Nickel-chromium Alloy Research Articles

Design and fabrication of nickel-chromium reinforced 2-stage energy efficient pyrolysis reactor for waste plastics applications

ABSTRACTThis paper focuses on the design and fabrication of a two-stage energy-efficient plastic waste reactor, which is capable of melting the various types of waste plastics such as HDPE, LDPE, PS, PVC, PET, PVC, PP, and in the melting temperature in the range of 400 οC to 1000 οC. The methodology involved in this experimental process is a superalloy with a nickel-chromium alloy percentage composition of 15CR85S for the reactor and 20CR80S for the furnace part. The plasma arc welding process is applied in the temperature range 10000 οC with a coating thickness of 75 microns over the materials, followed by 15CR85S-75μm YSZ. 20CR80S-75μm YSZ and 15NI85S-75 μm YSZ. The salt spraying technique is employed in this analysis. The potential benefits of this experimental process is that a reactor made up of 15CR85S-75μm YSZ gives promising results of lesser thermal expansion in the range of 10 K−1 × 10−6 for 15CR85S-75μm YSZ for uncoated 13K−1×10−6, Which 15CR85S-75μm YSZ material is 23% superior to uncoated materials. The crack porosity of 20CR80S-75μm YSZ is excellent in the order of 400 × 10−6, and for uncoated material, it is located in the order of 600 × 10−6. 20CR80S-75μm YSZ material is 50 % superior to uncoated materials.

Расчет и конструирование нагревательной печи для правки экспериментальных образцов судовых валов

During operation the shafts of responsible purpose, which have received a curvature of the longitudinal axis and are not allowed for further operation, are subjected to correction with heating. The following heating methods are considered: with the use of a gas burner, induction heating, as well as tubular resistance furnaces. The use of a gas burner causes difficulties in the heating process controlling and the appearance of defects due to uneven heating afterwards. The diagram of the device for heating the shaft with a gas burner is illustrated. The scheme of induction heating of the shaft section is considered. During induction heating, it is necessary to use special equipment. It is proposed to use a tubular resistance furnace in an experimental study. The requirements for the material of the heating element are considered. A wire made of chromium-nickel alloy nichrome H20N80 for the heating element was selected. The layout of the tubular resistance furnace was made and materials were selected. The design of a resistance furnace for insulated windings is presented. Calculations of the length, diameter and number of turns of the heating element are performed. After manufacturing, a test heating of the sample was carried out. It is concluded that the furnace power was sufficient to warm up the sample to the required temperature of 650 °C for three hours.

Research Paper: Effect of Metal primer and Adhesives on Bond Strength of Composite Resin to Nickel-chromium Alloy

Introduction: Indirect metal-ceramic restorations can be repaired intra-orally by using composite resins. The purpose of this study was to evaluate the effect of several adhesives and metal primer on shear bond strength(SBS)of flowable composite to nickel-chromium(Ni-Cr) alloy. Materials and Methods: In this in vitro study, 100 Ni-Cr alloy specimens were casted measuring 2x10x8 mm. The surface of all specimens was sandblasted, and they were randomly assigned to five groups (n=20) of no primer or adhesive (group 1 or control),alloy primer (AP; group 2), AP+Single Bond 2 (SB2) adhesive (group 3),AP+G-Premio Bond (group 4), and G-Premio Bond alone (group 5).Flowable composite was bonded to the surfaces in cylindrical plastic molds (3 mm in diameter and height). The specimens were stored in distilled water at room temperature for 24 hours. Thermocycling was performed for 1000 cycles. The SBS was measured by a universal testing machine. Failure mode was also evaluated under a stereomicroscope. Results: The SBS of composite to alloy was the highest in G-Premio group (20.09±14.27MPa), and the lowest in the control group (11.11±5.35MPa). The failure mode in the four experimental groups was mainly mixed while the control specimens showed adhesive failure(P≤0.05). Conclusion: It maybe concluded that G-Premio universal adhesive can create a strong bond to Ni-Cr alloy.

On-demand electrically controlled melatonin release from PEDOT/SNP composite improves quality of chronic neural recording.

Long-time and high-quality signal acquisition performance from implantable electrodes is the key to establish stable and efficient brain-computer interface (BCI) connections. The chronic performance of implantable electrodes is hindered by the inflammatory response of brain tissue. In order to solve the material limitation of biological interface electrodes, we designed sulfonated silica nanoparticles (SNPs) as the dopant of Poly (3,4-ethylenedioxythiophene) (PEDOT) to modify the implantable electrodes. In this work, melatonin (MT) loaded SNPs were incorporated in PEDOT via electrochemical deposition on nickel-chromium (Ni-Cr) alloy electrode and carbon nanotube (CNT) fiber electrodes, without affecting the acute neural signal recording capacity. After coating with PEDOT/SNP-MT, the charge storage capacity of both electrodes was significantly increased, and the electrochemical impedance at 1kHz of the Ni-Cr alloy electrodes was significantly reduced, while that of the CNT electrodes was significantly increased. In addition, this study inspected the effect of electrically triggered MT release every other day on the quality and longevity of neural recording from implanted neural electrodes in rat hippocampus for 1 month. Both MT modified Ni-Cr alloy electrodes and CNT electrodes showed significantly higher spike amplitude after 26-day recording. Significantly, the histological studies showed that the number of astrocytes around the implanted Ni-Cr alloy electrodes was significantly reduced after MT release. These results demonstrate the potent outcome of PEDOT/SNP-MT treatment in improving the chronic neural recording quality possibly through its anti-inflammatory property.

The effect of repeated porcelain firings on the marginal fit of millable and conventional casting alloys.

The durability of dental restorations is highly determined by an accurate marginal fit, which is in turn affected by the high temperature of porcelain firing. Information is inadequate about the marginal adaptation of metal-ceramic restorations fabricated by soft metal milling technologies after repeated firings. This study aimed to compare the effect of repeated ceramic firings on the marginal fit of copings fabricated from cobalt-chromium through soft metal milling and a conventional nickel-chromium casting alloy. A single standard brass die was designed, machined, and scanned, based on which, 20 frameworks were designed and fabricated through either soft metal milling or conventional casting (n = 10 per group) and porcelain veneered. The vertical marginal fit of the metal copings was measured after 3, 5, and 7 firing cycles by using a digital microscope on 16 points around the finish line of the metal die at ×80 magnification. The data were analyzed through repeated measures ANOVA and independent t-test (α = 0.05). The marginal fit of neither metal group was significantly affected by the number of firing cycles (P = 0.747). However, the marginal discrepancy was statistically lower in the soft metal milling group than that in the casting group (P<0.001). Repeated porcelain firings did not significantly affect the marginal fit of either alloy and remained within the clinically acceptable range after firings. However, the milled alloy had superior marginal fit regardless of the number of firing cycles.

Effect Of Surface Treatment on The Shear Bond Strength Between Nickel-Chromium Alloy and Veneering Porcelain

Nickel–chromium (Ni–Cr) alloys, have been used widely, due to their superior physical properties and economic issues in relation to other precious alloys. Many studies have been carried out on porcelain fused to metal restorations to enhance the bonding quality of the porcelain to Ni-Cr alloy, such as mechanical treatment by air abrasion particles or chemical treatment by acid etching to increase the longevity of the restoration. The purpose of this study is to investigate the effect of surface treatments sandblasting with Aluminum Oxide (Al2O3), acid etching with Potassium hydrogen difluoride acid (KHF2) and combination treatment on the shear bond strength between Nickel-chromium alloy substructure and porcelain veneer. Twenty-one cylindrical shaped samples have base of 5 mm in diameter and 1 mm in thickness and a cylinder with 4 mm in diameter and 4 mm in length were prepared from Ni – Cr alloy. The samples were divided into 3 groups (n=7) according to surface treatment: Nickel -chromium treated with sandblasting with 50μm Al2O3 group (c), Nickel – chromium etching with KHF2 group (k), and Nickel – chromium sandblasting with 50μm Al2O3 followed with acid etching with KHF2 group (comb). Then ceramic build up (opaque, dentin, enamel, and glaze Vita VMK Master opaque, dentin, enamel, and glaze Vita VMK Master) and sintering was performed according to manufacturer's instructions and the final dimension of porcelain cylinder (4 X 4X 1) were checked with a metal gauge. All samples were subjected to shear force in a universal testing machine at cross head speed 0.5 mm/min. and recorded in MPa. The fractured samples were checked under (DIGITAL MICROSCOPE) (X50) to evaluate the mode of failure, it was adhesive, cohesive and mixed failure modes. The shear bond strength values were analyzed with one-way ANOVA and LSD. The results showed that the highest mean of shear bond strength values was in Ni – Cr combination surface treatment group (26.11 ± 1.85), while the lowest mean was for Ni- Cr acid etched group (22.02 ± 1.5) and Nic group (20.85 ± 1.5). Within the limitation of the present study, the following conclusion can be drawn: Combination surface treatment produced the highest shear bond strength between Ni – Cr surface and veneering porcelain, followed by etching with KHF2, so combination method would increase longevity of porcelain fused to metal restorations.

DEUTSCHE EDELSTAHLWERKE CRYODUR 2721

Abstract Deutsche Edelstahlwerke Cryodur 2721 is a medium-carbon, nickel-chromium alloy cold-work tool steel. This oil hardening type cold work tool steel offers a combination of high hardness, good wear resistance, high toughness, and good machinability. This datasheet provides information on composition, physical properties, microstructure, hardness, and elasticity. It also includes information on forming and heat treating. Filing Code: TS-839. Producer or source: Deutsche Edelstahlwerke Specialty Steel.

Sintered powder high-entropy target cathodes for wear-resistant coatings

Modern machine-building production equipped with high-performance mechatronic systems and numerically-controlled and adaptive control machines for blade cutting of heat-resistant chromium-nickel and titanium alloys requires increasing the operating properties of cutting tools working at high temperature-force loads in the contact zone, respectively with a significant stress-strain state of the cutting wedge. It is possible to solve the problem of increasing wear resistance and serviceability by developing and introducing new tooling material, as well as by applying wear-resistant coatings. The paper presents the results on development of technology for obtaining high-entropy target cathodes by spark plasma sintering with subsequent application of wear-resistant coatings on metal-cutting tools by both magnetron and ion-plasma methods. Samples of sintered high-entropy target cathodes of different compositions (more than fourteen) and at different modes of their sintering (depending on temperature in five modes) with their subsequent optimization and two standard sizes (20 and 80 mm) were obtained for further application of wear-resistant coatings on the magnetron unit. The authors carried out structural and phase analysis and studied physicomechanical properties of the obtained high-entropy target cathodes: density, hardness, electrical conductivity, emissivity. The possibility of obtaining high-entropy target cathodes by spark plasma sintering was confirmed experimentally, and the effect of sintering temperature on structure and properties of the sintered samples of high-entropy target cathodes was established. Dependence of physicomechanical and electrophysical parameters of target cathodes on technological modes of spark plasma sintering is shown.

First Records of Heartbeats via ECG in a Stingless Bee, Melipona flavolineata (Apidae, Meliponini), during Contention Stress Using Isoflurane as an Anesthetic.

The hemodynamic activity of Melipona flavolineata workers was evaluated during restraint stress for a period of 30 min. The observed parameters were power variation in the elapsed time, and subsequently, six periods of one second were divided and called A, B, C, D, E and F; in each period, the electrocardiographic parameters were evaluated: spike frequency, amplitude, spike intervals and spike duration. The experiment was carried out with eight worker bees of M. flavolineata, for which electrodes of a nickel-chromium alloy were made. The bees were previously anesthetized with isoflurane and properly contained and fixed in a base for stereotaxis in which the electrode was implanted. All these procedures were performed inside a Faraday cage. The results showed power oscillations during the recording, with the highest energy level being between 300 and 600 s. Spike frequency, spike amplitude, interval between spikes and spike duration parameters underwent changes during the restraint stress period. Thus, the cardiac activity of M. flavolineata can be used as a biomarker and can be used to clarify physiological issues or alterations caused by toxic agents and indicate risk factors for these animals.

BÖHLER L306 VMR

Abstract Böhler L306 VMR is a wrought, age-hardenable nickel-chromium alloy, strengthened by additions of titanium, aluminum, and carbon. It has been developed as a creep-resisting alloy for service at temperatures up to 815 °C (1500 °F). This datasheet provides information on composition, physical properties, elasticity, and tensile properties as well as creep. It also includes information on high temperature performance as well as forming and heat treating. Filing Code: Ni-785. Producer or source: voestalpine Böhler Edelstahl GmbH &amp; Co KG.

Role of Cr-doped NiO in reduction under a low concentration of H2 and CO

Nickel-chromium alloys are often utilized in high-resistance and heating metamaterials because of their passivity; however, their reducibility behavior has never been reported. Herein, Ni-Cr reduction has been conducted in H2 and CO atmospheres. Nickel oxide (NiO) catalysts were impregnated with chromium and subsequently subjected to temperature-programmed reduction (TPR) at low concentrations of CO and H2 to determine their reduction performance. The TPR profile fitting using a Gaussian function indicated the Cr-NiO reduction transformation of Cr6+→Cr3+ at temperatures below ∼300 °C for both reductant gasses. Furthermore, the addition of Cr shifted the reduction peaks to a lower temperature owing to the interaction of Cr and Ni atoms, leading to increased reducibility. The characterizations of the Cr-NiO catalyst using X-ray diffraction, Brunauer–Emmet–Teller surface area, scanning electron microscopy, and X-ray photoelectron spectroscopy (XPS) analyses demonstrated the formation of NiCrxOy alloy with increasing surface area and porosity. The kinetic analysis using the Kissinger method demonstrated the reducibility of the catalysts with a low Ea value after the addition of Cr, where an Ea value of 68.0 kJ mol−1 (NiO) decreased to 49.3 kJ mol−1 (Cr-NiO) in the H2 atmosphere and an Ea value of 95.8 kJ mol−1 (NiO) decreased to 91.9 kJ mol−1 (Cr-NiO) in the CO atmosphere. The synergistic effects between Cr and Ni contributed to the increase in catalyst active sites by the transformation of the nickel oxidation state, which demonstrated the formation of oxygen vacancies and alloys, as proven via XPS analysis.

Effects of TiC addition on the hot corrosion behavior of IN718 fabricated by laser direct metal deposition

The hot corrosion behavior and mechanism of the IN718 nickel-chromium alloy (Sample D1) and 1 wt % TiC-reinforced IN718 (Sample D2) fabricated by laser direct metal deposition (DMD) in a 75 wt % Na2SO4 + 25 wt % NaCl saturated mixed molten salt at 700 °C were studied. After a 100-h test, the weight loss ratio of Sample D1 was 2.4 times that of Sample D2, and the corrosion rate of Sample D1 was 1.5 times that of Sample D2. Chlorination, sulphidation, and oxidation, as well as a change in the acidity at the molten salt interface of the alloy, led to serious spalling of Sample D1. However, the addition of TiC refined the grains, resulting in rapid diffusion of Cr to the alloy surface and formation of a Cr2O3 protective layer at high temperatures. In addition, the diffusion of Ni, Fe, etc., was hindered by TiC particles inside the superalloy, which reduced the thickness of the hot corrosion product layer by about 26% and improved the hot corrosion resistance of Sample D2.

EVALUATION OF Zr, Ni-Cr, And Au-Ag APPLIED MATERIALS USING FEM ON PROSTHETIC CROWNS

The crown is a steady prosthesis designed to restore the functionality of a damaged tooth along, with its shape and size. They are also used to reinforce the tooth that poses long-term risk due to wide cavities and accidental injuries. The crowns are fixed using dental cement made of different materials such as porcelain cement, ceramics, etc. The present work aims to assess the mechanical properties – stiffness and strength, of the single molar crown prosthetic tooth materials to determine the efficacy of each material under typical masticatory load observed in clinical settings. To this end, the finite element method (FEM) is used to analyze the mechanical behavior of the molar crowns made of Zirconium (Zr), Nickel Chromium (Ni-Cr), and Gold alloy (Au-Ag). The crown models were created in Solidworks and exported to the ANSYS FE package. The exported three-dimensional models were subjected to varying loading conditions – vertical and oblique forces to the tooth axis under suitable displacement boundary conditions. Due to a relatively high elastic modulus, the Zr and Ni-Cr alloy exhibited a higher stress concentration and lower deformation on the crown’s intaglio surface compared to the Au-Ag alloy.

Engineering-Physical Method for Determining the Thermal Conductivity of Objects with Micrometric Thickness and a Complex Structure

Introduction. The application of functional coatings on products, the performance properties of which are localized in the surface layer is a trend in modern mechanical engineering and materials science. The issues considered in this regard are relevant, in particular, for thermal-barrier coatings of turbine blades of steam and gas turbine engines. It is worth mentioning the materials that experience significant thermal loads during operation. In this case, the lack of reliable methods for predicting the thermophysical properties of the coating seems to be a problem. The work objective is to create a computational and analytical methodology for determining the thermal conductivity of coatings. This approach is based on experimental data and takes into account structural parameters of the material.Materials and Methods. The experiments were carried out with the blades of a high-speed gas turbine of a locomotive engine made of heat-resistant chromium-nickel alloy Inconel 713LC. An experimental multiphase coating of the Nb-Ti-Al intermetallic system with a thickness of about 80 microns was applied using vacuum ion-plasma technology. The two-beam scanning electron microscope Zeiss CrossBeam 340 was used in the work. The thermal conductivity of the coatings was determined by an experimental technique based on the measurement of the contact potential difference (CPD). Numerical values of this difference were obtained using a mirror galvanometer with high voltage sensitivity. A special signal amplifier and a USB oscilloscope were used to record the readings.Results. The calculation apparatus of the thermal conductivity determination technique is based on the experimental values of ∆φ CPD:– for the base metal (Inconel 713LC) +846 mkV;– for the coating Nb-Ti-Al – 90 mkV.The solution to the problem of the distribution of particles in a force field with a potential difference ∆φ is described by the Boltzmann distribution. Starting from the obtained result, we get:– CPD at the boundary of the contacting metals;– energy and thermal conductivity of the Fermi level;– electron relaxation time.The multidirectional influence that the dimensional differences of the particles of the second phase have on the effective thermal conductivity is considered. For this case, a dimensionless value of the effective thermal conductivity in the direction of each axis and the effective thermal conductivity of the composite are found. Porosity is taken into account according to the Maxwell – Aiken dependence and introduced into the general calculation system. The thermal conductivity of Nb-Ti-Al is established: λNbTiAl = 4,76 W/m.K. Thus, the thermal barrier coating Nb-Ti-Al fully meets its functional purpose.Discussion and Conclusion. The method of determining thermal conductivity described in the article is applicable only to conductive consolidated materials or composites with a continuous conductive matrix. The presented work completes the initial stage of creating a computational and analytical model for predicting the thermal conductivity of materials and coatings. The results of testing the model for materials with a complex structure showed its satisfactory accuracy. This indicates the expediency of using the two considered elements of the model. The first one is the instrumental measurement of the CPD. The second one is taking into account the features of the structural and phase state of the material. With the development of the model, it is expected to overcome its weaknesses:– the impossibility of using non-conductive objects to determine the thermal conductivity;– a significant decrease in the accuracy of determining thermal conductivity for materials and coatings with a gradient structure.

Investigation on the effect of nickel and nickel-chromium alloy pulse current plating on copper substrate

ABSTRACT In the present study, nanocrystalline nickel (Ni) and nickel-chromium (Ni-Cr) alloy coatings were developed on copper (Cu) substrate using pulse current. The pulse current parameters include a cycle time of 240 milliseconds at a duty cycle of 0.5 and 4.17 Hz frequency. The surface morphology, texture, hardness, scratch resistance and porosity were investigated for different coatings developed by pulse plating. Energy Dispersive Spectroscopy (EDS) analysis revealed good quality Ni and Ni-Cr alloy coatings developed on the copper substrate. The peak current of the pulse has been observed to have an impact on the coating weight and thickness. The micrographs of the coatings explored under Field Emission Scanning Electron Microscopy (FESEM), depict uniform coatings consisting of fine primary and coarse secondary granules of Ni and Cr. The hard primary and secondary Ni granules deposited on the surface of Cu increase its hardness, corrosion and wear resistance. Further, it was observed that the Ni-Cr alloy plated samples are harder and less porous in nature compared to Ni plated samples.

Effect of Passive Oxide Film Structure and Surface Temperature on the Rate of Anodic Dissolution of Chromium-Nickel and Titanium Alloys in Electrolytes for Electrochemical Machining: Part 2. Anodic Dissolution of Titanium Alloys in Nitrate and Chloride Solutions

Effect of Passive Oxide Film Structure and Surface Temperature on the Rate of Anodic Dissolution of Chromium-Nickel and Titanium Alloys in Electrolytes for Electrochemical Machining: Part 2. Anodic Dissolution of Titanium Alloys in Nitrate and Chloride Solutions

Study of the Influence of Silicon-Containing Diamond-like Carbon Coatings on the Wear Resistance of SiAlON Tool Ceramics

DLC coatings have low adhesive bond strength with the substrate and a high level of residual stresses. This paper is devoted to researching a complex of characteristics of a DLC-Si coating deposited on samples of SiAlON ceramics with intermediate coatings (CrAlSi)N pre-formed to improve the adhesive bond strength employing vacuum-plasma spraying. DLC-Si coatings were formed by chemical vapor deposition in a gas mixture of acetylene, argon, and tetramethylsilane supplied through a multichannel gas purge system controlling the tetramethylsilane volume by 1, 4, 7, and 10%. The SiAlON samples with deposited (CrAlSi)N/DLC-Si coatings with different silicon content in the DLC layer were subjected to XPS and EDX analyses. Tribological tests were carried out under conditions of high-temperature heating at 800C. The nanohardness and elasticity modulus of the rational (CrAlSi)N/DLC-Si coating with Si-content of 4.1% wt. were 26 ± 1.5 GPa and 238 ± 6 GPa, correspondingly. The rational composition of (CrAlSi)N/DLC-Si coating was deposited on cutters made of SiAlON ceramics and tested in high-speed machining of aircraft nickel-chromium alloy compared to uncoated and DLC-coated samples. The average operating time (wear resistance) of (CrAlSi)N/DLC-Si(4.1% wt.)-coated end mills before reaching the accepted failure criterion was 15.5 min when it was 10.5 min for the original cutters.

On the high-temperature oxidation behavior of a niobium-bearing high nickel-chromium alloy: microstructural evolution and implications on oxidation mechanisms

The oxidation behavior of a niobium-bearing high nickel-chromium alloy, widely used in the petrochemical industry, is systematically studied at 800 °C using a combination of transmission electron microscopy and atom-probe tomography experimental techniques and thermodynamic calculations. Oxidation leads to complex surface microstructures consisting of a protective chromia layer, an amorphous SiO2 (silica) layer, Fe- and Ni-rich metallic mushroom-like austenitic protrusions/precipitates, and sub-oxide voids with highly faceted surfaces. The thermodynamic equilibrium oxides of this alloy are studied as a function of oxygen activity using Thermo-Calc and compared to the observed microstructures. The growth kinetics of oxide layers are studied in detail.

Acoustic and Electromagnetic Properties of Maraging Iron–Chromium–Nickel Alloy with Addition of Copper in Mechanical Tension

Acoustic and Electromagnetic Properties of Maraging Iron–Chromium–Nickel Alloy with Addition of Copper in Mechanical Tension

On the mechanism of chromium-nickel two-phase alloy strengthening and fracture

The mechanism of strengthening of a two-phase chromium-nickel alloy 65Cr-(31-35)Ni–Ti–V–W depends on the heat treatment mode: the lattice periods of the α-phase (alloy matrix is a solid solution of Ni in Cr) in the hardened and equilibrium conditions are almost the same; level of strength and ductility properties of alloy determines dispersion and amount of γ-soft nuclei released during heat treatment (solid solution of Cr in Ni), its hardness is less than that of α-phase. Quenching from single-phase area from 1250°C and tempering at 800−900°C provides a higher strength than annealed alloy and increases the start temperature of high temperature failure. The nature of the destruction depends on the temperature. The influence of γ-phase is manifested more significantly at temperatures below equicohesive.