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Extensive experimental and computational studies have demonstrated outstanding physical and chemical properties of the novel materials of compositionally complex carbides (CCCs), enabling their promising applications in advanced fission and fusion energy systems. This perspective provides a comprehensive overview of radiation damage behavior reported in the literature to understand the fundamental mechanisms related to the impact of multi-principal metal components on phase stability, irradiation-induced defect clusters, irradiation hardening, and thermal conductivity of compositionally complex carbides. Several future research directions are recommended to critically evaluate the feasibility of designing and developing new ceramic materials for extreme environments using the transformative "multi-principal component" concept. Compared to the existing materials for nuclear applications including stainless steels, nickel alloys, ZrC, SiC, and potentially high-entropy alloys, as well as certain other compositionally complex ceramic families. CCCs appear to be more resistant to amorphization, growth of irradiation defect clusters, and void swelling. [ABSTRACT FROM AUTHOR]

The creep mechanism of a Co-based single-crystal (SX) superalloy at 760°C/800 MPa (∼90% yield strength) was revealed and differed from those of Re-containing Ni-based SX superalloys. Experimental alloy displays superior creep resistance in the early creep stage, likely due to the accumulation of matrix dislocations and W segregation-assisted shearing of γ′ phase by leading Shockley partial dislocations instead of Co and Cr segregation a < 112> SF ribbons in Re-containing Ni-based SX superalloys during the accelerating creep stage. Segregation-assisted local χ/η phase transformations at SFs stabilize and enhance SF interactions, contributing to the subsequent slow accelerating creep stage. [ABSTRACT FROM AUTHOR]

The aim of this research is to investigate the influence of nickel alloy type from the same group, the parameters of flame spraying, as well as the preparation of the substrate and the heat treatments of the substrate on the microstructure of the coating/substrate system. Due to the possibility of applying nickel alloys in corrective maintenance of tools used on elevated working temperatures, hot work tool steel X38CrMoV5-1 was selected as a substrate material. The investigation of the microstructure of the coating/substrate system was carried out according to the factorial design of experiment, where the input factors were varied on two levels. The factors that were varied are: Ni-based self-fluxing alloys - NiCrBSi and NiBSi; distance of the burner from the workpiece - small (6 mm) and large (20 mm); preparation of the substrate - roughened and non-roughened and the heat treatments of the substrate - soft annealed and tempered condition. Ni-based self-fluxing alloys were applied on samples (12,5 × 25 × 25 mm) by flame spraying with simultaneous fusing process. Analysis of the microstructures of the coating/substrate system was carried out on the Leica DM 2500M light microscope. After the conducted analysis the paper concluded that by spraying the selected coatings onto the X38CrMoV5-1 tool steel base, poor quality coatings are obtained, due to the appearance of cracks (NiCrBSi) or separation of the coating from the substrate (NiBSi). This is attributed to the formation of martensitic structure of the substrate after spraying and the presence of residual stresses. [ABSTRACT FROM AUTHOR]

AbstractThis study explores the dissimilar welding of nickel superalloy 59 with Fe-Ni superalloy 904 L using the Gas Tungsten Arc Welding with Hot Wire technique (HW-GTAW). The HW-GTAW process produced defect-free weldments with complete penetration, as confirmed by macroscopic analysis. Microstructural analysis using FESEM and EDS revealed fine equiaxed and columnar dendrites in the fusion zone and identified a secondary phase enriched with chromium. XRD analysis supported the presence of predominant austenitic phases and indicated the formation of Cr23C6-type carbide. The grain size of the weld joint, determined using the Gaussian method and Scherer formula, was 44.53 nm, slightly smaller than base metals. Microhardness tests revealed values ranging from 226 ± 5 HV 10 to 243 ± 5 HV 10, with the highest values observed in the deep cryogenic treatment (DCT). The Mo in the ERNiCrMo-13 filler and the effects of DCT, which promote grain refinement, are responsible for this increase in hardness. Residual stress measurements revealed a maximum tensile stress of 315 MPa along the longitudinal axis and a maximum compressive stress of 355 MPa along the transverse axis. DCT enhanced the weldment’s tensile strength by up to 12% compared to as-welded samples, with a 6% increase compared to shallow cryogenic-treated (SCT) samples. Charpy impact testing indicated a value of 88 J in the fusion zone, which is 1.2% less than alloy 59 and 9% higher than 904 L. Tensile fracture analysis revealed ductile dimples, while impact fractography showed a mix of ductile dimples and brittle, glassy cleavage facets. [ABSTRACT FROM AUTHOR]

The sluggish kinetics of alkaline hydrogen evolution reaction (HER) hinders practical exploitation of water splitting. Catalysts, known as platinum single atoms (Pt‐SAs) anchored in Ni4Mo/Ni alloys on nickel foam (Pt SAs‐Ni4Mo/Ni@NF) with ultralow Pt mass loading (mPt = 0.3 wt.%) derived from self‐reconstruction, with boosted atomic utilization in alkaline HER are demonstrated. In situ characterizations confirm the leaching of Mo species during the self‐reconstruction of NiMoO4, which facilitates the anchoring of Pt‐SAs through the generation of atomic defects. Further, density functional theory (DFT) calculations indicate that the atomic defects can effectively capture Pt2+ in salt solution, aiding in the distribution of Pt‐SAs. Besides, theoretical results emphasize that Pt SAs‐Ni4Mo/Ni with unique Pt‐Ni interaction can accelerate the desorption of hydroxides in alkaline electrolytes during HER, as well as lower energy barriers for reaction steps. Pt SAs‐Ni4Mo/Ni@NF shows remarkable catalytic activity toward alkaline HER with a low overpotential of 17 mV (j = 10 mA cm−2), together with high atomic utilization of Pt (8.92 A mgPt−1 at 30 mV) and excellent durability. This work not only provides a scalable preparation for efficient and robust low‐Pt catalysts but also establishes in‐depth understanding of the synergistic interaction between Pt SAs and Ni‐Mo alloys in alkaline HER, which is likely to accelerate the development of water‐splitting technique. [ABSTRACT FROM AUTHOR]

In a two-step reduction process, Ni-based alloy nanocatalysts (Ni-ANCs) made of nickel-iron-cobalt with a carbon support (Ni–Fe–Co/C) were produced in various molar proportions. A comprehensive structural characterization of the morphology and composition of Ni-ANCs was evaluated using XRD, TEM and EDX analyses. The XRD results from Ni-ANCs indicated a diffraction pattern that was caused by only one face-centered cubic (FCC) phase, indicating that the ternary metals Instead of a phase-separated structure, a well-mixed solid solution structure was created. TEM images showed that Ni-ANCs have a particle size of between 13 and 30 nm uniform dispersivity on the carbon support. At the same time, the electrochemical activities of Ni-ANCs were evaluated by means of CV, LSV and CA investigate for the Induction of electrooxidation in ethylene glycol at room temperature. Experimental results reveal that Ni 60 Co 40 /C and Ni 60 Fe 30 Co 10 /C are substantially more potent than Ni 60 Fe 40 /C and Ni 100 /C respectively, when using Co-containing alloy nanocatalysts. Specifically, the ternary Ni 60 Fe 30 Co 10 /C catalyst has a higher electrochemical activity than its binary counterpart, which can be attributed to the conductivity and deformation effects. This is noteworthy because it demonstrates that Co accelerates the oxidation of Ni to a more active NiOOH at a lower overpotential level, enabling otherwise inactive Fe sites within the Ni (OH) 2 phase to become active. A Micro flow channel with distinct zones and its structure and cross-section for the MLEGFC [Display omitted] • The structural characterization of the morphology and composition of Ni-ANCs was evaluated using XRD, TEM and EDX analyses. • TEM images showed that Ni-ANCs have a particle size of between 13 and 30 nm. • A greater activity of Ni 60 Fe 30 Co 10 /C can be observed than Ni 60 Co 40 /C and Ni 60 Fe 40 /C, however, Ni 100 /C is lower. [ABSTRACT FROM AUTHOR]

In this investigation, the growth behavior of a crack in a nickel-based superalloy under a turbine standard load sequence was determined by experimental, analytical, and computational methods. In the first experimental approach, ASTM standard compact tension (CT) test specimens were fabricated and fatigue crack growth (FCG) tests were conducted in a universal test machine under cold-TURBISTAN, a turbine standard spectrum load sequence. In the second analytical method, after rain-flow cycle counting of the cold-TURBISTAN sequence, the crack growth was estimated for each counted cycle from the crack growth law. The accumulated crack extension for each block of loading was thus estimated to determine the FCG behavior. In the third computational approach, a CT specimen containing an initial crack was modeled and the FCG behavior was predicted under cold-TURBISTAN spectrum load sequence using FRANC3D. The FCG trend predicted by analytical and computational methods was almost similar to the observed experimental behavior. The predicted FCG life was conservative with a life ratio ranging from 0.9 to 0.95. [ABSTRACT FROM AUTHOR]

The aim of this study was to develop a new manufacturing process for bimetallic materials by combining laser treatment with traditional casting methods. This process involves laser-treating nickel alloy-grade UNS 6230 plates to create a regular macro-relief on their surface. These treated plates are then placed in a sand mold, and molten non-alloy steel (S235JRG2) is poured into the mold to create bimetallic layered castings. The experimental procedure focuses on optimizing the melt-to-solid phase ratios and pouring temperatures to achieve a uniform microstructure and strong mechanical properties in the bimetals. The produced bimetallic castings are suitable for applications in the oil refining and chemical industries and heavy machinery sector. The quantitative results indicate that the optimized process parameters lead to a high-quality transition zone with minimal defects, characterized by the diffusion of alloying elements from the nickel alloy to the steel. The microstructure, chemical, and phase compositions were evaluated using XRD and SEM with EDS, confirming the formation of a robust metallurgical bond. Key findings include a significant improvement in the hardness and strength of the transition layer, with the optimal pouring temperature being 1600 °C. The resulting bimetallic materials demonstrate an improved performance in demanding industrial environments. [ABSTRACT FROM AUTHOR]

This work elucidates the interactions between Re and hydrogen at γ/γ′ interfaces, enhancing the hydrogen-embrittlement resistance of nickel-based single-crystal superalloy (Ni-SX). The H-charged Ni-SX exhibits severe embrittlement characterized by the appearance of parallel dislocation slip bands and micro-cracks, which could be effectively mitigated through improving the Re content. The segregation behaviors of hydrogen at γ/γ′ interfaces, as captured by hydrogen microprint technique, significantly diminish interfacial cohesion strength by reducing the local atomic bonding strength. Detailed characterizations of bonding charge density highlight that Re plays a crucial role in reducing hydrogen embrittlement susceptibility by suppressing the hydrogen-induced degradation of bonding strength. The role of Re on hydrogen-embrittlement resistance of superalloys is investigated through tensile tests and first-principles calculations, revealing the suppressive effect of Re on hydrogen-induced decohesion behaviors at γ/γ′ interface. [ABSTRACT FROM AUTHOR]

Hot corrosion of Ni-based superalloys has been extensively studied due to its negative impact on aero-turbine engines. However, the complexity of hot corrosion makes it difficult to discern the degradation pathways of field-exposed parts. To that end, it is technically important to conduct more complex laboratory-scale testing to develop a better understanding of the degradation pathways that may affect a field-exposed part. Na2SO4 has been the principal deposit considered in past studies, but with little consideration given to another common environmental species, NaCl. This study aimed to better understand the role of NaCl in Na2SO4 deposits at 900°C on a 2nd-generation, Ni-based superalloy, PWA 1429. A NaCl-only deposit was also studied to isolate NaCl's role in affecting degradation. It was found that additions of NaCl induced greater degradation when compared to a Na2SO4-only deposit. Short-term exposures were able to determine that NaCl forms volatile chlorides with nickel that subsequently oxidize to form a porous, non-protective product. In tandem, oxygen ingress causes subsurface aluminum oxidation, which inhibits the formation of a protective oxide on the alloy. The results indicate that NaCl plays a major role early in the degradation process which may be missed during post-analyses after long-term exposures. [ABSTRACT FROM AUTHOR]

The development of silicon (Si) photoanodes for photoelectrochemical (PEC) oxidation is highly crucial for the progress of solar‐driven hydrogen production. Apart from the typical water oxidation reaction or oxygen evolution reaction (OER), the urea oxidation reaction (UOR) is gaining more attention due to favorable thermodynamics. In this work, we study Si photoanodes modified with electrodeposited copper‐nickel (CuNi) alloy for OER and UOR. The optimized photoanodes exhibit a low onset potential of 1.15 V vs reversible hydrogen electrode (RHE) and a current density of 6 mA cm−2 at 1.23 V vs RHE (the thermodynamic potential for water oxidation) for OER. Further, CuNi alloy‐modified photoanodes can drive the UOR at a lower onset potential (1.05 V vs RHE) and generate a higher current density of 31 mA cm−2 at 1.23 V vs RHE. Importantly, the CuNi alloy can extend the stability for UOR under PEC conditions when compared to a planar Ni film deposited by a vacuum‐based process. This work demonstrates that CuNi alloy can further improve the properties of inhomogeneous metal‐insulator‐semiconductor Si photoanodes which can be efficiently utilized for both OER and UOR. [ABSTRACT FROM AUTHOR]

In this paper, 20 µm and 40 µm thick aluminide coatings were deposited on MAR-M247 nickel-based superalloy through the chemical vapor deposition (CVD) process in a hydrogen protective atmosphere for 4 h and 12 h, respectively, at a temperature of 1040 °C and an internal pressure of 150 mbar. The effect of aluminide coating thickness on the high-temperature performance of the MAR-M247 nickel-based superalloy was examined during a fatigue test at 900 °C. After high-temperature testing, the specimens were subjected to fractographic analysis to reveal the damage mechanisms. No significant effect of coating thickness was found since the material exhibited a similar service life throughout the fatigue test when subjected to the same stress amplitude. One should stress that the coating remained well adhered after specimen fracture, confirming its effectiveness in protecting the material against high-temperature oxidation. [ABSTRACT FROM AUTHOR]

This study aims to investigate the effects of different catalysts on biomass gasification. Therefore, red mud (RM) and Aluminum–Nickel alloy were used as catalysts with biomass mixture (BM) for the lab-scale gasification studies by using an updraft and a modifiable-downdraft fixed bed reactor. The maximum volumetric percentage of H 2 , ranging from 51% to 65%, was achieved at 900 °C in both gasifiers. Al–Ni catalyst significantly boosted H 2 content, reaching 65% in the updraft gasifier at 900 °C with 0.05 L/min dry air. H 2 /CO ratio varied from 2 to 4 for BM, while catalyst use expanded the range to 1.6–7 with the Al–Ni catalyst demonstrating the most effective performance. In general, it was seen that RM increased the H 2 component in the syngas between 1 and 7 vol% at 900 °C in updraft gasifier. In the modifiable-downdraft reactor, on the contrary, H 2 concentration in the syngas decreased by 2–6% with the addition of RM. [Display omitted] • Red mud and aluminum - nickel alloy were added to biomass as catalysts. • Two different fixed-bed gasifiers were operated under the same conditions. • The use of the catalyst increased the H 2 vol% in the syngas. • The max. volumetric percentage of H 2 gas was found to be in the range of 51–65%. [ABSTRACT FROM AUTHOR]

In order to evaluate the abrasive belt grinding performance, this paper proposes to conduct nickel-based superalloy robot abrasive belt grinding experiment based on different types of abrasive belts with multiple grit sizes. First, the single grinding performance evaluation is performed through five performance parameters: material removal rate, surface roughness, tangential force, specific grinding energy, and specific wear height. Then, based on the evaluation results of single grinding performance, a weighted evaluation function is established to comprehensively evaluate the grinding performance. It is found that the structured abrasive belt has relatively better grinding performance. The main factors affecting the abrasive belt grinding performance are identified through the evaluation results, with the effect of grit size being more significant. In addition, this paper analyzes the characteristics of material deformation based on the grinding subsurface microstructure, and discusses the effects of abrasive belts on material deformation. [ABSTRACT FROM AUTHOR]

Large-scale nonequilibrium molecular dynamics simulation is used to study the effect of grain size and Cr segregation at the twin boundary (TB) on the spalling fracture mechanism of nickel based alloys. In particular, loading waves are designed so that the maximum tensile stress first appears in the grain interior for all the crystals with different grain sizes. In contrast to traditional understandings, no monotonous relationship between the spall strength and the grain size appears in our results. The spall strength is found to depend on the wave attenuation distance measured from the first maximum tensile stress position to the spalled TB as well as the accompanied microstructure evolutions. The number of spalling plane increases with the increase of TB or the decrease of the grain size. As the grain size continues to decrease, a greater impact strength is required to cause spallation fracture at multiple TBs. In this case, the spall strength becomes insensitive to the first maximum tensile stress position. With the increment of solute atom concentration, the number of the spalling plane increases when the solution is segregated. But it decreases when the solution is uniformly distributed. Such a result is explained by segregation-enhanced energy dissipation and interactions between the waves and the microstructures nearby TBs. In particular, the shock wave would induce a local lattice reorientation nearby the TB depending on its segregation degree and the lattice reorientation would modify the slip manner of stacking faults and, thus, affect void nucleation and growth. The lattice reorientation would also contribute to the generation of sub-grain boundaries inside the grains in terms of the movement of stacking faults. Void nucleation at the sub-GB is the main cause of fracture at the grain interior. [ABSTRACT FROM AUTHOR]

Surface grinding is a widely employed finishing process in industrial sectors dedicated to achieve desired Surface characteristics of components. This study experimentally investigates the impact of the grinding parameters pertaining to the surface characteristics of Inconel 800, which is a nickel-iron-chromium alloy extensively used in high-temperature applications. Various commercially available grinding wheels were employed to grind Inconel800 under different grinding conditions. The ground surfaces were comprehensively analyzed using surface roughness measurements, Three-dimensional profilometry, optical microscopy, findings from XRD and SEM reveal that grinding parameters and wheel characteristics significantly impact the surface texture, topographical features, residual stress, and surface morphology of the machined nickel alloy.. The insights from this investigation contribute to the understanding of the grinding behavior of nickel-based superalloys and provide a basis for optimizing the grinding process for enhanced surface integrity. The findings are valuable for industries dealing with the machining of high-performance nickel alloy components. [ABSTRACT FROM AUTHOR]

Formation and growth of secondary γ′ precipitate-free zones (PFZ) in the vicinity of grain boundaries in five Ni-based superalloys have been investigated for different heat treatment times and temperatures. A special focus has been placed on a high carbon containing version of the AD730™ alloy. While the formation of PFZ is induced by the precipitation of Ti-rich secondary carbides during aging in Nimonic PE16, it has been shown in the present study that PFZ mainly form during close-to-γ′-solvus heat treatments and are associated with the nucleation of intergranular γ′ precipitates in the studied alloys. Since these precipitates have chemical compositions similar to intragranular secondary γ′ particles, depletion of precipitate-forming elements leads to the dissolution of intragranular secondary γ′ precipitates near grain boundaries and finally to the formation of PFZ. PFZ width evolutions have been described using a parabolic model, and their kinetics obey an Arrhenius-type law indicating a diffusion-controlled process. Thanks to chemical composition analyzes in and near the PFZ, it is shown that both titanium and niobium diffusion, in volume and through the grain boundaries, could be controlling the PFZ formation. [ABSTRACT FROM AUTHOR]

Ni-base superalloys operate in harsh service conditions where cyclic heating and cooling introduce deformation fields that need to be investigated in detail. We used the high-angular-resolution electron backscatter diffraction method to study the evolution of internal stress fields and dislocation density distributions in carbides, dendrites, and notch tips. The results indicate that the stress concentrations decay exponentially away from the notch, and this pattern of distribution was modified by the growth of cracks and the emission of dislocations from the crack tip. Crack initiation follows crystallographic traces and is weakly correlated with carbides and dendrites. Thermal cycles introduce local plasticity around carbides, the dendrite boundary, and cracks. The dislocations lead to higher local stored energy than the critical value that is often cited to induce recrystallization. No large-scale onset of recrystallization was detected, possibly due to the mild temperature (800 °C); however, numerous recrystallized grains were detected in carbides after 50 and 80 cycles. The results call for a detailed investigation of the microstructure-related, thermally assisted recrystallization phenomenon and may assist in the microstructure control and cooling channel design of turbine blades. [ABSTRACT FROM AUTHOR]

The study aims to analyze the tensile behavior and microstructural changes in MAR‐M247 nickel‐based superalloy across different temperatures. Tensile behavior is examined under a constant strain rate of 2.5 × 10−4 s−1 at varying temperatures. Results indicate a temperature‐dependent nature of the alloy's tensile properties. At 550 °C, a Portevin–Le Chatelier effect is observed, attributed to twinning nucleation and carbon atom diffusion. Dynamic recrystallization occurs at 950 °C, manifesting in a sinusoidal stress–strain curve. At room temperature, the primary fracture mechanism involves dislocation shearing in the γ matrix, with minor dislocation shearing in the γ′ phase. At 550 °C, carbides along grain boundaries and the γ′ phase impede dislocation motion. Concurrently, dislocations shear the γ′ phase, leading to the formation of superlattice intrinsic stacking faults and Kear–Wilsdorf locks, thereby enhancing tensile strength. However, at 950 °C, dislocation motion primarily involves climb, carbides decompose, the γ′ phase softens and enlarges, resulting in a notable decrease in tensile strength. [ABSTRACT FROM AUTHOR]

Nickel-based single crystal superalloys have broad application prospects in the aerospace field. Their excellent physical properties enable the workpiece to serve in complex environments for a long time, and are often used in the most complex stress and the worst working conditions. However, the damage caused by mechanical material removal deteriorates the wafer surface flatness and die strength, while its surface and subsurface formation principle has yet to be revealed. This study aims to analyze the influence of abrasive particles on the load of the workpiece during machining was scrutinized through the lens of stress tensor, yield performance, and third invariant. The results indicate that, a substantial stress load is exerted on the front end of the abrasive grain, leading to the yield deformation of the workpiece. Conversely, the stress load at the bottom of the abrasive grain is comparatively lower, resulting in tensile deformation and the formation of a discernible plastic damage layer. To delve deeper into the workpiece's damage phenomenon, this study conducts a comparative analysis from the standpoints of chips, surface morphology, and subsurface characteristics of DD5. Experimental results indicate that the chips on the contact surface exhibits a relatively smooth texture, while the grinding surface manifests grooves of varying depths. Concurrently, subsurface analysis reveals the presence of slip deformation and elemental flow. This investigation elucidates the intricate interplay between the grinding process and subsurface loading, offering valuable insights to enhance the quality and precision of nickel-based single-crystal superalloy workpiece manufacturing. • The stress load is impacted by the variation in grinding parameters, but the stress value applied by abrasive is slightly affected. • Subsurface deformation is linked to the frequency of serrated chip formation. • Low wheel speed combined with high feed rate and grinding depth causes more noticeable scratches on the workpiece's surface. • Workpiece surface becomes more microhard than the substrate, and the microhardness is increased by about 15 μm. [ABSTRACT FROM AUTHOR]

The current work investigates the metallurgical and corrosion characteristics of the interface between Nickel foam and AA7075 alloy. Nickel foam is conjoined with AA7075 alloy (composite) through a melt-infiltration technique. The composite specimen is characterized for microstructure, microhardness, microhardness, exfoliation corrosion susceptibility, and electrochemical corrosion parameters, including corrosion potential, corrosion current density, and polarization resistance. Also, the influence of T6 heat treatment on the corrosion of the composite specimen is analyzed. The texture, morphology, and composition of the interface and corroded surface are comprehensively analyzed using instrumental analytical techniques such as Scanning Electron Microscopy (SEM), Electron Backscatter Diffraction (EBSD), Energy-Dispersive X-ray Spectroscopy (EDS), and X-ray diffraction. The results indicate that T6 heat treatment increases the corrosion resistance of the composite specimen. [ABSTRACT FROM AUTHOR]

This research investigates the coupling effect of microstructure and temperature on the fatigue performance of an equiaxed Ni-base superalloy, EA, at design-significant temperatures (750–930°C) for different strain amplitudes (Δϵ/2). It is observed that distinguishing damage features (specific to the temperature and Δϵ/2) remarkably affect the extent and distribution of strain localisation, leading to the divergence in associated fatigue behaviour. The strain is uniformly distributed at lower Δϵ/2 for all temperatures. Compared to the 850 and 930°C, the strain localisations at 750°C are more effectively alleviated, accounting for the highest fatigue life. Moreover, this alloy exhibited a bilinear Coffin-Manson (C–M) relationship. It is ascertained that the strain localisation resulting from the dislocation and precipitates (γ′, Cr6C23, and γ-γ′ eutectic) interactions are mainly responsible for the dual-slope C–M behaviour. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to investigate the effect of chemical nickel plating and mechanical alloying on the mechanical and tribological properties of FeS/iron-based self-lubricating materials as well as the wear mechanism of the materials. Design/methodology/approach: Surface modification of FeS powder was carried out by chemical nickel plating method and mechanical alloying of mixed powder by ball milling. The mechanical properties of the material were tested by tribological testing by M-200 ring block type friction and wear tester. Optical microscope was used to observe the surface morphology of the material and the transfer film on the surface of the mate parts, and scanning electron microscope and EDS were used to characterize the wear surface. Findings: Mechanical alloying ball milling was carried out so that the lubricating particles in the matrix are uniformly dispersed; nickel-plated layer enhances the interfacial bonding of FeS and the matrix, and the combination of the two improves the mechanical properties of the material, and at the same time the friction side of the surface of the lubrication of FeS lubricant transfer film formed is denser and more intact, and the friction coefficient of friction side and the wear rate of the material have been greatly reduced. Originality/value: This work aims to improve the mechanical and tribological properties of FeS/iron-based self-lubricating materials and to provide a reference for the preparation of materials with excellent overall properties. [ABSTRACT FROM AUTHOR]

Coherent precipitation, a common strengthening approach, is typically subjected to spatial non-uniformity due to microscopic segregation, leading to multi-scale stress heterogeneity. Such heterogeneity remains poorly characterized because unavailable local strain-free lattice parameters invalidate traditional diffraction-based stress measurement techniques. To overcome these limitations, we demonstrate a submicron-resolved synchrotron X-ray diffraction method to map coherency stress distribution based on the γ/γ′ lattice misfits in Ni-based superalloys. Assisted by finite element analysis, sub-dendritic stresses are deduced from heterogeneous coherency stresses, confirmed by the diffraction experiments. The methodology offers a comprehensive framework to assess stress heterogeneity at multi-scales for all coherent precipitation strengthened alloys. Impact statement This study marks the first successful quantification of stress heterogeneity at multi-scales in alloys strengthened by non-uniform coherent precipitation, even in absence of strain-free lattice constants. [ABSTRACT FROM AUTHOR]

Oxide inclusions in Ni-based superalloys play a crucial role in determining their mechanical properties, oxidation resistance, and corrosion resistance at high temperatures. In this paper, the source and formation mechanism of different types of oxide inclusions in a high-aluminum Ni-based superalloy were systematically studied. An automatic field emission scanning electron microscope equipped with an energy dispersive spectrometer and a self-designed superalloy inclusion analysis standard was utilized to quantitatively reveal the oxide inclusion characteristics of the high-aluminum Ni-based superalloy prepared via vacuum induction melting (VIM) and vacuum induction remelting (VIR) processes. The experimental results indicate that the typical oxide inclusions in the Ni-based superalloy before the VIR process are irregular MgO·Al2O3 inclusions with sizes of less than 2 μm. After the VIR process, the typical oxide inclusions in the Ni-based superalloy are also MgO·Al2O3 inclusions. However, these oxide inclusions can be classified into three categories: (i) endogenous irregular MgO·Al2O3 inclusions, less than 4.3 μm in size, inherited from the master alloy; (ii) several hundred-micron film-like MgO·Al2O3 inclusions generated as interface reaction products between the MgO crucible and melts; and (iii) millimeter-scale MgO·Al2O3 inclusions and several tens of microns of MgO inclusions from the exfoliation of the MgO crucible matrix. [ABSTRACT FROM AUTHOR]

In this study, the dissolution, collision, aggregation, and separation behaviors of nitride inclusions at the melt interface of GH4169 nickel-based superalloy were investigated via thermodynamic calculations combined with in situ observation via high-temperature confocal laser scanning microscope (CLSM). The results showed that the nitride inclusions were able to dissolve completely during the alloy melting process, and boundary layer diffusion was the limiting factor for dissolution. Nitride inclusions from the remelting process were reprecipitated during solidification. As the melt temperature increased, the degree of dissolution of the inclusions increased, and the dissolution rate of the inclusions increased. Second, the results of in situ observation by CLSM showed that nitride inclusions were more likely to aggregate with oxide inclusions, that separation may still occur between nitride inclusions after aggregation. The attraction of nitride–oxide inclusions was greater than that of nitride–nitride inclusions. The ability of the inclusions in the collision zone to aggregate together in contact depends on the interaction forces between the inclusions. The calculation results showed that the cavity bridge force was much greater than the capillary force and van der Waals force, which were the main forces leading to aggregation between the inclusions. Once a stable cavity bridge was formed between the inclusions, the aggregated inclusions no longer separated. In contrast, if cavity bridges formed between inclusions were substable, then fluctuations in the alloy melt would cause the substable structure to rupture, leading to the separation of inclusions. [ABSTRACT FROM AUTHOR]

Dental implants have emerged as an important treatment in modern dentistry for repairing lost teeth, providing patients with enhanced oral function, aesthetics, and overall quality of life. An optimal dental implant minimizes peak stress values at the interface between the implant and the bone while optimizing anchoring strength in the human jawbone under specified standard loads. Implant design controls stress concentration at the bone-implant interface, which influences the biological reaction of the bone. This paper models an optimal thread design to minimize stress distribution surrounding the jawbone. Cylindrical dental implants with micro-threading and square threading improve anchoring and reduce screw loosening, thereby optimizing performance. Biomaterials used in the implant also play a major role. Ni-Ti shape memory alloys (SMAs) have unique characteristics such as biocompatibility, excellent wear and corrosion resistance, and functional features like superelasticity and the shape memory effect, making them suitable for a wide range of biomedical applications. Dental implant design has focused on modifying the shape, size, material, and surface topography to meet market demands. Consequently, the modeling of a dental implant with an improved threading type in the implant body has been accomplished with precise dimensions using SolidWorks 3D CAD software. COMSOL Multiphysics, based on finite element analysis, is then used to analyze the biomechanical properties by importing an STL file from SolidWorks. Several biomechanical factors affect the effectiveness of dental implants, including the nature of loading, the properties of the material used, the shape and geometry of the implants, the quantity and quality of bone around the implants, the surgical technique, and the degree of rapid integration of the implant surface with the jawbone. [ABSTRACT FROM AUTHOR]

CO2 reduction by CH4 (CRM) to produce fuel is of great significance for solar energy storage and eliminating greenhouse gas. Herein, the catalyst of ultrafine Ni nanoparticles supported on CeZrNiO2 solid solution (Ni@CZNO) was synthesized by the sol-gel method. High yield of H2 and CO (58.0 and 69.8 mmol min-1 g-1) and excellent durability (50 h) were achieved by photothermal catalytic CRM merely under focused light irradiation. Structural characterization and DFT calculations reveal that CZNO has rich oxygen vacancies that can adsorb and activate CO2 to produce reactive oxygen species. Oxygen species are transferred to ultrafine Ni nanoparticles through the rich Ni-CZNO interface to accelerate carbon oxidation, thereby maintaining the excellent catalytic stability of the catalyst. Moreover, the experimental results reveal that light irradiation can not only enhance the photothermal catalytic CRM activity through photothermal conversion and molecular activation, but also improve the stability by increasing the concentration of oxygen vacancies and inhibiting CO disproportionation. [ABSTRACT FROM AUTHOR]

Cobalt- and nickel-based superalloys are being extensively used in aerospace, automotive and medical applications due to their specific properties, which include working at high temperatures and stresses, good corrosion and oxidation resistance. This paper incorporates a review on the machinability aspects of nickel- and cobalt-based superalloys in turning operations. The machinability aspects like tool wear and surface integrity are critically reviewed for turning operation. Also, the effect of parameters, such as coating, cooling methods, cutting speeds and feed rate on tool wear, is reviewed critically. The different tool wear mechanisms that occur during machining of these superalloys are studied along with surface integrity, which include surface roughness and microstructures. Lastly, conclusions drawn are based on parameters that need to be improved for sustainable machining of nickel- and cobalt-based superalloys. This review will guide researchers and manufacturers for proper understanding of parameters selection. [ABSTRACT FROM AUTHOR]

This study introduces an advanced computational method aimed at accelerating continuum-scale processes using crystal plasticity approaches to predict mechanical responses in cobalt-based superalloys. The framework integrates two levels, namely, sub-grain and homogenized, at the meso-scale through crystal plasticity finite element (CPFE) platforms. The model is applicable across a temperature range from room temperature up to 900   ° C, accommodating various dislocation mechanisms in the microstructure. The sub-grain level explicitly incorporates precipitates and employs a dislocation density-based constitutive model that is size-dependent. In contrast, the homogenized level utilizes an activation energy-based constitutive model, implicitly representing the γ ′ phase for efficiency in computations. This level considers the effects of composition and morphology on mechanical properties, demonstrating the potential for cobalt-based superalloys to rival nickel-based superalloys. The study aims to investigate the impacts of elements including tungsten, tantalum, titanium, and chromium through the homogenized constitutive model. The model accounts for the locking mechanism to address the cross-slip of screw dislocations at lower temperatures as well as the glide and climb mechanism to simulate diffusions at higher temperatures. The model's validity is established across diverse compositions and morphologies, as well as various temperatures, through comparison with experimental data. This advanced computational framework not only enables accurate predictions of mechanical responses in cobalt-based superalloys across a wide temperature range, but also provides valuable insights into the design and optimization of these materials for high-temperature applications. [ABSTRACT FROM AUTHOR]

In this article, the results of research on a NiTi alloy with a high nickel content (51.7 at.%), produced using the additive technology SLM method and subjected to isothermal ageing after solution annealing, are presented. The study involved the determination of the sequence of phase transformations occurring using differential scanning calorimetry (DSC) and the determination of the temperature range of these transformations. In parallel, the phase composition was determined using the XRD method; the hardness and the Young's modulus were also determined. The analysis of the DSC results obtained indicates the following characteristic features of the NiTi alloy, which change with ageing time: (1) During cooling (from +150 °C to −50 °C), the type of transformation changes from a one-step transformation after solution annealing to a two-step transformation after the ageing process over 1, 20, and 100 h at 500 °C; (2) during heating (from −50 °C to +150 °C) for all the samples, regardless of the ageing time, only a one-step transformation from martensite M(B19′) to austenite A(B2) is observed; (3) the temperature at which the transformation starts increases with the ageing time; (4) the width of the total temperature range of the transformation M(B19′) → A(B2) during heating changes from large (ΔT = 49.7 °C), after solution annealing, to narrow (ΔT = 19.3 °C and ΔT = 17.9 °C after 20 h and 100 h of ageing); and, most importantly, (5) a comparison with the literature data shows that, irrespective of the composition of the NiTi alloy and the manufacturing technology of the alloy samples (regardless of whether this was traditional or additive technology), a sufficiently long ageing process period leads to the occurrence of the martensite → austenite transformation in the same temperature range. [ABSTRACT FROM AUTHOR]

Aero-engines can be exposed to One Engine Inoperative (OEI) conditions during service, and the resulting overheating effect may significantly impact their structural integrity and flight safety. This paper focuses on the influence of overheating on the microstructural evolution and tensile properties of the GH4720Li alloy, a nickel-based polycrystalline superalloy commonly used in turbine disks. Based on the typical OEI operating conditions of a real aero-engine, a series of non-isothermal high-temperature tensile tests involving an OEI stage of 800 °C were conducted. The effects of OEI-induced overheating on the microstructure and tensile properties of the GH4720Li alloy were investigated. The results showed that, after OEI treatment, the primary γ′ phase in this alloy was partially dissolved. The GH4720Li superalloy also exhibited numerous microcracks at the grain boundaries, resulting in complex effects on its tensile properties. The alloy's yield strength and ultimate tensile strength were slightly decreased, whereas its ductility decreased considerably. The OEI-induced embrittlement phenomenon was mainly caused by the non-uniform distribution of the tertiary γ′ phase within grains. The formation of microcracks nucleated at the interfaces between the primary γ′ precipitates and γ matrix phase was another key factor. [ABSTRACT FROM AUTHOR]

A third-generation nickel-based single-crystal superalloy, DD90, was brazed with a Co-based filler alloy under vacuum conditions. The microstructural evolution of the joints brazed with different processing parameters and their effects on the mechanical properties were studied. Many brittle compound phases were formed in the non-isothermal solidification zone, mainly consisting of M3B2 and CrB. With increased bonding temperatures, the isothermal solidification zone increased in thickness and became a continuous region with the filler alloy zone (FAZ). With increasing bonding time, the alloying elements sufficiently diffused into the base metal, and the sizes of the compounds in the joint decreased. In addition, the Re contents of the M3B2 and CrB phases were relatively high compared to those of the γ and γ′ phases, and Re exhibited a special diffusion mechanism and influenced the evolution in the joint microstructures. High-temperature creep rupture tests of the joints were carried out at 980 °C/75 MPa. These joints fractured in the FAZ via typical quasicleavage fracture. The cracks initiated and propagated along the brittle compounds in the FAZ, and finally, the cracks connected with each other, leading to fracture. The numbers, sizes and distribution characteristics of the compounds in the joint had a significant effect on the creep rupture life of the joint. [ABSTRACT FROM AUTHOR]

One impeding factor for faster solidification in typical investment casting processes is the limited heat removal capability. This study compares the classical Bridgman technique and the fluidized carbon bed cooling (FCBC) casting method. In particular, the influence of the thermal design is investigated in terms of microstructural and compositional homogeneity in single-crystalline CMSX-4. These investment casting processes mainly differ in the baffle type used to insulate the hot and cold zones inside of the casting vessel. While the Bridgman process is based on radiation cooling, the FCBC casting process relies on a dynamic baffle made of expanded graphite that is buoyant on fluidized bed of glassy carbon beads. Such a dynamic insulation layer can adapt to the crosssectional variation of ceramic shell molds and provide a better thermal insulation, which results in more uniform solidification conditions. This enables a reduction in the primary dendrite arm spacing by up to 26%, an increase in the homogeneity of the microstructure and composition, as well as a reduction in overall porosity and mean pore size of 41%. [ABSTRACT FROM AUTHOR]

The synergistic effects of boron (B) and rare earth (RE) elements on the microstructure and stress rupture properties were investigated in a Ni-based superalloy. The stress rupture lifetime at 650 °C/873 MPa significantly increased with the addition of B as a single element. Furthermore, the stress rupture lifetime reached its peak (303 h), with a certain amount of B and RE added together in test alloys. Although the grain size and morphology of the γ′ phase varied a little with the change in B and RE addition, they were not considered to be the main reasons for stress rupture performance. The enhancement in stress rupture lifetime was mostly attributed to the segregation of the B and RE elements, which increased the binding force of the grain boundary and improved its strength and plasticity. In addition, the enrichment of B and RE inhabited the precipitation of carbides along grain boundaries. Furthermore, nano-scale RE precipitates containing sulfur (S) and phosphorus (P) were observed to be distributed along the grain boundaries. The purification of grain boundaries by B and RE elements was favorable to further improve the stress rupture properties. [ABSTRACT FROM AUTHOR]

In the study, four novel Ni-based superalloys were produced and radiation shielding efficiencies of the alloys were investigated. Ni, Fe, Mo, Cr, Ta and W were selected for developing NiyTaxW7Cr7Fe7Mo7B7 (x = 0–20; y = 65–45%) alloys based on Ni. Phy-X/PSD code was used to calculate the attenuation parameters. Results were compared by XCom and some reported values in the literature for a meaningful evaluation. In addition, experimental results were provided based on x-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy and electron paramagnetic resonance spectroscopic techniques. It is obtained that the crystallite sizes of the alloys calculated based on the Debye Scherrer equation vary between 44.13 and 68.33 nm. The mapping images and EDS analysis indicate that the Ni3 alloy has the most homogeneous structure. There is a direct relation between the amount of Ta and the radiation protection capability of the alloys. Newly fabricated Ni-based superalloys have good shielding properties and the usability of the alloys can be recommended as effective shielding materials in radiation-related applications. [ABSTRACT FROM AUTHOR]

The effect of oxide scale and microstructural changes during 10, 20, and 40 hot corrosion cycles on the high-temperature tensile properties of Rene-80 superalloy at 950 °C was investigated. Due to the formation of micro-cracks and micro-voids, compressive stresses produced from Cr2O3 and NiO growth, and tensile stresses stemming from NiMoO4 transformation and Al internal oxidation, the oxide scale spalled. By increasing the hot corrosion cycles, UTS (Ultimate Tensile Strength) and El.% (Elongation) first decreased and then increased due to the propagation of intergranular vertical cracks from the oxide scale to the Rene-80 after 20 cycles. During hot corrosion cycles, YS increased due to a rise in the density of near-surface intergranular cracks close to the Rene-80/oxide scale interface resulting from micro-void linkage and γ′-depleted zone. Due to the high area fraction and the small average size of secondary γ′, UTS and YS were the highest and lowest after ten cycles, respectively. [ABSTRACT FROM AUTHOR]

One of the main problems of superhydrophobic coatings is the low mechanical and chemical stability, which limits the industrial applications of these coatings. The purpose of this research is to create Ni-PTFE composite coatings with hierarchical morphology by electrodeposition method, in order to increase the corrosion resistance, and to improve the mechanical and chemical stability. Ni-PTFE Composite coatings were fabricated by adding different concentrations of PTFE particles (5, 10, 15, 20, 30, and 40 g/L) into the Ni electrodeposition bath. The effect of PTFE concentration on morphology, wettability, and corrosion resistance of the coatings was investigated. The results showed that when an optimum concentration of PTFE (15 g/L) is introduced in the electrodeposition bath, not only the hierarchical morphology of the Ni coating is preserved; but also the maximum contact angle of 158° and the minimum corrosion current density of 0.03 µA/cm² was achieved. The long-term chemical and mechanical stability tests showed that by embedding of PTFE particles with hydrophobic nature, into the hierarcically structured superhydrophobic nickel coatings, higher mechanical and chemical stability is obtaind. [ABSTRACT FROM AUTHOR]

Carbon nanofibers (CNFs) and graphene nanosheets (GNs) are introduced to obtain nano-sized TiC particles in a novel additive manufactured Ni-Co-based superalloy. The double strengthening effects of reaction-induced TiC and remaining CNFs/GNs are conceptualized in the present paper. The CNFs and GNs act as heterogeneous nucleation sites for the formation of uniformly distributed TiC nanoparticles, which inhibits the crack and homogenize the microstructure. Interestingly, the existence of remaining GNs/CNFs is revealed via 3D atom-by-atom tomographic reconstruction technology for the first time. This unique combination of nanoparticles and residual CNFs/GNs nanofillers has great potential to develop superalloys with excellent properties. The formation of nano-sized dispersion TiC particles is induced by the introduction of carbon nanofibers and graphene nanosheets in additive manufactured superalloy, which inhibits the crack and homogenizes the microstructure. [ABSTRACT FROM AUTHOR]

Nanocrystalline alloys are noteworthy for their high strength, and nanocrystalline Ni is being investigated for high-temperature applications. However, nanocrystalline alloys are unstable against coarsening, thereby prone to degradation of strength. In this work, two nanocrystalline alloys, Ni–(0, 11 at pct W)–3 at pct Ta–2 at pct Y, were designed to exhibit microstructural stability and high strength by forming nanoscale precipitates, maintaining stable nanoscale grains to exploit Hall–Petch hardening, and decreasing the stacking fault energy of the Ni-based matrix. Produced via high-energy cryogenic mechanical alloying, both alloys exhibited thermal stability and enhanced mechanical properties due to beneficial impurity yttrium oxide/nitride particles and argon bubbles that pin grain boundaries. Hardness testing and advanced characterization techniques, namely scanning transmission electron microscopy, were used to elucidate microstructure–property relationships. The difference in impurity ceramic phase affected the alloys' relative stability and hardness. The Ni–11W–3Ta–2Y alloy with Y2O3 nanoparticles was even more stable and harder than the Ni–3Ta–2Y alloy with YN particles, maintaining nanoscale grains after annealing at 70 pct homologous temperature for 100 hours and demonstrating hardness enhanced by over 2 GPa above the Hall–Petch contribution. The yttrium oxide/nitride particles, Ni5Y intermetallic phase, and pure artifact W/Ta grains remaining from milling, play a role in the enhanced hardening. [ABSTRACT FROM AUTHOR]

Novel compositionally complex CoNiCr-based superalloys with excellent mechanical properties have been developed, which combine the multiprincipal element nature of high-entropy alloys with the precipitation strengthening in superalloys. A series of advanced polycrystalline γ′-strengthened CoNiCr-based superalloys, called CoWAlloys, with varying contents of Al, W, Ti, Ta, Mo, and Nb are investigated in terms of microstructure, thermophysical properties, yield, and creep strength. The microstructure of all CoWAlloys consists of an fcc solid solution matrix phase (approximate γ composition in at. pct: 50Co–20Ni–20Cr–10X (X = other alloying elements)), which is strengthened by a multicomponent γ′ (Ni,Co)3(Al,Ti,Ta,W,Nb)-based precipitate phase with a very high-volume fraction of around 60 vol pct (approximate γ′ composition in at. pct: 45Ni–30Co–25X). These alloys have high solidus temperatures above 1300 °C and moderate γ′ solvus temperature between 985 °C and 1080 °C leading to a large processing window. The increasing content of γ′-forming elements Ti, Ta, W, and Nb decreases this window, but increases the γ/γ′ lattice misfit and the anti-phase boundary energy, which contribute to a significantly higher yield and creep strength. Their properties are discussed in comparison with conventional polycrystalline Ni-base superalloys and so-called L12-strengthened high-entropy alloys, revealing that the creep strengths of the CoWAlloys are significantly higher. This is due to the reduced strain rate sensitivity of the CoWAlloys due to different underlying deformation mechanisms: By increasing the anti-phase boundary energy, a transition to stacking fault shearing and microtwinning occurs, which leads to the enhanced creep strength. Based on these results, guidelines and strategies for the design of next-generation advanced high-temperature polycrystalline superalloys are proposed. [ABSTRACT FROM AUTHOR]