Search

In this work, a comparative study of the tribological performance of two hard coatings, CrN/TiBN, was conducted for research purposes and industrial applications in food products, particularly for food packaging into cans using the double hermetic sealing process. CrN and TiBN coatings were successfully deposited on a base-cobalt metal substrate of a CoCrW commercial alloy using physical vapor deposition by arc evaporation (AEPVD) technology to improve the tribological properties of the commercial alloy, including wear and corrosion resistance, lower coefficient of friction, and overall durability. This research focuses on conducting scratch and abrasion wear resistance tests in dry conditions; specifically, it pursues to evaluate the wear corrosion properties, known as tribocorrosion performance, on CrN/TiBN hard coatings. The experimental results show that the CrN coating (2.9 μm) is slightly thicker than the TiBN coating (2.7 μm), with a 47 N critical load. It also shows a lower coefficient of friction (CoF) in a dry environment, while the TiBN coating showed total detachment and a high coefficient of friction in a dry environment condition. Tribocorrosion testing in brine aqueous solution indicated that CrN coating shows a high friction coefficient with a higher open circuit potential value (Ecorr), and TiBN shows the lowest corrosion potential (Ecorr) and the lowest friction coefficient. This suggests that CrN could provide better corrosion protection for commercial cobalt alloys and improve tool performance during the food canning process in brine environments. [ABSTRACT FROM AUTHOR]

The present research aims to improve the surface quality of laser powder bed fusion (LPBF) built cobalt chrome alloy (CoCr) by pulse laser remelting. The laser power, overlap percentage, and spot diameter are varied to determine the best parameters for laser polishing. The microhardness and microstructural changes associated with pulse laser remelting are described. Surface morphology and surface roughness parameters are reported for various laser remelting parameters. Among the three different spot diameters, 1, 2, and 3 mm, the maximum (> 50%) reduction in surface roughness was obtained for 2 mm with 1J laser energy and 50% X and 20% Y as well as 20% X and 50% Y overlaps. A DoE- and RSM-based approach has been utilized for parametric optimization of the surface roughness. The squared laser power is identified as a critical parameter by ANOVA. A Pareto chart confirms the significance of squared laser power across spot diameters. Optimization suggests that a 2-mm spot diameter works best with specific parameters to produce a better surface finish. However, the nanosecond order laser pulses have a limitation on the depth of surface modification without severe ablation and thereby on the reduction in the surface roughness. [ABSTRACT FROM AUTHOR]

A high-temperature synthetic approach is used to prepare a series of pseudo-binary phases- Co2-xNixZn11. In the structures of Co2-xNixZn11, the statistical distribution between Co and Ni that is suggested by compositional analysis is confirmed by combined refinements of X-ray and neutron powder diffraction (NPD) experimental data. The aforementioned phases adopt a body-centered cubic lattice with a noncentrosymmetric space group I43m (217). Their crystal structures comprise two 26-atom γ-brass clusters. Each γ-cluster is made of four sequential polyhedral shells: inner tetrahedron (IT), outer tetrahedron (OT), octahedron (OH), and distorted cuboctahedron (CO). Diffraction experiments and the computations endorse that the OT site is statistically distributed by Co and Ni atoms, while the other three sites (IT, OH, and CO) are occupied by Zn atoms. The density of states (DOS) curve for Co1.5Ni0.5Zn11 displays a similar feature as binary Co2Zn11, whereas the wide pseudo-gap is formed near EF as Ni-concentration increases in Co2-xNixZn11. Bonding analysis shows that this specific atomic distribution nearly optimizes heteroatomic Co/Ni--Zn contacts in the Co1.0Ni1.0Zn11 and Co0.5Ni1.5Zn11. The Co1.7Ni0.3Zn11 exhibit paramagnetic behavior, whereas Co0.5Ni1.5Zn11 shows distinct diamagnetic behavior. With the increase in Ni concentration in the structure of Co2-xNixZn11, Ni atoms gradually substitute the Co atoms at OT sites; hence, magnetic characteristics change from para- to diamagnetism. [ABSTRACT FROM AUTHOR]

This study was intended to investigate the mechanical property at high temperature and cutting performance of cemented carbide for machining of exotic materials, such as nickel alloys, cobalt alloys, and titanium alloys. Exotic materials are widely used for equipment and parts in the aerospace and automotive industries due to their superior heat and corrosion resistance. When machining exotic materials, its low thermal conductivity causes the cutting edge temperature to be higher than when cutting steel, and the hardness of the tool material decreases, resulting in extremely low tool life. However, because cemented carbide in particular contains metals in its composition, plastic deformation of the cemented carbide cannot be prevented even when the coating has sufficient heat resistance. The WC-Co-NiCr alloy, in which NiCr partially replaces Co as the binder phase of cemented carbide, has improved high-temperature properties while maintaining room temperature properties compared with conventional WC-Co alloys, and tool life has been improved in machining exotic alloys. [ABSTRACT FROM AUTHOR]

[Display omitted] • Surface partially oxidized Re 3 Co 2 @NCF was synthesized via a hydrothermal followed by pyrolysis strategy. • The Re 3 Co 2 @NCF electrocatalyst exhibited outstanding HER performance and stability in alkaline condition. • The partially oxidized surfaces resulting from the electronic interaction between Re and Co led to the enhanced HER activity. Although the theoretical electrocatalytic activity of rhenium (Re) for the hydrogen evolution reaction is comparable to that of platinum, the experimental performance of reported rhenium-based electrocatalysts remains unsatisfactory. Herein, we report a highly efficient and stable electrocatalyst composed of rhenium and cobalt (Co) nanoalloy embedded in nitrogen-doped carbon film (Re 3 Co 2 @NCF). The Re 3 Co 2 @NCF electrocatalyst exhibited remarkable hydrogen evolution performance, with an overpotential as low as 30 ± 3 mV to reach a current density of 10 mA cm−2. In addition, the Re 3 Co 2 @NCF demonstrated exceptional stability over several days at a current density of 150 mA cm−2. Theoretical calculations revealed that alloying cobalt with rhenium altered the electronic structure of the metals, causing partial oxidation of the superficial metal atoms. This modification provided a balance for various intermediates' adsorption and desorption, thereby boosting the intrinsic activity of rhenium for hydrogen evolution reaction. This work improves the electrocatalytic performance of rhenium to its theoretical activity, suggesting a promising future for rhenium-based electrocatalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] The optimization of the adsorption of oxygen-containing intermediates on platinum (Pt) sites of Pt-based electrocatalysts is crucial for the oxygen reduction reaction process. Currently, a large amount of researches mainly focus on modifying the bulk structure of the electrocatalysts, however, the vital role of solvent effect on the phase interfaces is often overlooked. Here, we successfully developed an electrocatalyst in which the ordered PtCo alloy anchors on the cobalt (Co) single-atoms/clusters decorated support (Co 1,n N C) and its surface is further optimized using hydrophobic ionic liquid (IL). Experimental studies and theoretical calculations indicate that compressive stress on Pt lattice contributed by intrinsic structure and the local hydrophobicity caused by IL on the surface can suppress the stabilization of *OH on Pt. This synergistic effect affords outstanding catalytic performance, exhibiting a half-wave potential (E 1/2) of 0.916 V vs. RHE and a mass activity (MA) of 1350.3 mA mg Pt −1 in 0.1 mol/L perchloric acid (0.1 M HClO 4) electrolyte, much better than the commercial Pt/C (0.849 V vs. RHE and 145.5 mA mg Pt −1 for E 1/2 and MA, respectively). Moreover, the E 1/2 of IL-PtCo/Co 1,n N C only lost 5 mV after 10,000 cyclic voltammetry (CV) cycles due to a strong and synergistic contact of the intermetallic PtCo alloy with the Co 1,n N C support and IL. This research provides an effective method for designing efficient electrocatalysts by combining intrinsic structure and surface modification. [ABSTRACT FROM AUTHOR]

Introduction: As an economical and fast process method for surface modification of materials, overlay welding is increasingly widely used in the manufacturing and repair of parts in various industrial sectors. Methods: This study combines grating projection measurement to design an economical mold arc additive process, and introduces point cloud simplification algorithm for wear and repair design of the mold structure. Then, a new method for manufacturing low-cost, long-life, and economical hot stamping die inserts is designed, using low-cost forged steel and cast steel as substrates and surface welding of high-temperature alloy wear-resistant layers. Results and Discussion: The experiment shows that the proposed algorithm for simplifying scattered molds has a good evaluation effect, without any gaps, and has a good retention effect on point clouds. The maximum and minimum distances are 0.45mm and 0.025 mm, respectively. The friction coefficient of cobalt based alloys at 300°C is lower than that at 200°C, and the fluctuation period at 200°C is significantly longer than that at 300°C. HSTS steel has the highest wear resistance, and the performance of cobalt-based alloys is significantly better than that of other alloys. The compressive yield strength of iron-based alloys is the highest, and the hardness of iron-based alloys is the highest, at 53.2 HRC. Therefore, iron-based alloys were selected as a surface wear-resistant layer welding material for economical molds with cooling channels, and cobalt-based alloys were also selected as a surface wearresistant layer welding material for variable strength economical molds. The research results provide a reference for economic mold manufacturing and repair. [ABSTRACT FROM AUTHOR]

This article focuses on the compressive yield strength testing of powder metallurgy (PM) copper steels. It highlights the lack of data on compressive yield strength in the standard for PM structural parts and discusses previous testing on PM nickel steel. Concerns about conservative values and a recent testing program that led to the approval of higher values for PM copper steels are also mentioned. The document presents microindentation hardness measurements and microstructures of specific specimens, summarizes the compressive yield strength values, and provides new "typical" values for FC-0205HT and FC-0208HT materials. These values aim to offer design engineers more realistic properties for specifying PM materials. [Extracted from the article]

To extend the service life of 316L stainless steel components in harsh environments, this study utilized laser cladding technology to enhance the hardness, wear resistance, and corrosion resistance of the 316L stainless steel surface. Nickel-based and cobalt-based cladding layers were prepared on the surface of the 316L stainless steel, and the microstructure and phases of the layers were analyzed using scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. In addition, the hardness of the substrate and the cladding layers was tested with a microhardness tester, the frictional wear performance was tested with a pin on disc wear tester, and the corrosion resistance was tested with an electrochemical workstation. The experimental results indicate that the nickel-based cladding layer primarily comprises the γ-(Fe, Ni), Cr7C3, and Ni3Si phases, with equiaxed and dendritic grains being the predominant morphologies. By contrast, the cobalt-based cladding layer mainly comprises the γ-Co, Cr7C3, and Co7W6 phases, with columnar and dendritic grains being the predominant morphologies. Both cladding layers displayed a significantly better microhardness, wear resistance, and corrosion resistance than the substrate. Between the two cladding layers, the nickel-based cladding layer demonstrated a superior microhardness, whereas the cobalt-based cladding layer slightly outperformed in wear resistance and corrosion resistance. The findings from our results are important for understanding the performance of laser-cladding layers and laying a scientific basis for the promotion and optimization of laser cladding technology in industrial applications. Moreover, our results showed that laser cladding technology is increasingly important in extending the service life of components and improving the material performance. [ABSTRACT FROM AUTHOR]

Transforming current complementary metal–oxide–semiconductor (CMOS) technology to fabricate memory chips and microprocessors into environmentally friendlier electronics requires the development of new approaches to resource- and energy-efficient electron transport and switching materials. Metal and multi-metal oxide layers play a key role in high-end technical applications. However, these layers are commonly produced through high-energy and high-temperature procedures. Herein, we demonstrate our first attempts to obtain stimuli-responsive mixed-metal oxide thin films from solution-processed molecular precursors under milder conditions. The molecular compounds of interest were prepared by one-pot reactions of a CoII carboxylate complex, triethylamine (Et3N), N-butyldiethanolamine (H2bda), and a hexanuclear complex [Ce6O4(OH)4(piv)12] (Hpiv = pivalic acid) or [Zr6O4(OH)4(ib)12(H2O)]·3Hib (Hib = isobutyric acid) in acetonitrile solution. The resulting charge-neutral, heterometallic coordination compounds display a ligand-supported pentanuclear {Ce IV3 Co III2 } core (in 1) and a dodecanuclear {Zr IV6 Co II6 } core (in 2), exhibiting thermal stability up to ca. 100 °C in air. Compound 2 was deposited and analyzed on Au(111) and SiO2/Si(100) surfaces to explore its potential as a single-molecule precursor for the preparation of atomically precise, complex mixed-metal oxide thin films. The adsorption characteristics of it demonstrate the ability to form stable agglomerates on the investigated surfaces. [ABSTRACT FROM AUTHOR]

Aim: (1) The aim of this study was to evaluate the effect of a ceramic bonder at the metal ceramic interface in sintered and casted cobalt-chromium (Co-Cr) alloy. (2) To compare the shear bond strength between the different manufacturing techniques: Casting and direct metal laser sintering (DMLS). Setting and Design: In vitro comparative study Materials and Methods: For the casting group, 40 clear acrylic patterns with dimensions of 20 mm × 10 mm × 2.5 mm were designed in a software and casted with Co-Cr alloy. For DMLS samples, a standard tessellation language file with the abovementioned dimensions was created through a software to fabricate 40 samples. All the samples were equally distributed into the following four groups: • Group A - Casted samples with the application of Cerambond (n = 20) • Group B - Casted samples without application of Cerambond (n = 20) • Group C - DMLS samples with application of Cerambond (n = 20) • Group D - DMLS without application of Cerambond (n = 20). Ceramic buildup was done on all 80 samples, followed by firing up to a temperature of 920°C in a ceramic furnace. SBS was evaluated using a universal testing machine and failure modes were examined under the electron microscope. Statistical Analysis Used: ANOVA test and Tukey's honestly significance difference post hoc test for multiple comparisons. Results: One-way analysis of variance test revealed that the shear load and bond strength values of all four groups were statistically different with P < 0.001. Post hoc Tukey's test showed statistically significant difference among the four groups. The mean shear strength of Group C was significantly greater when compared to other groups, respectively. Conclusions: Within the limitations of this study, the application of Cerambond to both casted and sintered samples showed significantly increased SBS values and it was also observed that sintered samples had higher strength than casted samples. Altogether, the results indicate that the use of Cerambond increased the shear strength between cobalt Cr alloy and ceramics, thereby prolonging the longevity of the restorations. [ABSTRACT FROM AUTHOR]

Conversion of air and water into valuable chemicals of ammonia (NH3) by plasma activation and electrochemical reduction is a promising approach to achieve zero carbon‐emission synthesis of NH3. However, designing highly efficient electrochemical catalysts is one of the key challenges in accomplishing this strategy. Herein, a self‐supported cobalt–tungsten alloy supported on cobalt foam (CoW/CF) is developed via a simple and efficient method at room temperature. Surprisingly, the catalyst exhibits ultra‐high NH3 partial current density (1559 mA cm−2), superior NH3 yield rate (164.3 mg h−1 cm−2), and high Faradaic efficiency (98.1%) under the condition of 0.2 M nitrate/nitrite, outperforming most of the reported values of electrosynthesis of NH3 to the knowledge. The introduction of W makes the Co atom surface electron deficient, which can enhance the adsorption of NOx− and mitigate the excessive bonding of hydroxyl radicals (OH*) generated during nitrite (NO2*) hydrogenation, thereby reducing the energy barrier of the potential‐determining step. More interestingly, a scale‐up reaction system is established, achieving an NH3 yield rate of 4.771 g h−1 and successfully converting the NH3 in solution into solid NH4Cl. The aforementioned progress significantly enhances the facilitation of NH3 electrosynthesis industrialization. [ABSTRACT FROM AUTHOR]

Temperature-dependent magnetization of core-shell and alloy nanoparticles of cobalt (Co)/nickel (Ni) is investigated within the context of the classical spin Hamiltonian and Monte Carlo simulations. The results of our study indicate that the average temperature-dependent magnetization and magnetic-ordering temperature have a significant influence from variations in the core-shell ratio and chemical order in core-shell nanoparticles. Also, the alloy fraction of Co(Ni) strongly influences the magnetic ordering temperature of the nanoparticles. It is noticed that in alloy nanoparticles, the rise of the magnetic ordering temperature with the increase in Co proportion is linear. However, the same is not true for core-shell nanoparticles where the magnetic-ordering temperature deviates from the straight line fit of alloy T c . It is ascertained that core-shell Co@Ni and Ni@Co nanoparticles sustain higher temperatures in their ferromagnetic state. In the ferrimagnetic nanoparticles, there is a reduction in the saturation magnetization and a display of compensation behavior. [ABSTRACT FROM AUTHOR]

Cobalt alloys have numerous applications, especially as critical components in orthopedic biomedical implants. However, recent investigations have revealed potential hazards associated with the release of nanoparticles from cobalt-based implants during implantation. This can lead to their accumulation and migration within the body, resulting in adverse reactions such as organ toxicity. Despite being a primary interface for cobalt nanoparticle (CoNP) exposure, skeletal muscle lacks comprehensive long-term impact studies. This study evaluated whether selenium nanoparticles (SeNPs) could mitigate CoNP toxicity in muscle cells and zebrafish models. CoNPs dose-dependently reduced C2C12 viability while elevating reactive oxygen species (ROS) and apoptosis. However, low-dose SeNPs attenuated these adverse effects. CoNPs downregulated myogenic genes and α-smooth muscle actin (α-SMA) expression in C2C12 cells; this effect was attenuated by SeNP cotreatment. Zebrafish studies confirmed CoNP toxicity, as it decreased locomotor performance while inducing muscle injury, ROS generation, malformations, and mortality. However, SeNPs alleviated these detrimental effects. Overall, SeNPs mitigated CoNP-mediated cytotoxicity in muscle cells and tissue through antioxidative and antiapoptotic mechanisms. This suggests that SeNP-coated implants could be developed to eliminate cobalt nanoparticle toxicity and enhance the safety of metallic implants. [ABSTRACT FROM AUTHOR]

The influence of texture on strength was investigated by altering the amount of cobalt in Ni-Co alloys. The purpose of incorporating Co was to reduce the stacking fault energy (SFE) of the alloy. A decrease in the SFE reduces the ease of cross-slip and enhances planar slip, leading to changes in texture during cold working. Three Ni-Co alloys (33, 50, and 60 wt pctCo) were wire drawn at room temperature in a specially designed setup to wire diameters of 500, 200, and 100 μm, corresponding to a drawing strain of 2.67, 4.05, and 5.88. EBSD analysis revealed a refinement in grain size with drawing strain as well as a transition from elongated to equiaxed grains in Ni-50 and Ni-60 Co alloys. Line profile analysis and bulk texture analysis showed that increasing drawing strain leads to a higher defect density, an increased <100> fiber fraction and a decreased <111> fiber fraction, with the trends increasing with an increase in Co content. Tensile tests on the drawn wires show that Ni-60 Co alloy has higher strength with superior ductility for all wire diameters. The HP coefficients for the annealed conditions, calculated by annealing Ni-Co wires of 100 μm diameter, was found to be independent of SFE. The HP coefficients in drawn conditions were found to be higher than in the annealed conditions. The activation volume measured from the multiple stress relaxations in the drawn wires ranged from 20 to 5.5 b3, suggesting that dislocation interactions remained the underlying operating deformation mechanism. [ABSTRACT FROM AUTHOR]

In this work, electrochemical deposition techniques (galvanostatic and potentiostatic) were used to obtain coatings of a new composite polymer, 3-methylpyrrole—sodium dodecyl sulfate/poly 2-methythiophene (P3MPY-SDS/P2MT), on cobalt-based alloy samples for anti-corrosion safety. The use of sodium dodecyl sulfate as a dopant ion in electrosynthesis can have a relevant effect on the anticorrosive property of the composite polymer layer by blocking the entry of corrosive ions. The cobalt alloy specimen had an important impact on the electrochemical performance of the composite coating and this together with the presence of the polymeric layer was achieved by simultaneously constitution of a complex oxides film and polymeric layers. The polymeric coatings were analyzed using scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, and cyclic voltammetry (CV) methods. The corrosion protection of the P3MPY-SDS/P2MT-covered cobalt-based alloy was explored using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization procedures in a 1 M HCl solution. The corrosion speed of the P3MPY-SDS/P2MT-covered cobalt-based alloy was observed to be ~10 times less than an uncovered specimen, and the effectiveness of the composite layers of this coating is greater than 91%. This superior efficaciousness was obtained by the electropolymerization of P3MPY-SDS/P2MT at current densities of 1 mA/cm2 and 0.5 mA/cm2, applied potentials of 0.9 V and 1.0 V, and a molar ratio of 5:1. Corrosion test results indicate that the P3MPY-SDS/P2MT coatings provide a good result: protection against the corrosion of a cobalt-based alloy in aggressive solutions. [ABSTRACT FROM AUTHOR]

The CoCrFeNi high entropy alloy (HEA) with face-centered cubic (FCC) crystal structure exhibits excellent ductility values even at cryogenic temperatures. However, since this HEA is relatively weak in strength, it may not meet the requirements of industrial applications in terms of strength-ductility trade-off. Therefore, the systematic addition of yttrium (Y) into CoCrFeNi HEA was investigated in the present study to increase the strength by solid solution and second phase strengthening. The HEAs were produced by vacuum arc melting, suction casting, and subsequent homogenization at 1150 °C for 24 h. The structural development of the HEAs was investigated by using the X-ray diffraction (XRD) technique which revealed the formation of a solid solution phase and CaCu5-type hexagonal structure (HS) second phase. The corresponding microstructure of the HEAs was examined under a scanning electron microscope (SEM) revealing the transformation of the microstructure from elongated grains to nearly equiaxed grains with the increase of Y content from 2 at. % to 4 at. %. The mechanical properties of the HEAs were investigated by using hardness and compression tests. The results exhibited a dramatic increase in the hardness from 143 (±2) HV to 335 (±7) HV and in the yield strength from 130 MPa to 1025 MPa with 4 at. % Y addition. Our study has revealed that the addition of rare earth Y element results in further development in the strength of the CoCrFeNi for potential engineering applications. [ABSTRACT FROM AUTHOR]

In this study, the failure analysis of the second row-nozzles of one of the gas turbine units was investigated. The vanes alloy was FSX-414 cobalt base alloy. The visual evaluations indicated that the leading-edge region of about 8 vanes was completely damaged, and needed to be replaced. The microstructural evaluation was studied by optical microscopy (OM) and scanning electron microscopy (SEM). The results showed that the primary carbides such as M3C2 and M7C3 were dissolved and the secondary carbides with M23C6 composition were formed continuously and coarsely on the grain boundaries. Also, the crack networks were created in the grain boundaries which were propagated throughout the sample thickness. The X-ray diffraction (XRD) and energy disperse spectroscopy (EDS) analyses indicated that hot oxidation and sulfidation have occurred on the leading-edge surface. It seems that the increasing temperature due to the asymmetry of the combustion line had caused such damage. [ABSTRACT FROM AUTHOR]

Hot deformation of sintered cobalt during hot compression testing was investigated in the temperature range of 700–1000 °C and at strain rates ranging from 0.0005 to 0.1 s−1. Cobalt underwent considerable dynamic recrystallization (DRX) during hot deformation, with stress-strain flow curves exhibiting one or several peaks followed by significant flow softening and leading to a steady-state stress. Constitutive equations were used to derive the flow stress behaviour. A physically based model to describe the strain rate as a function of stress was suggested for temperatures ranging between 775 and 1000 °C. In this case, a creep exponent (n) of 5 indicated that the deformation mechanism was controlled by the glide and climb of dislocations. The activation energy coinciding with the one for self-diffusion of ferromagnetic cubic cobalt implied a diffusion-controlled mechanism and the presence of face-centered cubic (FCC) cobalt during deformation. Interestingly, the results at 700 °C could not be perfectly fitted to this model and exhibited a higher resistance to deformation. This revealed that the glide and climb deformation mode was close to the transition where glide mode was dominant, and thus mostly glide occurred at 700 °C, especially for the largest strain rates.

Purpose: To compare the precision of adaptation of cobalt-chromium (Co-Cr) three-unit fixed dental prostheses (FDPs) fabricated using different techniques. Materials and Methods: A master model was prepared to receive a three-unit FDP. This model was duplicated 60 times from a silicone mold. The dies (N = 60) were scanned and divided into three groups (n = 20 each) to receive the FDPs made of pre-sintered Co-Cr (CS), laser-sintered Co-Cr (LS), or cast Co-Cr (Gi). Frameworks were layered with ceramic, and each framework was seated on its specific model. The replica technique was used to measure the marginal and internal discrepancies in the mesiodistal and buccolingual planes. Prepared silicone samples were examined with scanning electron microscopy. Obtained data were analyzed using Levene test, t test, and analysis of variance (α = .05). Results: When overall mean discrepancy values were compared, in mesiodistal planes, LS showed better adaptation than Gi (P = .025). Similar adaptation was found for CS and Gi, and for CS and LS (P = .169 and P = 1.000, respectively). In buccolingual planes, the difference in fit was not significant among the three tested groups (P > .05). In a pairwise comparison between materials, a net increase in values between points 1 and 5 was noted (P = .57). Difference in discrepancy values within points was significant. This was confirmed at abutment level on some measurement points. Within each material, at abutment level, differences were significant at several measurement locations in both the mesiodistal and buccolingual planes. Conclusion: Within the limitations of this study, three-unit Co-Cr FDPs showed similar marginal and internal discrepancy values. Presintered and laser-sintered Co-Cr alloys can be considered for three-unit FDP fabrication. [ABSTRACT FROM AUTHOR]

Materials with high magnetoelectric coupling are attractive for use in engineered multiferroic heterostructures with applications such as ultra-low power magnetic sensors, parametric inductors, and non-volatile random-access memory devices. Iron--cobalt alloys exhibit both high magnetostriction and high saturation magnetization that are required for achieving significantly higher magnetoelectric coupling. We report on sputter-deposited (Fe0.5Co0.5)1-xHfx (x =0 - 0.14) alloy thin films and the beneficial influence of Hafnium alloying on the magnetic and magnetostrictive properties. We found that co-sputtering Hf results in the realization of the peening mechanism that drives film stress from highly tensile to slightly compressive. Scanning electron microscopy and x-ray diffraction along with vibrating sample magnetometry show reduction in coercivity with Hf alloying that is correlated with reduced grain size and low film stress. We demonstrate a crossover from tensile to compressive stress at x ~0.09 while maintaining a high magnetostriction of 50 ppm and a low coercive field of 1.1 Oe. These characteristics appear to be related to the amorphous nature of the film at higher Hf alloying. [ABSTRACT FROM AUTHOR]

This paper aims to reduce power loss in electrical steel by improving its surface resistivity. The proposed approach involves introducing additional alloying elements through diffusion once the steel sheet reaches the desired thickness. Various effective techniques have been suggested and tested to enhance the resistivity of the strip. The method entails creating a paste by combining powdered diffusing elements with specific solutions, which are then applied to the steel's surface. After firing the sample, a successful transfer of certain elements to the steel surface is achieved. The amount and distribution of these elements can be controlled by adjusting the paste composition, modifying the firing parameters, and employing subsequent annealing procedures. This study specifically investigates the effectiveness of incorporating cobalt oxide (II, III) into non-oriented silicon iron to mitigate power loss. The experimental samples consist of non-oriented electrical steels with a composition of 2.4 wt% Si-Fe and dimensions of 0.305 mm × 300 mm × 30 mm. Power loss and permeability measurements are conducted using a single strip tester (SST) within a magnetic field range of 0.5 T to 1.7 T. These measurements are performed using an AC magnetic properties measurement system under controlled sinusoidal conditions at various frequencies. The research explores the impact of cobalt oxide (II, III) addition, observing successful diffusion into the steel through the utilization of a paste based on sodium silicate solution. This treatment results in a significant reduction in power loss in the non-oriented material, with power loss reductions of 14% at 400 Hz and 23% at 1 kHz attributed to the elimination of a porous layer containing a high concentration of the diffusing element. The formation of porosity in the cobalt addition was found to be particularly sensitive to firing temperature near the melting point. The diffusion process was examined through scanning electron microscopy (SEM) in combination with energy-dispersive X-ray spectroscopy (EDS). The results demonstrate improved power losses in the coated samples compared with the uncoated ones. In conclusion, this study establishes that the properties of non-oriented electrical steels can be enhanced through a safer process compared with the methods employed by previous researchers. [ABSTRACT FROM AUTHOR]

Six {Ni,Co}-based alloys containing 25wt-%Cr, 0.4wt-%C and 1.6wt-%Ti were cast and subjected to metallographic characterisation before and after exposure for 70 h in air at 1250°C, the highest temperature at which these alloys may be used under low applied stresses. The alloys based mainly on nickel contain principally chromium carbides while TiC is the principal carbide phase in the alloys mainly based on cobalt. The oxidation resistance is the best for the alloys richer in nickel than in cobalt, but titanium has the same effect for all alloys, whatever the base element: after oxidation it is present as an external TiO2 layer covering chromia. The presence of this outermost more (Ni-based alloys) or less thick (Co-based alloys) TiO2 scale on the outer face of the external chromia scale, is expected to have a protective role against chromia volatilisation, phenomenon which can be very important at so high temperature. [ABSTRACT FROM AUTHOR]

In this paper, the performance of hardsurfacing Cobalt alloy (Stellite 6) and Nickel alloy (Colmonoy 88) was tested in tribological slurry conditions by using a pot tester. Thermal spraying powders were deposited on AISI 316L substrates by using a high-velocity oxy-fuel (HVOF) technique. Wear experiments are carried out using a lab-scale pot tester at low velocities like 1.81, 2.71, 3.61, and 4.59 m/s. The high mass flux of ashes (ranging 30–60 wt%) is used to produce severe accelerated conditions. The effect of the size fraction of eroding particles was evaluated by preparing the multi-sized slurries of size fractions (ASTM: −200, −140 + 200, −100 + 140, and −60 + 100). Results show that the microhardness of AISI 316L was improved by the HVOF depositing of Cobalt alloy-6 and Nickel alloy-88. The average surface microhardness of Cobalt alloy-6 was found lower (439 ± 19 HV 1000) than the Nickel alloy-88 coating (601 ± 11 HV 1000). Erosion performance of coatings was found to be increased with an increase in the value of the velocity, time, mass flux, and weighted mean size of eroding particles. Results show that the Ni-alloy improved the wear resistance of AISI 316L by 2.03 ± 0.021 times in fly ash slurry conditions and 3.21 ± 0.035 times in bottom ash slurry conditions. However, the Co-alloy was beneficial in reducing the wear of AISI 316L by 1.48 ± 0.019 times in fly ash and 2.50 ± 0.032 times in bottom ash slurry conditions. Moreover, the maximum wear of AISI 316L steel was observed at an impingement angle of 30° whereas 60° and 45° for Ni-alloy and Co-alloy coatings respectively in fly ash conditions. Although, the AISI 316L and Ni-alloy coating show maximum wear at the same impingement conditions under the bottom ash slurry conditions. However, the Co-alloy coating showed maximum wear at 60° in bottom ash slurry conditions. [ABSTRACT FROM AUTHOR]

A new design of the PTA torch (PTA torch) for surfacing of nickel, cobalt and iron-based alloys was developed. It combines two systems of powder feeding into the arc: the internal and external one. Such a combination expands the technological capabilities of the PTA torch, and allows surfacing magnetic and nonmagnetic materials. These systems can be used both separately from each other and together for surfacing composite alloys with separate feeding of the matrix and reinforcing powder material. In order to increase the efficiency of powder heating at external feeding into the PTA torch, an auxiliary stabilizing gas flow is used, which allows reducing the powder losses by 10–15 % and improving the deposited bead formation. Optimal flow rates of stabilizing gas are 4‒5 l/min. The PTA torch effectively operates in the current range of 50‒300 А. [ABSTRACT FROM AUTHOR]

A new design of the PTA torch (PTA torch) for surfacing of nickel, cobalt and iron-based alloys was developed. It combines two systems of powder feeding into the arc: the internal and external one. Such a combination expands the technological capabilities of the PTA torch, and allows surfacing magnetic and nonmagnetic materials. These systems can be used both separately from each other and together for surfacing composite alloys with separate feeding of the matrix and reinforcing powder material. In order to increase the efficiency of powder heating at external feeding into the PTA torch, an auxiliary stabilizing gas flow is used, which allows reducing the powder losses by 10-15 % and improving the deposited bead formation. Optimal flow rates of stabilizing gas are 4-5 l/min. The PTA torch effectively operates in the current range of 50-300 A. [ABSTRACT FROM AUTHOR]

To select and optimize the experimental conditions for producing powders from wear-resistant cobalt alloys, the following methods were tested: gas spraying of the KhTN-37 alloy, centrifugal spraying of the KhTN-61 alloy, cryogenic spraying of the KhTN-61 alloy, and ultrasonic plasma atomization of the KhTN-62 alloy melt. The production of particles in different sizes and shapes, the difference between the experimental values of their sizes, and the potential of using individual size fractions taking into account the industrial production requirements were analyzed and summarized. The gas spraying method used for the KhTN-37 alloy did not yield the required amount of suitable powder and was thus inexpedient. The centrifugal spraying method for the production of KhTN-61 alloy powders was characterized by a significant number of spherical/needle particles formed in the sprayed material, affecting its flowability and complicating sieving. In addition, this method did not reliably protect the sprayed material against oxygen. The cryogenic spraying process for producing KhTN-61 alloy powders turned out to be unsuitable because it changed the chemical composition. The method involving melt ultrasonic atomization turned out to be the most acceptable for producing KhTN-62 alloy powders. It yielded a fine spherical powder with the required particle size. The use of this rapidly hardened powder is promising for the development of wear- and oxidation-resistant surface layers on responsible components of friction units in power equipment, particularly in aircraft structures. The high-temperature wear-resistant alloy powders can be recommended for strengthening and restoring the surfaces of components in friction units in aviation equipment and for additive manufacturing of bulk parts (3D printing), possessing high wear resistance at elevated temperatures. [ABSTRACT FROM AUTHOR]

Copyright of Atomic Energy Science & Technology is the property of Editorial Board of Atomic Energy Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, crystalline Co2B powder production was carried out by a one-step carbothermal reduction method starting from cheap, easily accessible oxide-based materials. Firstly, to determine the carbothermic CoxB formation conditions, the decomposition temperatures of the raw materials were analysed by TG/DTA, and the temperature-varying Gibbs free energies of the expected reactions were calculated. Then, Co2B production was carried out at constant CoO/B2O3/C (3.22/1.5/1.3) weight ratios at temperature (1273-1473 K) and time (30-270 min). Scanning electron microscopy (SEM), X-ray diffraction (XRD), and vibrating sample magnetometer (VSM) were used to characterize the particles. XRD results showed that reaction temperature and time are the primary control on CoxB formation and singlephase crystalline Co2B particles with crystallite sizes of 88 nm were successfully produced at 1473 K and 150 min. The permanent magnetization, saturation magnetization, and coercivity values of Co2B particles were defined as 16.58 Oe, 35.361 emu/g, 0.501 emu/g, respectively. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) is a disruptive technology which continues to challenge conventional manufacturing methods. New generations of materials for metal AM are sought to enable components with new functionalities and to save costs. However, many within the AM industry are primarily focused on metal alloys such as titanium alloys, cobalt alloys, nickel superalloys, aluminum alloys or stainless steels. This article presents a detailed overview of emerging non‐ferrous metals in the AM industry and their recent development. The potential and challenges of these materials and their adoption by AM are highlighted and compared to those of conventional materials. Furthermore, qualification pathways and supply issues for newly developed materials are discussed. This perspective is based on literature review and a thorough analysis of the metal AM industry. [ABSTRACT FROM AUTHOR]

The mechanical and chemical behaviors of cast cobalt-base superalloys are governed by the carbides and by a reactive element, which is often chromium. The content of this later element, which is efficient in resisting hot oxidation and also hot corrosion, may have consequences on the melting temperature, microstructure, and mechanical properties at high temperatures and at room temperature. Seemingly, the effect of chromium content on the microstructure and properties of cast equi-axed Co-Cr-Ta-C superalloys containing TaC as single reinforcing carbide and in high-enough quantities to achieve a high level of creep resistance has not been the subject of previous investigations. The present work is devoted to the exploration of this influence of Cr content on the as-cast microstructure of a model alloy in this category, as well as on its microstructure transformations at high temperatures. The work aims to help rate the Cr content to achieve the best characteristics in machinability and high-temperature properties. This is of great importance for fabricability (production cost) and sustainability in service (long enough lifetime performance). A series of six alloys derived from a rather well-known alloy and presenting various Cr contents were thus elaborated by casting. Their microstructures were investigated in their as-cast state as well as in an aged state resulting from a 4-day stage at 1400 K. Vickers indentation was also carried out to study how hardness may evolve with Cr content. It was seen that the higher the Cr content, the lower the solidus temperature, the coarser the TaC population, the harder the alloy, and the higher the risk of brittleness. In order to reach the best compromise, the preferred Cr weight content range, as identified by this work, is 20–30%; indeed, for such Cr contents: (1) the matrix is austenitic, then dense, and then hard and not brittle, and thus is mechanically resistant and tough; (2) the TaC carbides are script-shaped and resistant against morphology changes at high temperatures, and thus efficiently preserve interdendritic cohesion for a long time, and, consequently, (3) the alloys are machinable, have expected good toughness, and can be resistant against creep deformation as well as oxidation and corrosion at high temperatures thanks to the Cr content, allowing for chromium-forming behavior.

Oxide-dispersion-strengthened (ODS) alloys have long been considered for high temperature turbine, spacecraft, and nuclear reactor components due to their high temperature strength and radiation resistance. Conventional synthesis approaches of ODS alloys involve ball milling of powders and consolidation. In this work, a process-synergistic approach is used to introduce oxide particles during laser powder bed fusion (LPBF). Chromium (III) oxide (Cr2O3) powders are blended with a cobalt-based alloy, Mar-M 509, and exposed to laser irradiation, resulting in reduction–oxidation reactions involving metal (Ta, Ti, Zr) ions from the metal matrix to form mixed oxides of increased thermodynamic stability. A microstructure analysis indicates the formation of nanoscale spherical mixed oxide particles as well as large agglomerates with internal cracks. Chemical analyses confirm the presence of Ta, Ti, and Zr in agglomerated oxides, but primarily Zr in the nanoscale oxides. Mechanical testing reveals that agglomerate particle cracking is detrimental to tensile ductility compared to the base alloy, suggesting the need for improved processing methods to break up oxide particle clusters and promote their uniform dispersion during laser exposure. [ABSTRACT FROM AUTHOR]

Hardmetals (or cemented carbides) were invented a hundred years ago and became one of the most important materials in engineering. The unique conjunction of fracture toughness, abrasion resistance and hardness makes WC-Co cemented carbides irreplaceable for numerous applications. As a rule, the WC crystallites in the sintered WC-Co hardmetals are perfectly faceted and possess a truncated trigonal prism shape. However, the so-called faceting–roughening phase transition can force the flat (faceted) surfaces or interfaces to become curved. In this review, we analyze how different factors can influence the (faceted) shape of WC crystallites in the cemented carbides. Among these factors are the modification of fabrication parameters of usual WC-Co cemented carbides; alloying of conventional cobalt binder using various metals; alloying of cobalt binder using nitrides, borides, carbides, silicides, oxides; and substitution of cobalt with other binders, including high entropy alloys (HEAs). The faceting–roughening phase transition of WC/binder interfaces and its influence on the properties of cemented carbides is also discussed. In particular, the increase in the hardness and fracture toughness of cemented carbides correlates with transition of WC crystallites from a faceted to a rounded shape. [ABSTRACT FROM AUTHOR]

The hardness of heat (thermally) treated CoCrMo ingots, recycled by electron beam melting and refining (EBMR) of a technogenic CoCrMo material (waste from the dental technology) under different process conditions (temperature and residence time) is examined. The heat treatment consists of two-step heating up to temperatures of 423 K and 1343 K and retention times of 40 and 60 min, respectively. The influence of various loads (0.98 N, 1.96 N, 2.94 N, 4.9 N, and 9.8 N) on the hardness of the CoCrMo alloy, recycled by EBMR, before and after heat treatment is studied. It has been found that regardless of the EBMR process conditions, the obtained samples after heat treatment have similar hardness values (between 494.2 HV and 505.9 HV) and they are significantly lower than the hardness of the specimens before the heat treatment. The highest hardness (600 HV) is measured in the alloy recycled at 1845 K refining temperature for 20 min. This is due to the smaller crystal structure of the resulting alloy and the higher cobalt content. The results obtained show that the heat treatment leads to considerable changes in the microstructure of the CoCrMo ingots recycled by EBMR. With the increase of the e-beam refining temperature, after the heat treatment, the grains' size increases and the grains' shape indicates an incomplete phase transition from γ-fcc to ε-hcp phase. This leads to a slight increase in the hardness of the alloy. [ABSTRACT FROM AUTHOR]

Considering the thermodynamic stability of various hydrides, a strategy has been employed to improve the hydrogen isotope storage properties of ZrCo alloy which involves partial co-substitution of Zr with Ti and Nb. Herein, alloys of composition Zr 0.8 Ti 0.2-x Nb x Co (x = 0.05, 0.1, 0.15) is prepared, characterized and the effect of Ti and Nb doping on hydrogen storage properties of parent ZrCo alloy is investigated. XRD analysis confirmed the formation of desired pure cubic phase of all the synthesized alloys similar to ZrCo phase. The presence of a single plateau in hydrogen desorption pressure-composition isotherms confirms single step hydrogen absorption-desorption behavior in Zr 0.8 Ti 0.2-x Nb x Co alloys. The equilibrium pressure of hydrogen desorption decreases marginally with increasing Nb content in Zr 0.8 Ti 0.2-x Nb x Co alloys which is further corroborated by differential scanning calorimetry measurements. Investigation of hydrogen induced disproportionation behavior in ITER-simulating condition revealed substantial impact of co-substitution of Ti and Nb on anti-disproportionation properties of ZrCo alloy. These remarkable properties make the Ti and Nb co-substituted quaternary alloys a desirable material for hydrogen isotope storage and delivery application. [Display omitted] • Prepared Zr 0.8 Ti 0.2-x Nb x Co alloys having single cubic phase. • Hydrogen storage behavior of Zr 0.8 Ti 0.2-x Nb x Co alloys was investigated. • Substitution of Zr with Ti and Nb significantly decreases the desorption temperature. • Zr 0.8 Ti 0.05 Nb 0.15 Co alloy has remarkably high anti-disproportionation properties. [ABSTRACT FROM AUTHOR]

Six alloys (25 wt% Cr, 0.4 C, 1.6 Ti, Co and Ni (bal.)) were prepared by casting for evaluating their oxidation and creep properties at 1200°C. Their microstructures consist of a dendritic matrix with eutectic carbides in the interdendritic spaces. Carbides are TiC for the alloys richer in Co than in Ni, and chromium carbides in the alloys richer in Ni than in Co. Differential thermal analysis shows that all alloys start melting above 1250°C. The oxidation tests in air at 1200°C allow observing a chromia–forming behavior of the alloys rich in nickel better than the cobalt alloys. In contrast, the creep resistance tests at 1200°C demonstrate an undeniable superiority of the alloys rich in cobalt. Good compromise for both types of high temperature behavior appears to be obtained by a Co-base alloy containing nickel as minor element but with significant proportion in nickel (15–30 wt% Ni). [ABSTRACT FROM AUTHOR]

Hybrid biological-inorganic (HBI) systems comprising inorganic water-splitting catalysts and aerobic hydrogen-oxidizing bacteria (HOB) have previously been used for CO 2 conversion. In order to identify new biocatalysts for CO 2 conversion, the present study used an HBI system to enrich HOB directly from environmental samples. Three sediment samples (from a brackish water pond, a beach, and a tide pool) and two activated sludge samples (from two separate sewage plants) were inoculated into HBI systems using a cobalt phosphorus (Co–P) alloy and cobalt phosphate (CoPi) as inorganic catalysts with a fixed voltage of 2.0 V. The gas composition of the reactor headspaces and electric current were monitored. An aliquot of the reactor medium was transferred to a new reactor when significant consumption of H 2 and CO 2 was detected. This process was repeated twice (with three reactors in operation for each sample) to enrich HOB. Increased biomass concomitant with increased H 2 and CO 2 consumption was observed in the third reactor, indicating enrichment of HOB. 16S rRNA gene amplicon sequencing demonstrated enrichment of sequences related to HOB (including bacteria from Mycobacterium , Hydrogenophaga , and Xanthobacter genera) over successive sub-cultures. Finally, four different HOB belonging to the Mycobacterium , Hydrogenophaga , Xanthobacter , and Acidovorax genera were isolated from reactor media, representing potential candidates as HBI system biocatalysts. [ABSTRACT FROM AUTHOR]

Tribological coatings play a key role in enhancing the performance and service life of engineering systems and components. Over the years, DMRL has worked extensively in studying various aspects of tribological coatings used in aerospace and missile propulsion systems where harsh and hostile environments prevail. The coatings have been deposited mostly by thermal spray processes for these applications. The studies have been done to understand the relationship between microstructure, mechanical properties and tribological behaviour of coatings. In this work, a cermet coating based on carbide to resist wear and an abradable coating based on cobalt alloy to control clearance between the blade tip and shroud for gas turbine aeroengine application and a low friction coating developed for a missile application will be discussed. [ABSTRACT FROM AUTHOR]