Cobalt Alloy Research Articles

Effect of Co Content and Temperature on Shear Mechanical Properties of Nano‐Polycrystalline Ni–Co Alloy

Herein, the effects of different Co content and temperature factors on the shear mechanical properties of nano‐polycrystalline nickel–cobalt alloy are analyzed by molecular dynamics (MD) simulations. It is found in the work that the highest shear modulus of 63.03 GPa is obtained when the Co content is 10%, attributed to the lattice distortion caused by the difference in the lattice parameters between two elements. During the shearing process, the multilevel twins are present with intensification of the deformation process, resulting in excellent dynamic shear performance. Shockley dislocations will drive the stacking faults and other partial dislocations to constitute a tetrahedral edge, and finally forms a tetrahedral structure. In addition, as the temperature of the shear environment increases, the highest strain and stress decrease. The grain boundary atoms increase significantly, and the atoms inside the grains decrease accordingly. As the degree of atomic disorder increases, the grain boundaries will melt gradually. The decrease of partial dislocation density can weaken the entanglement effect caused by dislocations. The previous conclusions promote the product development and application of nano‐polycrystalline alloys in the future, and provide important guidance significant for the engineering application of nickel–cobalt alloys.

Wear and corrosion behaviour of nanocrystalline TaN, ZrN, and TaZrN coatings deposited on biomedical grade CoCrMo alloy

TaZrN coatings were synthesized directly on biomedical grade CoCrMo using radio-frequency magnetron co-sputtering. The mechanical properties, adhesion, wear, and corrosion resistance of the TaZrN coatings on the Cobalt alloy were assessed to determine their potential for hip joint replacement applications. The results indicate the TaZrN coatings are highly adhesive and have a nanocrystalline structure with a Hardness and Young’s modulus of 19 GPa and 297 GPa, respectively. The TaZrN coatings showed a 3% lower wear rate of the polyethylene counterpart and an icorr value 274 times lower than the uncoated CoCrMo alloy. The excellent wear and corrosion resistance of the TaZrN coating suggest that it is a promising coating material for CoCrMo alloy to improve the lifetime of hip joint implants.

Electrocatalytic determination of hydrazine concentrations with polyelectrolyte supported AuCo nanoparticles on carbon electrodes

Gold–cobalt alloy nanoparticles (AuCo NPs) deposited on a screen-printed carbon electrode (SPCE) surface modified with a combination of polystyrene sulfonate (PSS) and poly-3,4-ethylenedioxythiophene (PEDOT) is demonstrated for monitoring the direct oxidation of hydrazine. The surface morphology and properties of PSS:PEDOT supported AuCo NPs modified carbon electrodes were characterized using field-emission scanning electron microscopy, X-ray diffraction, and energy dispersive spectroscopic analysis. The current change with respect to the electrocatalytic oxidation of hydrazine on AuCo NPs/PSS:PEDOT/SPCE was used for the quantitative analysis in conjunction with cyclic, linear sweep, and differential pulse voltammetries alongside chronoamperometry (CA). The voltammetric response for the oxidation of hydrazine using AuCo NPs/PSS:PEDOT/SPCE was also compared with those of bare SPCE and PSS:PEDOT/SPCE. Under optimum conditions using CA, the modified electrode offered a linear range from 0.5 to 1000 μM, a sensitivity of 1.64 µA µM−1 and a limit of detection of 0.17 µM. The stability, reproducibility, sensitivity, and selectivity were also investigated. Finally, the AuCo NPs/PSS:PEDOT/SPCE platform was employed to determine native hydrazine concentrations in local river water samples.

Materials Matter

Iron cobalt (FeCo) alloys advance battery electric vehicle performance with increased power and torque as well as smaller motor size and greater efficiency

Electrochemical Dissolution of WC-Co Micro-Tool in Micro-WECM Using an Eco-Friendly Citric Acid Mixed NaNO3 Electrolyte

The present study analyzes the efficient electrochemical dissolution of tungsten carbide–cobalt alloy (WC-Co) micro-tools for micromachining operations with an eco-friendly electrolyte. One of the essential factors in efficient anodic dissolution is the selection of appropriate electrolytes. Sulphuric acid (H2SO4) is extensively used in the electrochemical process to dissolve WC-Co due to its higher dissolution rate and efficiency. But toxicity of H2SO4, even at moderate concentration, poses a significant threat to the operator and the environment. Hence in this investigation, an eco-friendly electrolyte has been proposed which is a combination of sodium nitrate (NaNO3) and a complexing agent citric acid (C6H8O7), that not only gives a higher dissolution rate of WC-Co but also gives similar dissolution efficiency that of H2SO4. A detailed experimentation to optimize the concentration of complexing agent in the eco- friendly electrolyte was carried out through micro wire-electrochemical machining (micro-WECM) and was analyzed using yield parameters, topographical and material surface analysis as well as electrochemical analysis. This eco-friendly electrolyte produces higher dissolution rate and better surface finish in different levels of parameters in comparison to H2SO4. Potentiodynamic polarization test through linear sweep voltammetry (LSV) showed maximum current density for WC-Co alloy in the proposed eco-friendly electrolyte.

Numerical Simulation and Defect Identification in the Casting of Co-Cr Alloy

The development of biomaterials, particularly metallic ones, is one of the focuses of the scientific community, mainly due to an increase of average life expectancy and an improvement of the casted materials combined with better mechanical properties and defect-free products. The use of cobalt alloys in applications, such as knee, hip, and dental prostheses, is the result of their good ability to maintain mechanical properties and biocompatibility over long periods of use. Numerical methods are becoming more important, as they help product improvement in a faster and economic way. This work focuses on the development of a numerical model in ProCAST®, comparing the shrinkage porosity and cooling curves with real castings. When correlating simulation results with available experimental data, it is possible to understand that the formulated model demonstrates an acceptable solution in terms of precision (shrinkage porosity and cooling curve). The alloy’s thermal properties and heat conditions were iteratively changed until the developed numerical model turned out a viable tool for this specific alloy when used in the investment casting process.

Influence of Preheating Temperature on Structural and Mechanical Properties of a Laser-Welded MMC Cobalt Based Coating Reinforced by TiC and PCD Particles.

This article presents research on the structural and mechanical properties of an innovative metal matrix composite (MMC) coating designed for use in conditions of intense metal-mineral abrasive wear. The layer, which is intended to protect the working surface of drilling tools used in the oil and natural gas extraction sector, was padded using the multi-run technique on a sheet made of AISI 4715 low-alloy structural steel by Laser Direct Metal Deposition (LDMD) using a high-power fiber laser (FL). An innovative cobalt alloy matrix powder with a ceramic reinforcement of crushed titanium carbide (TiC) and tungsten-coated synthetic polycrystalline diamond (PCD) was used as the surfacing material. The influence of the preheating temperature of the base material on the susceptibility to cracking and abrasive wear of the composite coating was assessed. The structural properties of the coating were characterized by using methods such as optical microscopy, scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), transmission electron microscopy (TEM) and X-ray diffraction analysis (XRD). The mechanical properties of the hardfaced coating were assessed on the basis of the results of a metal-mineral abrasive wear resistance test, hardness measurement, and the observation of the abrasion area with a scanning laser microscope. The results of laboratory tests showed a slight dissolution of the tungsten coating protecting the synthetic PCD particles and the transfer of its components into the metallic matrix of the composite. Moreover, it was proved that an increase in the preheating temperature of the base material prior to welding has a positive effect on reducing the susceptibility of the coating to cracking, reducing the porosity of the metal deposit and increasing the resistance to abrasive wear.

Synergistic effect of NiCo alloy and NiCoS integrated with N doped carbon for superior rate and ultralong-lifespan lithium sulfur batteries

The transition-metal-based alloy and chalcogenides have been widely investigated as efficient sulfur host for lithium sulfur batteries (LSB), yet the synergistic effect of both has been rarely reported. Herein, nickel cobalt alloy (NiCo) and nickel cobalt sulfides (NiCoS) have been simultaneously constructed on the nitrogen-doped carbon substrate (NiCo-NiCoS/NC) via facile calcination-sulfurization of NiCo Prussian blue analogue (NiCo-PBA). The abundantly exposed NiCo alloy and NiCoS domains act as adsorption and catalytic sites that enable effective capture and catalytic conversion of polysulfides, and the highly conductive NiCo-NiCoS integrated with N-doped carbon provides a facile Li+ transfer channel. As a result, S@NiCo-NiCoS/NC electrode delivers a high initial discharge capacity of 1345.1 mA h g−1 at the current density of 0.1 C, superior rate capability of 692.1 mA h g−1 up to 5 C, and ultralong lifespan over 1500 cycles with a small capacity decay of 0.055% per cycle at the current density of 1.0 C.

Method of Using the Correlation between the Surface Roughness of Metallic Materials and the Sound Generated during the Controlled Machining Process.

The article aims to use the generated sound as operational information needed for adaptive control of the metalworking process and early monitoring and diagnosis of the condition of the machined materials using a newly introduced surface roughness quality index due to the sound-controlled machining process. The object of the measurement was correlation between the sound intensity generated during cutting and the material parameters of the machined surface, i.e., the roughness of the machined surface and the degree of wear of the cutting tool. The roughness was measured during longitudinal turning of a steel billet with a P25 insert made of 12X18H10T steel and a T15K6 cutting insert made of a titanium, cobalt, and tungsten group alloy. The correlation between the sound and roughness of the machined surface was 0.93, whereas between the sound and wear of the cutting tool was 0.93. The correlation between sound and tool wear in the experiment with P25 and T15K6 cutting inserts and the correlation between sound and roughness is positive.

Density and excess volumes of liquid copper, cobalt, iron and their binary and ternary alloys

Abstract The densities of liquid copper, cobalt, and iron, their binary and ternary alloys have been measured over a temperature range including the undercooled regime. A non-contact technique was used, consisting of electromagnetic levitation combined with optical dilatometry. For all samples, the density was a linear function of temperature. The concentration dependence was studied by means of the excess volume which was negligible for Co– Fe and positive for Cu– Fe, Cu– Co, and Cu–Co – Fe. The density of the ternary alloy could be predicted from the excess volumes of the binary phases without the need to introduce any ternary interactions.

A review of electrical discharge machining on various superalloys

• This work presents review of the work done in the field of the EDM machining in the recent past, basically deals with the EDM machining of Superalloys. • Study of various parameters during the machining. • The effect of dielectric fluids during the machining was observed. • Research gaps were observed, materials still to be explored for the parameters research during EDM machining. • The conclusions of this investigation were found to be consistent with available literature. Superalloys are a group of nickel, iron–nickel and cobalt alloys used in various applications. These metals have excellent heat resistant properties and retain their stiffness, strength, toughness and dimensional stability at temperatures much higher than the other aerospace structural materials hence are also known as metal of future. This paper reviews the EDM machining superalloys like Nickel-based superalloys, Cobalt-based superalloys, iron based superalloy also the effect of parameters on MRR, EWR, and surface roughness. The study suggest that current and pulse on time were the most influential parameters, current below 1 A with changing polarity are more effective. Polarity also plays an important role in deciding MRR.

Observation of wear scars of the tool alloys for friction stir welding using transmission electron microscope

Friction stir welding (FSW) is a joining method which uses the frictional heat generation between a rotating tool and joining metals. Furthermore, cracks, residual stresses and distortions which are the problems of the conventional welding do not occur because FSW works in the solid state 1). Cobalt alloys which have high durability in high temperature are used for the FSW tool material when it is predicted breaking. However, Cobalt alloy tools were worn compared with steel tools in our previous study. Then we carried out reciprocating wear test as first stage and observed the under structure of wear scar using TEM to clear the wear mechanism of FSW tool alloy.

Applications of cooling and lubrication nozzles in grinding, milling, and turning: A review emphasising nozzle design, location and orientation

Cooling systems in standard machining operations play an essential role in achieving the quality and performance required in operational outcomes. Most machining operations, and especially those dealing with refractory materials such as nickel, cobalt, and titanium-based alloys, cannot be conducted efficiently without the application of cooling. Cooling nozzles are important elements of cooling systems and control the flow rates of coolants as well as their direction. The design of the nozzle may significantly influence the efficiency of cooling systems, where high coolant consumption is one of their main ecological and economic drawbacks and poor nozzle design may result in the dissipation of coolant in an inefficient manner. This paper reviews state-of-the-art cooling systems used for machining, with an emphasis on the designs and applications of cooling nozzles used for grinding, milling, and turning operations. The first part of the paper considersrecent publications concerning common types of cooling systems as well as the nozzle designs and applications used, and also summarises the advantages and disadvantages of each system. The second part briefly discusses important research studies of the design, location and orientation of cooling nozzles. Finally, conclusions are drawn that represent the most significant results and findings of this review, the main objective of which is to fill the research gap identified with regard to the development of cooling and lubrication nozzles and their applications during grinding, milling, and turning processes.

Tensile and flexural characteristic of functionally graded carbon fiber reinforced composites with alumina and yttria stabilized zirconia fillers for bone implant

Bone fractures are a common form of injury with more than 10 million cases per year in India. The vivo treatment of bone fractures is done with a surgical bone plate attached to the site of fracture. The bone plate attached to the injured bone facilitates the load bearing and helps in the healing of bones. Commonly stainless steel, titanium alloys and chromium cobalt alloys are used as the materials for these implants. They have the disadvantage of stress shielding the bone and having differing elastic modulus from the bone which causes reduction in bone density and implant loosening, respectively. This problem can be reduced using bone implant that have mechanical properties like the bone. The bone is a natural functionally graded material with varying mechanical properties from the surface to the core of the bone. So, a functionally graded material concept can be used instead of conventional metal or metal alloys for the bone plates. The gradation is done in a carbon fiber reinforcement polymer matrix with alumina and yttria-stabilized zirconia as particulate filler. Mechanical testing has shown that carbon fiber reinforced polymer composite with YSZ as particulate filler exhibits the best properties that are suitable for use as implants.

A rhodium–cobalt alloy bimetallene towards liquid C1 molecule electrooxidation in alkaline media

Rh–Co ABM is synthesized by the cyanogel self-reduction strategy and exhibits high activity for C1 molecule electrooxidation.

Magnetic Vortex Domain Wall Observation on Polycrystalline Imperfect Iron−Cobalt Alloy Nanowires Growing on 1050 Aluminum

Herein, the magnetic vortex domain wall structure of polycrystalline imperfect iron−cobalt alloy nanowires (Nws) growing on 1050 aluminum by pulsed electrodeposition is reported. The magnetic properties are analyzed using magnetometry and off‐axis electron holography. The electrodeposited Nw arrays show homogeneous elemental composition and exhibit a structure composed of piled‐up grains of small crystallites. The saturation magnetization, coercive field, and reduced remanence, measured in directions parallel and perpendicular to the Nw's axis, are studied as a function of the temperature. Although the array of Nws on anodized aluminum grows both straight and within an inclination angle, in both cases, a high shape anisotropy is noticed, which is the most predominant contribution to the magnetic behavior. Misalignments and defects of the Nws in the array, as well as the wide distribution of lengths and diameters, do not contribute significantly to coercivity dispersion. A modified model is used to explain the changes in the magnetic behavior of the Nw's arrays, which accounts for structural imperfections and magnetostatic interactions. The reversal magnetization arising from the vortex domain wall propagation via localized curling is verified by off‐axis electron holography.

Modelling of cutting forces and surface roughness evolutions during straight turning of Stellite 6 material based on response surface methodology, artificial neural networks and support vector machine approaches

The present research work proposes an experimental investigation helping to comprehend fundamental impacts of operating conditions during the cutting of cobalt alloys (Stellite 6). Thus, an experimental design was adopted to allow to build predicted mathematical models for the outputs, which are the average peak-to-valley profile roughness (Rz) and the tangential cutting force (Ft). Artificial neural network (ANN), support vector machine (SVM) and response surface methodology (RSM) were exploited to model the pre-cited outputs according to operation parameters. As a result, it has been highlighted that both feed rate and cutting depth, considerably, affect tangential cutting force evolution. Moreover, results show that both the insert feed rate and nose radius, are higher. This means the average peak-to-valley profile roughness is higher. In order to put out the effect of operating parameters on cutting outputs, Analysis of variance (ANOVA) method has been employed. This has allowed the detection of significant cutting conditions affecting average peak-to-valley profile roughness and tangential cutting force. In fact, to highlight the performance of adopted mathematical approaches, a comparison between RSM, ANN, and SVM has been also established in this study.

Lithiophilic 3D Copper‐Based Magnetic Current Collector for Lithium‐Free Anode to Realize Deep Lithium Deposition

AbstractLithium metal is the ideal anode material for high‐energy‐density lithium‐based batteries. Nevertheless, lithium metal tends to accumulate on the surface of the current collector during the plating and stripping process to form lithium dendrites, resulting in low Coulombic efficiency and safety issues. Here, a lithiophilic 3D copper‐based magnetic current collector is designed by loading ferromagnetic nickel–cobalt alloy and lithiophilic zinc oxide onto the copper foam to create a lithium‐free anode. Under the micromagnetic field, the novel lithium‐free anode achieves a high level of deep lithium deposition (from 300 µm to about 1000 µm), successfully alleviating the large change of lithium volume. In addition, the Coulombic efficiency and cyclic stability are improved effectively. With a total capacity of 1 mA h cm−2 at a current density of 1 mA cm−2, the Coulombic efficiency of the above remains 95% at 590th‐cycle. Moreover, the symmetric cell can stably cycle for more than 560 h at 2 mA cm−2 with the capacity of 1 mA h cm−2. This novel strategy will potentially open up new horizons for lithium‐free anodes, which may be generalized to other advanced energy storage systems.

Crack behaviour at the interface of a surface layer applied on a steel substrate by laser cladding

An influence of the bi-material interface between a steel substrate and a thin protective layer applied through laser cladding was investigated. A range of elastic properties and thicknesses of the layer were considered to cover the behaviour of a short crack in the selected materials such as bronze, nickel or cobalt alloys. The special case of the crack terminating directly at the interface was investigated, which is connected to the necessity of application of generalized approaches of linear elastic fracture mechanics. The results contribute to better understanding of fracture response of selected materials and to a more reliable decision on choosing a proper material of the protective layer.

Wear and corrosion characteristics of nano-crystalline tantalum nitride coatings deposited on CoCrMo alloy for hip joint applications

Osteolysis is the resorption or removal of bone tissue, which is associated with the accumulation of polyethylene particles and misalignment of hip joint implant components. The mechanical properties, adhesion, tribological, and corrosive properties of single-layered tantalum nitride (TaN) coatings on biomedical grade cobalt alloy were evaluated to determine the potential of these coatings to prevent osteolysis in hip joint replacement applications. The TaN coatings were deposited directly on biomedical grade CoCrMo alloy disks using a hybrid system of Plasma Enhanced Chemical Vapor Deposition (PECVD) and Physical Vapor Deposition (PVD) at different deposition temperatures. By increasing the deposition temperature from 350 °C to 500 °C, the mechanical properties and adhesion improved remarkably, without a significant change in the crystal structure according to XRD and XPS results. The ball-on-disk wear testing results showed that the wear rate of the polyethylene balls decreased by 5% when sliding against the TaN-500C sample compared to sliding against the uncoated alloy and was 23% lower than the TaN-350C sample. The electrochemical corrosion results indicated that the TaN coating deposited at 500 °C is about 15% more noble than the uncoated alloy, which allows the rapid formation of a protective passive layer. These results suggest that TaN is a promising coating for CoCrMo alloy to improve the lifetime of hip joint implants.