Measuring Ferromagnetic Phase Content Based on Magnetic Properties in Two-Phase Chromium–Nickel Steels

Russian Journal of Nondestructive Testing - The magnetic properties of samples prepared from two-phase austenitic–ferritic and austenitic–martensitic chromium–nickel steels of...     

Dry-Sliding Tribological Properties of Bronze–Graphite Composites

Bronze-uncoated and nickel-coated graphite composites were fabricated by powder metallurgy route. The tribological behaviors of composites sliding against AISI52100 steel ball under dry sliding condition were studied using a ball-on-disk tribometer. The nickel-coated graphite composites showed much better tribological properties in comparison with bronze and uncoated graphite composite. The friction coefficient of nickel-coated graphite composites decreased with increasing nickel-coated graphite content. However, the specific wear rate increased with the increase in nickel-coated graphite. The composite containing 15?wt% nickel-coated graphite showed the best self-lubricating properties because the compacted and stable mechanical mixed layer was formed on the worn surfaces. The wear mechanism of bronze 663 is adhesive wear and abrasive wear. The uncoated nickel-coated graphite composite shows the adhesive wear and delamination characteristics. However, the wear mechanism of nickel-coated composites is mildly abrasive wear.     

Assessing the Tribocorrosion Performance of Nickel–Aluminum Bronze in Different Aqueous Environments

Metallic components are frequently subjected to corrosion and tribological impacts during their service period, which results in accelerated material deterioration. In this work, a systematic investigation has been conducted to study the tribocorrosion performance of nickel–aluminum bronze (NAB) in different aqueous environments, using a pin-on-disc tribometer integrated with an electrochemical workstation. Results show that the aqueous environments considerably influence the friction and wear behavior of NAB. The friction coefficient and wear rate are highest in deionized water due to its poor lubricity. When an Al₂O₃ pin slid against NAB in 3.5% NaCl solution and seawater, a positive synergistic effect between wear and corrosion occurred. In addition, the relative contribution of corrosion–wear synergism to the total mass loss is greater in 3.5% NaCl solution than in seawater. Also of note is that applied potential plays a significant role in determining the material degradation.     

Production of Nickel–Chromium Coatings from Powder by Laser Cladding

Russian Engineering Research - The use of self-fluxing Ni12CrFe and NiCr16SiB3 powder in laser cladding within a protective atmosphere (argon) is considered. The characteristics of the powder are...     

The influence of the valena metal-plating additive on tribotechnical characteristics of the Steel–Bronze tribological system

The paper considers a change in the coefficient of friction and the temperature distribution in the contact zone of the steel–bronze tribosystem. Investigations were carried out by the shaft–bushing system for three values of the load in the mixed-to-boundary lubrication regime with SAE 80W transmission oil without and with Valena additive. It is found that the additive presence in oil decreases the coefficient of friction by 11–21%, depending on the applied load. At the same time, the maximum decrease in the coefficient of friction is observed at a maximum applied load of 1500 N.     

Influence of the Mechanical Seals on the Dynamic Performance of Rotor–Bearing Systems

In this paper, to consider the effects of mechanical seals, a lumped-mass model and the transfer matrix method are used to establish the equations for the dynamics performance of rotor bearing system. The general inverted iteration method is also used to solve the eigenvalue problem of these equations. To check the response of the rotor bearing system under unbalance motivation, the Gauss method is used to calculate the dynamic response of the constrained vibration. The results, based on the dynamic properties calculation of a typical mechanical spiral seal, such as stiffness coefficients and damping coefficients, exert the influence of the mechanical seal on the rotor bearing system of the high-speed machinery. Meanwhile, some structure parameters that may affect the dynamic performance and forced vibration under unbalance motivation of the rotor bearing system considering mechanical seals are analyzed in the paper. The analysis results show that the mechanical seal more or less has effects on the rotor bearing system. The mechanical seal has much more effects on the flexible rotor bearing system than on the rigid one. For instance, in a certain case, if the effects of the mechanical seal were taken into account, the system s critical speed may increase by 70 80%.     

Influence of Parameters of Reactive Magnetron Sputtering on Tribomechanical Properties of Protective Nanostructured Ti–Al–N Coatings

The influence of substrate temperature and bias voltage on the structure and tribomechanical properties of the Ti–Al–N coatings obtained by reactive magnetron sputtering technique has been investigated. The structure and elemental and phase compositions have been studied by scanning electron microscopy, Rutherford backscattering, and X-Ray diffraction. The results of friction and wear experiments indicated that the lowest coefficient of friction (three times lower than 12Cr18Ni10Ti) corresponded to a coating deposited at a bias voltage of–200 V and a substrate temperature of 340°С, while the most wear-resistant coating (under a load of 700 mN and the testing time of 1080 s) was Ti–Al–N sputtered at a bias voltage of–200 V and a substrate temperature of 440°С.     

Eddy-Current Evaluation of Wear Resistance of Case-Hardened Chromium–Nickel 20KhN3A Steel

The paper considers feasibility of eddy-current evaluation of the wear resistance of the quenched and tempered (100–400°C) case-hardened 20KhN3A steel under conditions of abrasive wear and sliding friction. The effect of cold processing on the susceptibility of the eddy-current method to the wear resistance of a hardened layer has been studied. The effect of the carbon content in the martensite prior to tempering over the range of 0.3 to 0.9 mass % on eddy-current measurements is discussed.     

Mechanical Characteristics and Adhesive Strength of Nickel–Chromium Coatings Applied by Laser Cladding

Russian Engineering Research - The mechanical characteristics and adhesive strength of nickel–chromium coatings produced by the laser fusion of Ni12CrFe and PR-NiCr16SiB3 powder are compared...     

Effects of Silicon Content on the Mechanical Properties and Lubricated Wear Behaviour of Al–40Zn–3Cu–(0–5)Si Alloys

In this work, one ternary Al–40Zn–3Cu and seven quaternary Al–40Zn–3Cu–(0.25–5)Si alloys were synthesized by permanent mould casting. Their microstructure, mechanical and lubricated wear properties were investigated using appropriate test apparatus and techniques. As the silicon content increased the hardness of the alloys increased, but their elongation to fracture decreased. Tensile strength of the alloys decreased with increasing silicon content following a sharp decrease and a slight increase. Among the silicon-containing quaternary alloys the highest and the lowest tensile strength values (348 and 305 MPa) were obtained with the Al–40Zn–3Cu–2Si and Al–40Zn–3Cu–5Si alloys, respectively, while the base alloy (Al–40Zn–3Cu) exhibited a tensile strength of 390 MPa. However, the volume loss due to wear of the alloys increased with increasing silicon content after showing an initial increase and a sharp decrease. The lowest wear loss was obtained with the alloy containing approximately 2% Si which has the highest tensile strength among the quaternary alloys containing more than 0.25% Si. Wear surfaces of the alloys were characterized mainly by smearing indicating that adhesion is the dominant wear mechanism for the experimental alloys.     

Revealing Magnetic Anisotropy in Austenitic Chromium–Nickel Steel After Rolling

Russian Journal of Nondestructive Testing - We study textures, phase composition, and magnetic anisotropy in austenitic samples deformed by rolling of 09Kh17N5Yu steel with the formation of...     

Effect of Micro-scale Y Addition on the Fracture Properties of Al–Cu–Mn Alloy

Rare earth (RE) elements have positive effects on Al alloy, while most research is focused on microstructure and mechanical properties. As important application indices, toughness and plasticity are properties that are sensitive to alloy fracture characteristics, and few research studies have characterized the fracture properties of Al–Cu–Mn alloy on RE elements. The effect of different contents of Y on the fracture properties of Al–Cu–Mn alloy is investigated. T6 heat treatment (solid solution and artificial aging treatment), optical microscope (OM), scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) methods are applied to the alloy. Results showed that when Y element is present at 0.1%, the section of the as-cast alloy has smaller sized dimples and the fracture mode presents ductile features. Slight changes in hardness are also observed and maintained at about 60 HV. With increasing content of the RE element Y from 0.1 to 0.5%, the θ phase and Cu atoms in the matrix were reduced and most stopped at Grain boundaries (GBs). Micro-segregation and an enriched zone of Y near the GBs gradually increased. At the same time, the inter-metallic compound AlCuY is aggregated at grain junctions causing deterioration of the micro-structure and fracture properties of the alloy. After T6 treatment, the flatness of the fracture surface was lower than that of all the as-cast alloy showing lots of dimples and teared edges with a significant increase in hardness. When Y content was 0.1%, the strength and hardness of the alloy increased due to refinement of the grain strengthening effect. The content of Y elements segregated in the inter-dendritic zone and GBs is reduced. Plasticity and deformation compatibility also improved, making cracks difficult to form and merge with each other along adjacent grain junctions and providing an increased potential for ductile fracture. This paper proposes the addition of RE Y as an effective and prospective strategy to improve the fracture properties of the Al–Cu–Mn alloy and provide a meaningful reference in terms of improving overall performance.     

Chromium and Detonation Nanodiamond Based Coatings of the Chromium–Carbon System: Deposition by Magnetron Sputtering,Peculiarities of Phase Composition,and Tribological Properties

The structure, the chemical and phase compositions, and the micromechanical and tribological properties of chromium–carbon coatings obtained by the magnetron sputtering of composite and/or sintered chromium–nanodiamond targets are investigated. The coatings possess the composite multiphase structure composed of chromium and its phases formed as a result of the chemical interactions of the target material’s components both between each other and with the reactive gas if present in a sputtering atmosphere. Several technological factors influencing the structural and phase peculiarities of the coatings, their nanohardness, and the dry friction behavior at high contact pressures are studied.     

Influence of the microstructure of Al–Si alloy on the surface-layer quality in microarc oxidation

The properties of the hardened surface layers formed by microarc oxidation on Al–Si alloy billet are investigated. The microhardness, thickness, and porosity of the surfaces formed depend on the alloy structure.     

Influence of High-Pressure Coolant Assistance on the Machinability of the Titanium Alloy Ti555–3

The origin of this article is the quantification of productivity gains and the improvement in surface integrity seen for a recent titanium alloy that is seeing increasing use in the aeronautical industry. The Ti555–3 titanium alloy, which is starting to find greater application in the aeronautical field, exhibits certain difficulties in terms of machining. High Pressure Coolant (HPC) assisted turning consists of projecting a high pressure coolant jet between the chip and the tool. Comparisons are made between assisted turning using variable jet pressure and conventional turning (dry and classical lubrication). It is shown that it is possible to improve productivity by using HPC-assisted machining. The results highlight good chip fragmentation and a great improvement of tool life with HPC assistance. Surface integrity is also shown to be improved, through surface roughness parameters that decrease, and surface residual stresses that become more compressive. These effects have been attributed to the thermo-mechanical action of the coolant jet resulting in lower cutting forces, lower coefficient of friction and lower temperature in the cutting zone.     

Influence of Input Acceleration of Broad-Band Random Vibrations on the Amplitude–Frequency Characteristics of Hydraulic Bearings

Russian Engineering Research - The amplitude–frequency characteristics of hydraulic bearings under the action of broad-band random vibrations with different input root-mean-square...     

Influence of the electromagnetic gap in gas–magnetic bearings on the output characteristics of high-speed rotor systems

The electromagnetic gap in gas–magnetic bearings has a considerable influence on the output load and rigidity characteristics of high-speed rotor systems, as shown by experiments and simulation.     

Influence of the Addition of Vanadium Nitride on the Structure and Specifications of a Diamond–(Fe–Cu–Ni–Sn) Composite System

This article discusses the influence of the addition of vanadium nitride on the mechanical and operational properties of diamond composite material based on metallic bond comprised of iron, copper, nickel, and tin obtained by sintering in a mold at 800°C for 1 h with subsequent hot repressing. It has been established that the addition of vanadium nitride in the amount of 2 wt % to diamond–(51Fe–32Cu–9Ni–8Sn) increases the ultimate compressive strength from 846 to 1640 MPa and bending strength from 680 to 1120 MPa, as well as decreases the wear intensity of the composite material from 0.0069 to 0.0033 g/km. The mechanism of improving the tribological properties has been revealed.     

Influence of microstructure and texture on the corrosion and tribocorrosion behavior of Ti–6Al–4V

In this paper, the corrosion and tribocorrosion behaviors of Ti–6Al–4V alloy having different phase composition, texture and microstructure was investigated. Potentiodynamic polarization and electrochemical impedance spectroscopy measurements were performed to evaluate the corrosion behavior. Sliding wear tests under anodic and cathodic polarization conditions were made to assess the tribocorrosion properties. SEM, OM, and XRD were used to characterize the microstructure, texture, and morphology of the samples. The corrosion resistance was found to depend on to the microstructure, as well as the texture of the surface. A bi-modal microstructure and prismatic texture showed the best corrosion behavior. However, when corrosion was coupled to sliding wear (tribocorrosion), the hardness was found to be the controlling factor.     

Investigation of the Internal Amplification Effect on Planar (p +–n–n +) Structures Made of High-Resistivity Silicon

The first results of studies of special strip and pixel silicon detectors are presented. The detector structures allow the creation of high electrical fields (5 × 10⁵ V/cm) near p–n junctions that are powerful enough to initiate an avalanche multiplication of charge carriers. The possibility of internal amplification in a semiconductor detector similar to the proportional amplification in gas counters is shown. The spectrum of particles from ²³⁸Pu (E = 5.5 MeV) demonstrates an amplified peak at an energy of 70.2 MeV and an energy resolution FWHM = 10.2 MeV.