDTD) simulations that the absorber achieves an absorption efficiency of 97.8% within the wavelength range of 280 nm to 3000 nm, with an average efficiency of 96.6% under the AM1.5 standard solar spectrum. The absorber can achieve such a remarkable absorption effect because of surface plasmon resonance (SPR) and Fabry–Pérot resonance effects. At 1500 K, this structure exhibits a thermal radiation efficiency of up to 97.83%. Furthermore, the design is not affected by polarization and it is less affected by the incident angle of the light source. These absorption spectra remain consistent regardless of whether it is in the TE or TM mode. Even when the angle of incidence is increased to 60 degrees, the absorption efficiency remains high. Its unique structure and excellent performance characteristics provide higher solar energy efficiency. These outstanding features enable solar absorbers to have broad application potential in improving solar energy efficiency. [ABSTRACT FROM AUTHOR]

In this study, the creep tests of three PM Ni-based superalloys with different Zr contents were carried out at 700 °C/780 MPa, 750 °C/550 MPa and 800 °C/400 MPa, respectively. The effect of Zr on creep deformation behaviors was studied by OM, SEM, EBSD and AC-STEM. The results show that the addition of appropriate Zr (0.1 wt.%) inhibits crack initiation and premature cracking, prolongates the creep rupture time, reduces the minimum creep rate, and increases the proportion of steady-state creep duration. However, excessive Zr content (0.5 wt.%) can promote the continuous precipitation of μ, σ, and Ni7Zr2 phases at the grain boundaries, which is easy to become a crack source and reduce the creep performance. In general, the alloy with 0.1Zr addition has high creep strength, low tendency of intergranular cracking at high temperature, and the best overall creep performance. This study provides a theoretical basis for the appropriate addition of Zr in PM Ni-based superalloys and provides some ideas for the optimization of alloy composition and design of novel PM Ni-based superalloys. [ABSTRACT FROM AUTHOR]

There is a growing focus on sustainability, characterized by making changes that anticipate future needs and adapting them to present requirements. Sustainability is reflected in various areas of materials science as well. Thus, more research is focused on the fabrication of advanced materials based on earth-abundant metals. The role of iron and its alloys is particularly significant as iron is the second most abundant metal on our planet. Additionally, the electrochemical method offers an environmentally friendly approach for synthesizing multifunctional alloys. Thus, iron can be successfully codeposited with a targeted metal from complexing electrolytes, opening a large horizon for a smart tuning of properties and enabling various applications. In this review, we discuss the practical aspects of the electrodeposition of iron-based alloys from complexing electrolytes, with a focus on refractory metals as multifunctional materials having magnetic, catalytic, mechanical, and antimicrobial/antibacterial properties with advanced thermal, wear, and corrosion resistance. Peculiarities of electrodeposition from complexing electrolytes are practically significant as they can greatly influence the final structure, composition, and designed properties by adjusting the electroactive complexes in the solution. Moreover, these alloys can be further upgraded into composites, multi-layered, hybrid/recovered materials, or high-entropy alloys. [ABSTRACT FROM AUTHOR]

Examination of microstructural evolution and mechanical properties of the laser powder bed fusion (LPBF)-processed Inconel 939 (IN939) after direct aging (DA) and solutionizing (S) followed by aging (SA) may enable the development of strategies for optimizing the microstructure with excellent mechanical properties. Herein, the samples that were solutionized followed by water quenching and two-step aging showed commendable room temperature mechanical properties with 0.2% yield strength of 930 MPa and 21% elongation to failure. DA at 800 °C retained a preferred {100} texture from the as-printed condition with 20–50 nm semi-coherent γ′ (Ni3Al(Ti)) precipitates, while upon DA at 1000 °C, the microstructure comprised coarsened γ′ along with plate-shaped eta phase (η-Ni3Ti). The {100} texture continued to be present after SA also. The creep behavior of the optimized LPBF IN939 was evaluated, and the activation energy, stress exponent and Larsen–Miller parameter were established. The critical role of primary γ′-precipitates and carbides in determining creep response has been elucidated. The relative merits of DA versus SA in terms of structure–property relationships are highlighted. This study, therefore, paves a path for the development of simple and relevant strategies for improving the overall mechanical behavior of additively manufactured Ni-based superalloys that cannot be processed through conventional thermo-mechanical routes. [ABSTRACT FROM AUTHOR]

The present paper reports the design of a new class of γ/γ′ containing high-strength CoNi-based superalloys in the Co–Ni–Al system by the addition of Ta and Ti. The designed alloys with compositions Co–30Ni–10Al–2Ta–xTi (where x = 0, 2, 4 at.%) exhibit a γ/γ′ microstructure suitable for moderate temperature applications (≤ 800 °C) requiring exceptional specific strength. The 3D APT compositional analysis of the γ and γ′ phases indicates a Co-rich matrix, while the ordered γ′ precipitates are Ni-rich with a stoichiometry of (Ni,Co)₃(Al,Ta). The subsequent addition of Ti up to 4 at.% increases the Ni partitioning to the γ′ precipitates, enhancing their stability. Furthermore, the addition of 4 at.% Ti increases the γ′ solvus temperature by 170 °C, from 950 to 1120 °C, and concurrently decreases the mass density from 8.50 to 8.34 g/cm3. A positive correlation between yield strength and temperature is observed in the Ti-containing alloys, with maximum yield strengths and specific yield strengths of 1025 ± 25 MPa and 122 MPa·g⁻1·cc, respectively, in the 2Ta2Ti composition, and 1030 ± 20 MPa and 123 MPa·g⁻1·cc, respectively, in the 2Ta4Ti composition. Long-term stability studies, including microhardness measurements and quantitative assessments of microstructural features, demonstrate excellent microstructural stability and resistance to coarsening in the 2Ta4Ti alloy at 900 °C. This work provides the opportunity to further design low-mass-density CoNi-based alloys with superior performance in the medium-temperature domain required for Advanced Ultra-Super-Critical (AUSC) power plants. This paper is part of a special volume in Journal of Materials Science in honor of Professor Kamanio Chattopadhyay, renowned for his research in our field and his significant contributions to the development of novel alloys for various engineering applications. In his early 60 s, Professor Chattopadhyay's group pioneered the discovery of low-density Co-based superalloys with a γ/γ' microstructure closely resembling that of Ni-based superalloys. This work involves some of the alloy compositions we conceived during our doctoral thesis work with him. [ABSTRACT FROM AUTHOR]

In this work, we designed a novel cross-process matching method and technology through sensing signals and dimensional fitting. Specifically, we mixed the electrochemical machining and sinking electrical discharge machining methods with intelligently designed special-shaped electrodes to effectively enable virtual measurement and dimension maintenance by developing intelligent electrode-processing technology for nickel-based superalloy special-shaped electrodes. The technique can help directly adjust the product accuracy of special-shaped holes on the basis of the relationship between the amount of material removed and the current by revealing errors across processing, obtaining feedback, and maintaining accuracy through matching methods without offline measurement. With a lot of time and design adjustment parameters, this method can provide more accurate and faster results than the traditional method. The electrode wear after 17 h of continuous processing is <10%. Processing accuracy control during discharge is <±0.5 pm. The processing time of the rough/medium machiningprocess is ≤24 h, which is an increase of ≥40%. Moreover, the electrical machining process optimization improved aerospace diffuser processing efficiency by 30%. [ABSTRACT FROM AUTHOR]

Surface science instruments require excellent vacuum to ensure surface cleanliness; they also require control of sample temperature, both to clean the surface of contaminants and to control reaction rates at the surface, for example, for molecular beam epitaxy and studies of heterogeneous catalysis. Standard approaches to sample heating within high vacuum chambers involve passing current through filaments of refractory metals, which then heat the sample by convective, radiative, or electron bombardment induced heat transfer. Such hot filament methods lead to outgassing of molecules from neighboring materials that are inadvertently heated; they also produce electrons and ions that may interfere with other aspects of the surface science experiment. Hot filaments may even disintegrate when used in the presence of gases introduced to induce surface reactions on the sample. Optical heating using lasers can deliver energy directly to the sample, ensuring that only the sample is heated and surroundings within the vacuum chamber are not, while simultaneously eliminating the need for hot filaments. Despite this advantage, optical heating is not commonly employed—such methods are considered complex, expensive, and unreliable. More fundamentally, surface scientists are often interested in metallic samples, whose reflectivity may limit the efficiency of laser heating. In this paper, we describe a simple and inexpensive sample heater based on a commercial diode laser, whose heating efficiency is enhanced by a concave aluminum mirror placed behind the sample. The geometry of the reflector and sample ensures that a stable optical cavity is produced. Using only 26 W of laser power directed to the sample with a fiber optic, a 1-cm diameter × 2-mm thick Pt sample could be heated to 1400 K within 1 min. Excellent programmable temperature control and long-term temperature stability are also demonstrated. Sample heating to 900 °C was performed with negligible increase in chamber pressure. The entire setup comprises components costing less than typical electron bombardment heaters. [ABSTRACT FROM AUTHOR]

To enhance the high-temperature oxidation resistance and mechanical properties of a secondgeneration nickel-based superalloy, various concentrations of lanthanum (La) ranging from 5.0×10-5wt.% to 3.4×10-4wt.% are added to the alloy. The microstructure of the nickel-based single crystal superalloy with trace of La was examined by means of SEM, EDS and TEM. Results show the addition of La decreases the segregation of elements and increases the amount of γ/γ' eutectics of the as-cast alloy, and in the interdendritic region, the growth of eutectics is accompanied by the growth of strip clusters composed of Ni5La and Ni3Ta. As the La content in the alloy increases, the proportion of Ni5La in the cluster increases. After heat treatment, incipient melting occurs in the cluster regions, leading to an increase in microporosity compared to the original as-cast samples. Furthermore, the heat treatment alters the shape of the clusters from a strip morphology to an elliptical one, and it changes their composition from Ni5La and Ni3Ta to a combination of Ni5La, Ni3Ta, and MC carbides. [ABSTRACT FROM AUTHOR]

Polyethylene (PE) is the most prevalent type of plastic waste and also the most challenging to depolymerize because of its inert carbon‐carbon (C−C) bonds.[1] High temperature and noble metals are usually required for depolymerization.[2] To avoid using noble metals, costly reagents and harsh reaction conditions, it is worthwhile but challenging to explore new reaction pathways.[3] We report an unprecedented mechanochemical reaction of PE and water to result in shorter‐chain alkanes, alkenes, alcohols, and ketones (Cn, where n≲50), with above 80 % of starting carbon converted into these products, which could be a valuable feedstock for re‐entering chemical value chains. This reaction is driven solely by ball milling, without heating and pressurizing. No costly catalysts are used. Instead, only earth‐abundant Al2O3 was milled with reactants. [ABSTRACT FROM AUTHOR]

Nickel-based superalloy GH4169 has gained significant prominence in aerospace and power-generation sectors due to its exceptional resistance to fatigue, creep and corrosion at high temperatures. However, wear on the contact surface remains a concern during its operational lifespan, as it can lead to crack initiation and reduce the service life of the alloy. Therefore, this study aims to comprehensively investigate the dry-sliding wear behaviors of the GH4169 superalloy under various conditions, including temperatures, applied loads and sliding speeds via a ball-on-disc tribometer. The results obtained from the study indicate that the wear rate of the GH4169 superalloy is initially high at room temperature. However, as the temperature increases to 525 °C, the wear rate significantly decreases. Subsequently, with further temperature increase to 650 °C, there is a slight rise in the wear rate. However, the findings regarding the friction coefficient present a conflicting trend compared to the wear rate. Under the same testing conditions, the wear rate of the GH4169 superalloy at 525 °C and 650 °C demonstrates a significant reduction of 21% (0.0774 × 10–4 mm3/N.m) and 19% (0.0785 × 10–4 mm3/N.m), respectively; when compared to room temperature (0.0935 × 10–4 mm3/N.m). Besides, at room temperature, the wear track depths measure approximately 34 ± 2 µm and 55 ± 3 µm for applied loads of 20 N and 60 N, respectively. These values indicate a significant wear depth under ambient temperature conditions. On the other hand, at 525 °C, the wear track depths are slightly lower compared to those at RT. The measured depths at 525 °C amount to approximately 25 ± 2 µm and 38 ± 2 µm for applied loads of 20 N and 60 N, respectively. At high temperatures and low applied loads, the wear mechanism of the GH4169 superalloy is mainly abrasion. However, at low temperatures and high applied loads, the wear mechanism becomes more complex, involving abrasion as well as oxidation, delamination, softening and melting. This study offers valuable insights into how different wear testing parameters impact the tribological characteristics of the GH4169 superalloy. [ABSTRACT FROM AUTHOR]

In recent years, there has been a notable initiation or acceleration in the production of new aeronautical engines. This surge is coupled with a global commitment to reducing emissions and mitigating noise generated by gas turbines used in aeronautical applications. A critical component in this context is the aeronautical casing. The manufacturing process is intricate and time-consuming, compounded by the complexity of the clamping system, which poses a significant challenge to productivity. This study undertakes a comprehensive analysis of the critical variables essential for the optimal manufacturing of a zero-defects large-scale casing. The examination encompasses design criteria, raw materials, constraints related to clamping systems and tooling, and process monitoring. Ultimately, the exploration extends to the examination of more sustainable manufacturing techniques. To facilitate this, a case study involving the fabrication of a life-size aeronautical casing is undertaken. [ABSTRACT FROM AUTHOR]

Nowadays, the combination of additive manufacturing technologies, together with the use of materials such as Inconel 718, opens new opportunities in the manufacture of aeronautical turbines. However, parts obtained directly through additive manufacturing are far from being considered suitable in their initial state, as they exhibit a poor surface finish that compromises their mechanical characteristics. Common among the defects found in such components are ridges stemming from thermal deformations during the powder fusion process. Therefore, abrasive brushing emerges as the prevalent method to rectify these surface imperfections. However, conventional roughness indicators prove insufficient in accurately characterizing such local defects during surface analysis. Consequently, this study investigates surface conditions of Inconel 718 parts produced through additive manufacturing, particularly focusing on defects caused by peak alignments along the powder fusion direction. Thus, a series of frontal brushing operations were conducted under varying conditions, with the aim of increasing the feed rate to address these defects. Subsequently, the effectiveness of the brushing process was assessed through the calculation of peak areas. The analysis of this indicator revealed that the maximum feed rate enabling complete removal of the peak marks was 500 mm/min. [ABSTRACT FROM AUTHOR]

In order to investigate the internal temperature characteristics during the operation of gap-type extra-high-strength steel core heat-resistant aluminum alloy conductors and carbon fiber composite core flexible aluminum conductors, a finite element simulation model based on the thermal balance equation of conductors is constructed, taking the electromagnetic-flow-solid-heat multiphysics field coupling into consideration. The simulation results are in good agreement with the theoretical calculation results of the thermal balance equation. The results indicate that, under identical conditions, the average temperature, radial temperature difference, and maximum temperature of the carbon fiber composite core flexible aluminum conductor with equivalent specifications are all lower than those of the gap-type extra-high-strength steel core heat-resistant aluminum alloy conductor. Furthermore, due to the significantly smaller radial temperature difference of the air gap-type extra-high-strength steel core heat-resistant aluminum alloy conductor and the carbon fiber composite core flexible aluminum conductor compared to conventional steel core aluminum stranded conductors under the same conditions, the maximum temperatures of the gap-type extra-high-strength steel core heat-resistant aluminum alloy conductor and the carbon fiber composite core conductor are approximately 4% and 8% lower, respectively, under natural convection, and approximately 8% and 14% lower, respectively, under forced convection, compared to conventional steel core aluminum stranded conductors. [ABSTRACT FROM AUTHOR]

The evaporation of chromium at elevated temperatures in vacuum, commonly employed in the processing and heat treatment of Ni–Cr–Fe heat-resistant alloys, has been investigated. Two variants of these alloys, each containing distinct alloying elements, were exposed at 1100 °C for durations of 3 to 500 hours. These exposures were conducted within a vacuum environment, both with and without applied stress. During the experiments, the samples displayed the development of a carbide-free layer (M23C6/M7C3) with thicknesses ranging from 10 to 100 μm. Employing Energy Dispersive Spectroscopy (EDS), the composition of the alloys was analyzed as a function of depth beneath the surface. Notably, the samples exhibited a pronounced gradient of chromium content. This gradient corresponded to the dimensions of the carbide-free layer, suggesting that the dissolution of carbides is due to the chromium evaporation process. A noticeable difference in the behavior of the two alloys was identified and deduced to be related the effect of aluminum on the development of concentration gradients and the associated surface evaporation of chromium. These observations were interpreted within the framework of a diffusion-based evaporation model which shed light on the intricate interplay between alloy composition, carbide dissolution, and chromium evaporation during high-temperature exposure. [ABSTRACT FROM AUTHOR]

The heat treatment process plays a significant role in enhancing the performance of turbine disks made from nickel-based superalloys. However, the residual stress that emerges during quenching can lead to distortion or even cracking in turbine disks made of nickel-based superalloys. The stress evolution in bulk nickel-based superalloy, together with the strengthening of precipitation, was investigated in the current research, aiming to reveal the evolution quantitatively and to support the process design. The residual stress was predicted using finite element (FE) simulation and the contour method was employed to validate the simulation. The simulated results agreed well with the experimental findings and the validity of the simulation was thus proved. The simulation demonstrates that the quenching-induced residual stress is compressive at the surface while tensile at the center. Maximum tensile stress of 1029 MPa emerged at the center after the bulk was quenched in oil at 160 °C and the stress reduced to 628 MPa during the subsequent aging. The classical precipitation-strengthening models are utilized to calculate the optimal size of γ′ precipitates (rw) in nickel-based superalloys. After aging treatment, the size of the γ′ precipitates in the bulk sample falls within the optimal precipitate size range. Minimized residual stress and optimized mechanical properties were achieved synergistically via the process optimization. [ABSTRACT FROM AUTHOR]

The dissolution and evolution behavior of oxides in FGH96 superalloys was systematically investigated through the diffusion couples and heat treatment experiments. Results reveal that two distinct interfaces structures were identified at diffusion couple interface of the Ni-based superalloys during heat treatment, namely the contact interface and the oxide particle interface, both exhibiting notable oxygen (O) enrichment. During the heat treatment, the contact interface exhibited a gradual healing process, while the oxide particles were partly dissolute, caused by the decrease of the equilibrium O partial pressure and the diffusion of elements. This results in a reduction of O content at diffusion couple interface to a concentration equivalent to that of matrix. In the diffusion process, a gradient distribution of O concentration was observed from the diffusion couple interface to the matrix, and an apparent O segregation within γ matrix was revealed, indicating a heightened affinity between O and γ matrix. First-principles calculations demonstrated a lower formation energy for O solid solution into Ni (− 5.12 eV) than that into Ni3Al (− 5.00 eV). Additionally, the expansion of the cell parameter was influenced by a higher concentration of O. Consequently, the γ matrix provided a conducive diffusion pathway for O migration from the diffusion couple interface to the matrix. Eventually, O atoms solidly dissolved within γ matrix, leading to the lattice expansion. [ABSTRACT FROM AUTHOR]

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Nickel superalloys are indispensable in industries that demand a fusion of high-temperature mechanical strength and exceptional oxidation resistance, making them ideal for aerospace, power generation, and chemical processing applications. Their versatility extends to various welding applications, including coatings, buttering, and additive manufacturing, where they serve as critical components due to their superior performance characteristics. However, a significant challenge faced by these alloys is hydrogen embrittlement—a phenomenon that can severely compromise their mechanical integrity, leading to catastrophic component failures. This review article synthesizes recent research on hydrogen embrittlement in nickel superalloys, with a focus on understanding the underlying mechanisms that contribute to this phenomenon. It explores how welding processes, including the choice of welding parameters and post-weld treatments, influence the susceptibility to hydrogen uptake and subsequent embrittlement. Furthermore, this review highlights effective strategies for prevention, such as the use of low-hydrogen electrodes, controlled welding environments, and post-weld heat treatments designed to minimize hydrogen diffusion. By addressing these critical aspects, this article aims to provide a comprehensive overview of current challenges and advancements in mitigating hydrogen embrittlement, thereby enhancing the reliability and longevity of nickel superalloy components in demanding industrial applications. [ABSTRACT FROM AUTHOR]

The nickel-based superalloy Inconel is considered suitable for near-net-shape manufacturing using additive techniques, primarily due to its machining difficulties. In laser metal-based powder-bed fusion additive manufacturing, the laser absorptivity of metal powder is one of the parameters that must be known in order to elucidate, optimize, and numerically simulate manufacturing. Therefore, we tried to measure the laser absorptivities of Inconel 718 and Inconel 738LC powders using a commercially available additive manufacturing machine. [ABSTRACT FROM AUTHOR]

Iron–nickel-based superalloy is an ideal substitute for the expensive Inconel 625 and Inconel 751 alloys. To elucidate the evolution of the microstructure and properties of Ni30 alloy under different thermal treatment conditions, a systematic study was conducted on the microstructural transformation of the alloy's strengthening γ′ phase following solution treatment and aging, as well prolonged exposure at 750 °C, and the oxidation behavior of the Ni30 alloy was examined. During prolonged thermal exposure, grain growth occurs mainly in the initial stage, and after 200 h, the prolonged exposure time leads to a significant coarsening of γ′ precipitates, whose area fraction increases by more than 10 times compared to their unaged state. After 100 h of aging, the alloy reaches a peak tensile strength of 1270 MPa and a yield strength of 820 MPa; after 2000 h, the alloy maintains a relatively high strength with a slight decrease in ductility. The oxidation kinetic curve of Ni30 alloy follows the quasi-parabolic oxidation law at 750 °C, and its oxidation rate is consistently lower than 0.1 g·m−2·h−1 throughout the whole oxidation process, which indicates that it has excellent oxidation resistance. The external oxide layer of Ni30 alloy shows a bilayered structure, and no obvious surface porosity or flaking of oxidation products were observed throughout the high-temperature oxidation test. This study not only contributes to the improvement of material properties, but also promotes innovation and development in the field of high-temperature engineering applications that will help to meet the increasingly stringent requirements of high-temperature working environments. [ABSTRACT FROM AUTHOR]

In recent years, there have been important developments in the refractory metal nitride coatings used for versatile applications, such as MoN, TaN, NbN, etc. Engineered approaches, including the deposition method, microstructure control, structural design, and the addition of functional elements, are put into practice for the promotion of coating characteristics. This study focuses on the microstructure and mechanical properties of ternary molybdenum tantalum nitride, MoTaN, coatings. MoTaN was deposited using a reactive radio frequency (r.f.) magnetron co-sputtering system with Mo/Ta target input power modulation control. The effects of composition and microstructure variations on its mechanical properties, including its hardness, elastic modulus, and wear behavior, were investigated. In general, the MoTaN coatings exhibited a columnar polycrystalline microstructure with MoN(111), Mo2N(111), Mo2N(200), TaN(200), and TaN(220) phases and orientations based on X-ray diffraction analysis. The addition of Ta triggered the transition of the primary orientation of Mo2N(111) into Mo2N(200). Transmission electron microscopy was utilized to analyze the transformation of the multiphase structure and changes in the grain size in terms of the Ta addition. According to nanoindentation and wear resistance analyses, superior hardness, elastic modulus, H/E, H3/E2, and wear-resistance values were identified for the MoTaN coatings with 6.8 to 10.4 at.% Ta, and a maximum hardness of 18.0 GPa was found for the MoTaN coating deposited at an input power of Mo/Ta = 150/100 W/W. An optimized hardness of 18.0 GPa and an elastic modulus of 220.7 GPa were obtained. The adjustment of the input power during deposition played a critical role in determining the overall performance of the MoTaN co-sputtering coatings. The MoTaN coating with optimized mechanical properties is attributed to its multiphase microstructure and fine columnar grain size of less than 30 nm. [ABSTRACT FROM AUTHOR]

The effect of Nb on the microstructure evolution of the γ′ phase in Co-Ti-V alloys has been studied. The yield strength and ultimate strength of the alloys are measured via compression at 900 °C. This indicates that the alloys with 1% at. Nb present a dual γ and γ′ microstructure. A Co3V phase exists in 2Nb and 3Nb alloys. The mismatch increases with the increment in Nb content. The yield strength of the alloys rises as the Nb addition increases. After compression at 900 °C, the <101>-type dislocation causes shearing of the γ′ phase in the plane of the base alloy. In the 1Nb alloy, the < 1 1 ¯ 0>-type dislocation reacts at the γ/γ′ interface to generate 1/3<1 2 ¯ 1> super-partial dislocation, and then the γ′ phase is cut by this dislocation and stacking faults are formed. [ABSTRACT FROM AUTHOR]

The post-processing of additively manufactured components is key to optimizing the microstructure of the as-built condition to improve certain mechanical properties. When Alloy 718, a nickel-based superalloy, was manufactured using laser powder bed fusion (LPBF) and subjected to the standard post-processing thermal treatment for wrought Alloy 718, an excessive formation of delta (δ) phase particles, which could compromise the mechanical integrity of the manufactured part, was observed. To address this, both experimental and calculated time–temperature-transformation (TTT) diagrams, along with precipitation kinetics for the formation of δ phase particles, were carefully studied and analyzed to develop a new and effective thermal post-processing treatment. This new heat treatment resulted in a moderate precipitation of δ phase particles. Furthermore, the mechanical property in terms of the microhardness value of AMed Alloy 718 subjected to this new treatment was found to be comparable to that of the wrought material treated with the recommended heat treatment. [ABSTRACT FROM AUTHOR]

Concerns over increasing greenhouse gas emissions have led to growing interest in heat and electricity generation from non-fossil-fuel-based sources, including from advanced nuclear reactors. Among Generation IV nuclear reactor systems, very high temperature reactors (VHTRs) are particularly attractive for producing high-temperature (≥950°C) heat for efficient electricity and hydrogen generation, and for a range of industrial processes. The efficiency (and cost effectiveness) of electricity production by a VHTR, operating with an indirect Brayton power cycle, can be enhanced by raising the temperature of heat transferred through an intermediate heat exchanger (HEX) to a turbine. While compact, printed-circuit-type HEXs are well-suited for such heat transfer, operation at ≥950°C will require VHTR HEXs comprised of new materials with enhanced high-temperature creep resistance and thermal conductivity relative to conventional stainless steels. Ultra-high-temperature, co-continuous zirconium carbide/tungsten (ZrC/W) composites possess an attractive combination of mechanical and thermal properties for high-temperature HEXs. The purpose of this paper is to introduce and demonstrate a scalable, cost-effective, near-net-shape/size process for fabricating thin, dense, co-continuous ZrC/W-based plates with tailorable channel patterns for high-temperature HEXs. Porous rigid WC preform plates with patterned channels were first produced by low-cost pressing/stamping of WC/binder mixtures, followed by binder evaporation and light sintering. The green body binder content, powder bed aspect ratio, and compaction pressure were tailored to produce rigid, porous WC preform plates with desired relative porosity and minimal shrinkage after firing. A continuous thermal treatment was then used to generate a Zr-Cu alloy liquid and for reactive infiltration of this liquid into stationary porous WC preform plates. Such reactive melt infiltration yielded dense, channeled ZrC/W-based composite HEX plates that retained the shapes and dimensions (within a few percent) of the preform plates. By avoiding the need for high pressures and temperatures, for extensive machining/grinding, and for complicated fixturing for melt infiltration, this near net-shape process is a cost-effective, scalable means of producing ZrC/W-based plates with tailorable channel patterns for high-temperature heat exchangers for efficient electricity or hydrogen production by VHTRs or other systems. [Display omitted] • Scalable processing of channeled ZrC/W plates for high-temperature heat exchangers. • Low-cost powder forming/stamping of WC green body plates with tailorable channels. • Rigid, porous, and channeled WC plates upon binder evaporation and light sintering. • Zr-Cu liquid formation and reactive infiltration into porous stationary WC plates. • Dense, thin, co-continuous ZrC/W plates retaining WC plate/channel shapes and sizes. [ABSTRACT FROM AUTHOR]

Ta/Re layered composite material is a high-temperature material composed of the refractory metal tantalum (Ta) as the matrix and high-melting-point, high-strength rhenium (Re) as the reinforcement layer. It holds significant potential for application in aerospace engine nozzles. Developing the Ta/Re potential function is crucial for understanding the diffusion behavior at the Ta/Re interface and elucidating the high-temperature strengthening and toughening mechanism of Ta/Re layered composites. In this paper, the embedded atom method (EAM) potential function for tantalum/rhenium binary alloys (Ta-Re alloys) is derived using the force-matching method and validated through first-principles calculations and experimental characterization. The results show that for the lattice constant of a bcc structure containing 54 atoms, surface formation energies per unit area of Ta-Re alloys obtained based on the potential function are 12.196 Å, E100 = 0.16 × 10−2 eV, E110 = 0.10 × 10−2 eV, and E111 = 0.08 × 10−2 eV, with error values of 0.015 Å, 0.04 × 10−2 eV, 0.02 × 10−2 eV, and 0.01 × 10−2 eV, respectively, compared with the calculations from first principles calculations. It is noteworthy that the errors in the average binding energies of Ta-rich (Ta39Re20, where the number of Ta atoms is 39 and Re atoms is 20) and Re-rich (Ta20Re39, where the number of Ta atoms is 20 and Re atoms is 39) cluster atoms, calculated by the potential function and first-principles methods, are only 1.64% to 1.98%. These results demonstrate the accuracy of the constructed EAM potential function. Based on this, three compositions of Ta-Re alloys (Ta48Re6, Ta30Re24, and Ta6Re48; the numerical subscripts represent the number of atoms of each corresponding element) were randomly synthesized, and a comparative analysis of their bulk moduli was conducted. The results revealed that the experimental values of the bulk modulus showed a decreasing and then an increasing tendency with the calculated values, which indicated that the potential function has a very good generalization ability. This study can provide theoretical guidance for the modulation of Ta/Re laminate composite properties. [ABSTRACT FROM AUTHOR]

By generalizing and transferring the results of the Marcus theory for homogeneous reactions to heterogeneous, Dogonadze and Kuznetsov created a quantum-mechanical theory of electrode reactions for ionic melts, the methodological principles of which allow more adequately evaluating the results of certain experimental methods of obtaining new substances with given properties. Such methods include high-temperature electrochemical synthesis (HES), the implementation of which is complicated by the lack of precise understanding of the mechanism of multi-electron processes of reduction of various ionic forms of refractory metals and nonmetals in ionic melts, including those containing molybdate and tungstate ions, both constantly and simultaneously. [ABSTRACT FROM AUTHOR]

The present research explores theoretical and computational aspects of the morphological instability of Kirkendall voids induced by a directed flux of vacancies. A quantitative phase-field model is coupled with a multi-component diffusion model and CALPHAD-type thermodynamic and kinetic databases to obtain a meso-scale description of Kirkendall void morphologies under isothermal annealing. The material under investigation is a diffusion couple consisting of a multi-phase multi-component single-crystal Ni-based superalloy on one side and pure Ni on the other side. The flux of the fastest diffuser in the superalloy, Al, towards the pure Ni causes a strong flux of vacancies in the opposite direction. This directed flux of vacancies leads to morphologically instable growth of voids. Phase-field simulations are performed in two (2D) and three dimensions (3D) to understand these instabilities, and the results are compared with experimental observations obtained by synchrotron X-ray tomography. Finally, the simulation results are analyzed with respect to the Mullins–Sekerka linear stability criterion. [ABSTRACT FROM AUTHOR]

The effects of aging treatment and the volume fraction of precipitation particles on the nano-hardness and nano-indentation morphology of Ni-based single crystal superalloys are systematically investigated. Using nano-indentation tests and atomic force microscopy (AFM), this study examined the mechanical properties and related physical mechanisms of Ni-based superalloys that have two volume fractions of precipitation particles and four aging treatment times. Results analyzed using the Oliver–Pharr method indicate that prolonging the aging time or increasing the volume fraction of particles enhances the nano-hardness and creep resistance of Ni-based single crystal superalloys and reduces the indentation-affected area. Additionally, the nano-hardness and elastic modulus decrease gradually with increasing applied force, revealing an obvious indentation size effect. These variations are closely linked to the size and density of particles and work hardening rate, as well as to the topologically close-packed (TCP) phases, which influence dislocation movement and accumulation within the material and lead to various nano-indentation behavior in Ni-based single crystal superalloys. The related study provides theoretical guidance and experimental data to support the design and application of superalloys. [ABSTRACT FROM AUTHOR]

The effects of a solution treatment on the microstructure and elevated mechanical properties of the forged Rene 41 superalloy were investigated. The results indicate that the solution treatment temperature has a significant influence on the γ′ structure and mechanical properties. The sub-solvus solution treatment resulted in the co-existence of residual primary coarse γ′ precipitates and fine secondary γ′ precipitates, while the super-solvus solution treatments led to the complete dissolution of the primary γ′ precipitates and the precipitation of a nano-sized secondary spherical γ′ precipitate. The tensile strength increased and then decreased when the solution temperature increased from the sub-solvus to super-solvus solution treatments. In addition, the solution treatment time has a negligible influence on the γ′ and overall mechanical properties due to the complete dissolution of γ′ during the solution treatment at 1080 °C for 1 h. Moreover, the cooling rate following the solution treatment plays a significant role regarding the size and morphology of γ′ and the mechanical properties. The secondary γ′ changed gradually from spherical to concave cubic and octo-cubic and coarsened with the decrease in the cooling rate, resulting in an apparent decrease in strength and increase in ductility. [ABSTRACT FROM AUTHOR]

[Display omitted] • 94% of Cr in SSD exists in stable spinel and some of spinel is wrapped by silicate. • Na 2 S 2 O 8 roasting and acid leaching can achieve the detoxification of SSD. • Under optimized conditions, Cr extraction efficiency could reached up to 80%. • Fe(II) is oxidized to Fe(III) by Na 2 S 2 O 8 , resulting in the collapsing of Cr-spinel. Stainless steel dust (SSD) contains a high content of Cr and is listed as hazardous solid waste. However, SSD is mainly stockpiled in legacy waste sites due to its complexity and lack of investigation. Herein we comprehensively investigates the microscopic interaction between heavy metals and coexisting phases of SSD from the electric arc furnace (EAF). Furthermore, a new approach for extracting Cr from SSD was developed for the first time. It was found that SSD is enriched with Cr, Ni, Mn, and Zn. Most of these heavy metals are bound to stable spinel (e.g., FeCr 2 O 4) and encapsulated by silicate. Using Na 2 S 2 O 8 as the flux (1–24 mmol), under roasting at 350–750 °C in the air for 0.25–6 h, efficient heavy metal extraction can be achieved (Cr-80 %, Ni-86 %, Mn-93 %, Zn-94 %) at 650 °C for 1h. During the roasting processes, the silicate shell was broken, which facilitated the mass transfer of the oxidant. Fe(II) was oxidized to Fe(III) and collapsed the spinel structure, releasing the heavy metals during the following acid leaching. The total mass of SSD is reduced by 90–95 %, and detoxification of SSD is achieved after processing. In conclusion, efficient extraction refractory metals in SSD by Na 2 S 2 O 8 roasting and the mechanism was elucidated for the first time. This method might also be applied for the treatment of other slags/ash waste that have a stable spinel structure and are encapsulated by silicate. [ABSTRACT FROM AUTHOR]

The present study assessed the compression performance of four strut lattices manufactured via laser powder bed fusion (LPBF), namely selective laser melting (SLM) from Inconel 625 and Ti-6Al-4V. Static finite element analysis and mechanical testing were performed, and it was concluded that the experimentally determined performance trend was in good agreement with that obtained by numerical methods. The cell type greatly influences the compressive performance of the lattices, regardless of the material used for manufacturing. The best compressive performances were recorded for the octet lattice, followed by the truncated octahedron, Kelvin, and re-entrant lattices. Regarding material performance, for the first maximum compressive strength, similar results were recorded for both materials; a difference was recorded in the case of yield strength, with higher values were recorded for Ti-6Al-4V compared to Inconel 625. The average first maximum compressive strength for the Ti-6Al-4V lattice was between 30.39 and 290.17 MPa, and it was within a range of 16.22–258.71 MPa for Inconel 625. The elastic modulus was between 1.74 and 4.72 GPa for Ti-6Al-4V, and 1.13 and 4.46 GPa for Inconel 625. A more ductile behavior was registered for the nickel-based superalloy than for the titanium alloy; the Inconel 625 specimens were characterized by a bending-dominant damage mode, and Ti-6Al-4V specimens were characterized more by a stretch-dominant damage mode. [ABSTRACT FROM AUTHOR]

A long-standing problem in the study of the under-hole-doped cuprates has been the description of the Fermi surfaces underlying the high magnetic field quantum oscillations, and their connection to the higher temperature pseudogap metal. Harrison and Sebastian [Phys. Rev. Lett. 106, 226402 (2011)] proposed that the pseudogap "Fermi arcs" are reconstructed into an electron pocket by field-induced charge density wave order. But computations on such a model [Zhang and Mei, Europhys. Lett. 114, 47008 (2016)] show an unobserved additional oscillation frequency from a Fermi surface arising from the backsides of the hole pockets completing the Fermi arcs. We describe a transition from a fractionalized Fermi liquid (FL*) model of the pseudogap metal, to a metal with bidirectional charge density wave order without fractionalization. We show that the confinement of the fermionic spinon excitations of the FL* across this transition can eliminate the unobserved oscillation frequency. [ABSTRACT FROM AUTHOR]

Refractory metal oxides such as titanium dioxide (TiO 2), tantalum oxide (Ta 2 O 5), and niobium oxide (Nb 2 O 5) coated-titanium and its alloys for medical applications have recently gained significant attention due to their remarkable properties, including high hardness, strong chemical inertness, and excellent biocompatibility. However, comparative studies among them remain scarce. In this study, thin films of Ta 2 O 5 , Nb 2 O 5 , and TiO 2 were deposited on Ti6Al4V titanium alloy using radio frequency sputtering technology. Their properties were comparably evaluated through a series of tests, including scratching, nanoindentation, friction and wear, potentiodynamic polarization, and cell cultivation experiments. The results revealed that all three coatings, with a thickness of approximately 2.6–2.8 μm, exhibited an amorphous columnar growth pattern with dense surfaces resembling cauliflower. The bonding force of the TiO 2 coating exceeds 50 N, which is 26.2 times and 14.5 times greater than that of Ta 2 O 5 and Nb 2 O 5 , respectively. Furthermore, all coated samples demonstrate superior wear resistance, corrosion resistance, and biocompatibility compared to bare Ti6Al4V. Among the coatings, TiO 2 showed the best performance, followed by Ta 2 O 5 , while Nb 2 O 5 exhibited the least favorable performance. These findings revealed the performance differences among the three ceramic coatings on Ti6Al4V samples and offer valuable insights for further research and the selection of coatings to enhance the properties of Ti6Al4V titanium alloy for biomedical applications. [ABSTRACT FROM AUTHOR]

Herein, the hot deformation behavior and microstructure evolution of N06625 superalloy are studied. Hot deformation behavior at 950–1200 °C and strain rate 0.1–10 s−1 are carried out by Gleeble‐3800 thermal simulator machine. The activation energy (Q) of the alloy is calculated by the change of stress–strain curve. The microstructure of the experimental material is characterized by electron backscatter diffraction, and it is found that the recrystallization fraction rate increases with the increase of temperature, but decreases first and then increases with the increase of strain rate. Discontinuous dynamic recrystallization is the main nucleation mechanism of N06625 superalloy. Continuous dynamic recrystallization (CDRX) is the auxiliary nucleation mechanism; CDRX gradually decreases with the increase of temperature. In addition, it is found that the evolution of special boundaries is closely related to the strain rate. The longer deformation time is beneficial to the interaction of grain boundaries, which leads to the special boundary fraction, and the increase of special boundary fraction can effectively weaken the preferred orientation caused by recrystallization growth. [ABSTRACT FROM AUTHOR]

Aluminide coatings were prepared by chemical vapor deposition (CVD) method on Ni-based superalloy Mar-M247 to improve the corrosion resistance. The Na2SO4-induced hot corrosion behavior of Mar-M247 with and without aluminide coating was investigated at varying temperatures. The results revealed that the substrate underwent relatively mild corrosion attack at temperatures below the Na2SO4 melting point, but extremely severe corrosion attack above it. The aluminide coating significantly improved the corrosion resistance of the substrate, with the formation of Al2O3 scale during corrosion. The effects of both solid and molten Na2SO4 on hot corrosion resistance of Mar-M247 alloy and its aluminide coating was discussed, as well as the detrimental effect of tungsten on the substrate in 'type I' hot corrosion. [ABSTRACT FROM AUTHOR]

Deep eutectic electrolytes (DEE) have emerged as an innovative approach to address the instability and safety issues of lithium metal batteries at elevated temperatures. However, in practice, there is often an undesirable incompatibility between the eutectic mixture and electrodes, and also an insufficient reduction stability of DEE due to the increased Li+ concentration. Herein, we designed a new DEE by utilizing weakly solvating tetrahydropyran (THP) solvent. Due to the high reduction resistance of THP and concentrated lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), this DEE demonstrates enhanced compatibility with Li metal anode and high temperature tolerance with LiMn2O4 cathode. The Li||LiMn2O4 cell (1.6 mAh cm−2) shows a high capacity retention of 96.02 % after 600 cycles at room temperature. More importantly, this Li||LiMn2O4 cell achieves a remarkable high‐temperature performance with a high capacity retention of 91.72 % after 120 cycles and low self‐discharge after storage for 240 hours at a high temperature of 55 °C, which is critical for LiMn2O4 cathode. Overall, this electrolyte design provides an alternative pathway for the development of DEEs for high‐temperature and high‐voltage lithium metal batteries, which can also be expanded to other batteries. [ABSTRACT FROM AUTHOR]

The results of studies on the influence of the modes of shielded arc welding with a non-consumable electrode on the mechanical properties of parts manufactured from EK-61 powder alloy by direct laser deposition are presented. The results of metallographic studies of the weld and heat-affected zone are described. The possibility of obtaining high-quality welds using shielded arc welding of such products is shown. The influence of the number of passes on the quality of the weld is noted. [ABSTRACT FROM AUTHOR]

Wire-feed additive manufacturing (WFAM) produces superalloys with complex thermal cycles and unique microstructures, often requiring optimized heat treatments. To address this challenge, we present a hybrid approach that combines high-throughput experiments, precipitation simulation, and machine learning to design effective aging conditions for the WFAM Haynes 282 superalloy. Our results demonstrate that the γ' radius is the critical microstructural feature for strengthening Haynes 282 during post-heat treatment compared with the matrix composition and γ' volume fraction. New aging conditions at 770°C for 50 hours and 730°C for 200 hours were discovered based on the machine learning model and were applied to enhance yield strength, bringing it on par with the wrought counterpart. This approach has significant implications for future AM alloy production, enabling more efficient and effective heat treatment design to achieve desired properties. IMPACT STATEMENT: Our research tackles suboptimal properties in additively manufactured alloys with conventional heat treatment, using high-throughput experiments, CALPHAD (CALculation of PHAse Diagrams), and interpretable machine learning to effectively optimize heat treatments for WFAM (Wire-Feed Additive Manufacturing) Haynes 282 superalloy. [ABSTRACT FROM AUTHOR]

Heat treatments and oxidation tests were performed on systems composed of a single-crystal AM3 superalloy with a NiCoCrAlYTa+Pt coating to investigate the effect of Pt on Ta and Ti diffusion at high temperature. Experimental results were compared to an AM3 superalloy directly coated with Pt. For all the studied systems, the effect of Pt on elemental activities was evaluated through thermodynamic calculations. Pt diffusion was found to be faster in the NiCoCrAlYTa coating than in AM3. High Ta contents were measured in the Pt-rich γ′ phase below the surface and significant Al and Cr transport toward the surface was observed, in agreement with thermodynamic calculations which predicted an important decrease in their activities in the presence of Pt. An outward diffusion of Ti was also noticed, whereas calculations did not show a decrease in Ti activity due to Pt. Other discrepancies between experiments and thermodynamic calculations were noted and are discussed in this work. [ABSTRACT FROM AUTHOR]

This paper highlights that hot corrosion at 750 °C can develop on the surface of AM1 nickel-based single-crystal superalloy (SX) turbine blades, whether in the As-Cast (AC) or Fully Heat-Treated (FHT) states even in the absence of SO3 (g) flow. It was found that the 1 and 3 mg/cm2 Na2SO4 deposits induce sulphidation, oxidation and basic flux at such low temperature like in Type I hot corrosion. Sulphidation is mainly located in the γˈ-depleted zone irrespective the substrate (AC and FHT). The metallurgical segregations in the AC superalloy extend the incubation period in contrast to what is observed upon pure oxidation. The increase in salt content showed a reduction in hot corrosive attack by forming a barrier layer. [ABSTRACT FROM AUTHOR]

Ni-Cu alloys are promising for application at temperatures between 400–900 °C and reducing atmospheres with high C-contents. Typically, under such conditions, metallic materials in contact with the C-rich atmosphere are degraded by a mechanism called metal dusting (MD). Ni-Cu-alloys do not form protective oxide scales, but their resistance is attributed to Cu, which catalytically inhibits the C-deposition on the surface. Adding other alloying elements, such as Mn or Fe, was found to enhance the MD attack of Ni-Cu alloys again. In this study, the effect of the Mn and Fe is divided into two affected areas: the surface and the bulk. The MD attack on binary Ni-Cu alloys, model alloys with Fe and Mn additions, and commercial Monel Alloy 400 is experimentally demonstrated. The surface electronic structure causing the adsorption and dissociation of C-containing molecules is investigated for model alloys. Analytical methods such as scanning electron microscopy combined with energy-dispersive X-ray spectroscopy, electron probe microanalysis combined with wavelength-dispersive X-ray spectroscopy, X-ray diffraction analysis, and near-edge X-ray absorption fine structure measurements were used. The results are correlated to CALPHAD calculations and atomistic simulations combining density functional theory calculations and machine learning. It is found that the Cu content plays a significant role in the surface reaction. The effect of Mn and Fe is mainly attributed to oxide formation. A mechanism explaining the enhanced attack by adding both Fe and Mn is proposed. [ABSTRACT FROM AUTHOR]

The combination of cold deformation and solution aging is an important technological route for the bar processing of superalloy fasteners. The microstructure evolution and mechanical properties are intimately related to the process parameters. In this study, we systematically elucidate the mechanical properties and microstructure evolution of Fe-15Cr-25Ni alloys in different treatment processes and conduct in-depth analysis of the synergistic strengthening mechanism of fine-crystal strengthening, second-phase strengthening, and work hardening on Fe-15Cr-25Ni alloys. The results show that the tensile strength and yield strength at room temperature increase with the increase in grain refinement and dislocation density but decrease with the increase in elongation. After solid-solution treatment, most of the precipitates dissolve into the matrix, and the dislocation density is greatly reduced, resulting in a decrease in strength and an increase in plasticity. After aging, a large amount of γ′ phase was precipitated. Due to the two strengthening effects of dislocation strengthening and second-phase strengthening, the strength of the aging state is more improved than that of the cold-drawing state. The purpose of this study is to provide valuable insights for the industrial production of Fe-15Cr-25Ni superalloys. [ABSTRACT FROM AUTHOR]

This work investigates the piercing of microholes in turbine shroud rings (Inconel-625) using the Abrasive Waterjet Cutting process. The concern with the hole piercing is the kerf angle caused by the attenuation of the jet energy and stand-off distance, which seriously impacts the processing precision of abrasive water jet piercing. The effects of piercing parameters like machining time (40, 60 and 80 s), abrasive mesh size (80 mesh and 120 mesh), stand-off distance (1, 2, 3 and 4 mm), abrasive jet pressure (100, 125, 150 and 175 MPa) are studied to reduce the kerf angle. The kerf angle increased linearly with a stand-off distance increase at different machining times. By piercing for 60 s and 80 s, the lowest values of kerf angle are obtained (0.03∘ and 0.02∘). The optimum conditions for making a pierced hole with a minimum kerf angle of 0.02∘ were achieved with a machining time- of 60 s, abrasive mesh size- of 20 mesh, and abrasive jet pressure- of Scanning electron microscope (SEM) images and visual measuring system (VMS) images are used to identify the surface characteristics in kerf zone. The features, including ploughing, particle embedment, lip impression and wear path due to the ductile mode of erosion caused by high energy impact, is also discussed. [ABSTRACT FROM AUTHOR]

Gas turbine superalloys experience hot corrosion, driven by factors including corrosive deposit flux, temperature, gas composition, and component material. The full mechanism still needs clarification and research often focuses on laboratory work. As such, there is interest in causal discovery to confirm the significance of factors and identify potential missing causal relationships or codependencies between these factors. The causal discovery algorithm fast causal inference (FCI) has been trialled on a small set of laboratory data, with the outputs evaluated for their significance to corrosion propagation, and compared to existing mechanistic understanding. FCI identified salt deposition flux as the most influential corrosion variable for this limited data set. However, HCl was the second most influential for pitting regions, compared to temperature for more uniformly corroding regions. Thus, FCI generated causal links aligned with literature from a randomised corrosion data set, while also identifying the presence of two different degradation modes in operation. [ABSTRACT FROM AUTHOR]

Co‐based γ/γ′ superalloys are in development as candidates to replace Ni‐based superalloys in turbine engines, where they will be exposed to hot corrosion. The present study investigates the resistance to high temperature Type I hot corrosion of four alloys of the Co–Ni–Al–W system, which differed in their Co to Ni ratio and their W content. In addition, the alloys are tested not only uncoated but also with an Al and a Cr diffusion coating. The exposures were performed at 950°C with a Na2SO4 deposit of 2.5 mg/cm2 in air containing 0.1% SO2 for 100 and 300 h. The degradation was investigated by material loss measurements. Both coatings proved mostly protective for 100 h, while the uncoated samples were severely degraded. After the longer exposure time, only the Cr‐coating remained partially protective and outmatched the Al‐coating. Further, a positive influence was attributed to a higher Co to Ni ratio (1.4 vs. 0.7) and a higher W content (5 vs. 3 at%). [ABSTRACT FROM AUTHOR]