The paper presents the results of long-term high-temperature creep tests of Russian reactor steels with ferriticmartensitic structure (the duration of some measurements exceeded 8 years). In the current study, the structural-phase transformations, characteristics of creep and long-term strength at 650 degrees C, 670 degrees C, and 700 degrees C under 60-140 MPa in oxide-free and oxide containing steels were determined. The creep tests were performed on specially designed transverse micro-specimens prepared from fuel elements cladding used in the fast-neutron reactor. The creep velocity of the ferritic-martensitic reactor steels was established to be specified by resistance of lath martensite and ferrite structures to diffusion processes of return and recrystallization. The most heat-resistant oxide-free steel contains the largest amount of refractory elements and carbides. The best heat resistance was observed for the steel hardened with thermal-resistant yttrium-titanium nanooxides. The samples made of this steel demonstrated one order less creep velocity at 700 degrees C under 100 MPa and 100-fold time to fracture in comparison with the oxide-free reactor steels.

This paper discusses a comparative micromechanical and tribological analysis of laser-cladded equiatomic FeNiCr coatings reinforced with TiC and NbC particles. Two types of coatings, FeNiCr-TiC (3 wt.% TiC) and FeNiCr-NbC (3 wt.% NbC), were deposited onto an AISI 1040 steel substrate by means of short-pulsed laser cladding. The chemical composition, microstructure, and micromechanical and tribological characteristics of the coatings were systematically investigated via optical and scanning electron microscopy, Raman spectroscopy, and mechanical and tribological tests. The average thicknesses and compositional transition zones of the coatings were 600 ± 20 μm and 150 ± 20 μm, respectively. Raman spectroscopy revealed that both coatings are primarily composed of a single FCC γ-phase (γ-FeNiCr). The FeNiCr + 3 wt.% TiC coating exhibited an additional TiC phase dispersed within the γ-FeNiCr matrix. In contrast, the FeNiCr + 3 wt.% NbC coating displayed a more homogeneous distribution of finely dispersed NbC phase throughout the composite, leading to enhanced mechanical behavior. Micromechanical characterization showed that the FeNiCr + 3 wt.% NbC coating possessed higher average microhardness (3.8 GPa) and elastic modulus (180 GPa) compared to the FeNiCr + 3 wt.% TiC coating, which had values of ~3.2 GPa and ~156 GPa, respectively. Both coatings significantly exceeded the AISI 1040 steel substrate in tribological performance. The FeNiCr + 3 wt.% TiC and FeNiCr + 3 wt.% NbC coatings exhibited substantial reductions in both weight loss (37% and 41%, respectively) and wear rate (33% and 42%, respectively) compared to the substrate material. These findings indicate that more finely dispersed NbC particles are better suited for hardening laser-cladded equiatomic FeNiCr-NbC coatings, making them advanced candidates for industrial applications.

Laser cladding of the equiatomic medium-entropy alloy (MEA) FeNiCr-B4C coatings on AISI 1040 steel substrate was carried out by pulsed laser deposition. X-Ray diffraction analysis showed that the formed coatings consist of a single face-centered cubic (FCC) γ-phase, space group Fm-3m, independently of the B4C content. However, additional TEM analysis of the FeNiCr coating with 3 wt.% B4C showed that it is characterized by two-phase FCC structure consisting of the grains up to 1 µm in size and banded interlayers between the grains. The grains are clean; the density of dislocations inside the grains is low. Based on the SEM analysis of the microstructure, it was found that the cross-sections of all obtained specimens are characterized by average coating thickness of 400 ± 20 μm, sufficiently narrow (100 ± 20 μm) “coating-substrate” transition zone and the presence of a small number of defects: cracks and pores. The characterization of the mechanical properties showed that in-situ alloying with 1 and 3 wt.% B4C is resulted in noticeable increase in microhardness, i.e. 16 and 38%, with a slight decrease in ductility, i.e. 4 and 10%, compared to the B4C-free FeNiCr coating. Thus, in-situ alloying with B4C can be considered as a promising method for hardening of laser deposited MEA FeNiCr coatings.

A mixture of the Al 2 Au intermetallic compound and copper powders was compacted and then melted in an argon atmosphere to form an Al 2 Au + Cu ingot. Study of the structure of the alloy showed the formation of areas of the Al 2 Au intermetallic phase, which are brightly colored and are present in the AlAu intermetallic matrix. Thin Cu-enriched streaks occur inside the AlAu matrix. The optical characteristics of the prepared ternary compound have been measured. The microindentation of the intermetallic phases has been performed; the microhardness and contact elastic modulus have been determined.

Many machinery parts operating in contact with rapidly flowing fluid flows (for instance, turbine blades of hydroelectric power plants, valves, pump impeller blades, ship propellers, cooling systems of various assemblies, and so on) are exposed to wear such as cavitation erosion. The elimination or reduction of cavitation erosion is an urgent task, because it makes it possible to achieve significant cost efficiency. This work describes a procedure that has been developed and patented for estimating resistance against the cavitation erosion of cermet thermal sprayed coatings (WC–10Co4Cr and WC–20CrC–7Ni). The cermet coatings were produced by high velocity air fuel (HVAF) spraying. The aim of this work is to test the new estimation procedure of coating resistance against cavitation impact, which differs from the standard procedure by position of tested specimen with regard to fluid used for testing. In addition, the structure of the coatings has been analyzed in the initial state before tests and their behavior after cavitation impact has been studied using scanning electron microscopy. The coating resistance has been estimated by the criterion of material volume loss. The experimental results have demonstrated that the cavitation resistance of the WC–20CrC–7Ni coating is somewhat higher in comparison with WC–10Co4Cr, despite its lower average hardness (850 ± 90 HV 0.5 against 950 ± 60 HV 0.5 ). An analysis of surface and transversal cross sections of the coatings demonstrates that they are characterized by different mechanisms of erosion destruction. It can be concluded that the existence of defects (pores) in the coating structure is the main reason promoting a decrease in their resistance against cavitation erosion. Therefore, this procedure has proven its efficiency upon obtaining experimental data for an analysis of the cavitation wear of cermet thermal sprayed coatings.

A mixture of fine powder of the Al2Au intermetallic compound and coarse Cu-powder was processed by the ball milling (BM) technique. The phase composition of the obtained powder product and the microstructure of separate particles were studied by TEM, SEM and XRD methods. It was found that BM for 4 h leads to the formation of Cu-clusters that are evenly distributed among the Al2Au-particles. There was discovered a decrease in the lattice parameter of the Al2Au-phase, which is associated with the formation of a solid solution of copper in Al2Au. The crystallite size in the resulting powder is near 20 nm. The mechanical properties of the (Al2Au + Cu)-powder were evaluated using nanoindentation tests. (c) 2021 Elsevier B.V. All rights reserved.

Many machinery parts working in contact with a fast-flowing fluid flow (e.g. turbine blades of hydroelectric power plants, valves, pump impeller blades, ship propellers, cooling systems for various units, etc.) are subjected to such type of wear as cavitation erosion. An important objective is to eliminate or reduce cavitation erosion so as to achieve a considerable economic effect. This research uses a patented technique developed to evaluate the cavitation erosion resistance of cermet thermal spray coatings (WC–10Co4Cr and WC–20CrC–7Ni). These coatings were prepared using high velocity air fuel thermal spraying (HVAF). The aim of this study is to test a new technique for evaluating coating cavitation resistance, which differs from the standard one by specimen positioning relative to the testing liquid. In addition, scanning electron microscopy (SEM) was used to analyze the initial structure of the coatings prepared and study their behavior after cavitation exposure. The material volume loss criterion during the cavitation test was used to evaluate the coating resistance. The results of cavitation tests showed that the WC–20CrC–7Ni coating has a somewhat higher cavitation resistance than that of WC–10Co4Cr despite its slightly lower average hardness (850±90 HV0.5 versus 950±60 HV0.5). The study of coating surfaces and cross-sections showed that they feature by different erosion mechanisms. It can be concluded that the presence of defects (pores) in the coating structure is the main reason for reducing their cavitation erosion resistance. Therefore, the developed technique proved effective in obtaining experimental data to analyze cermet thermal spray coatings for cavitation wear.

Conditions for the formation of microconcentration inhomogeneities in Fe–Ni alloys, which can decrease their invar characteristics, are determined. The nickel separation can be reached in the course of short-term annealing as a result of deformation-induced nickel segregation, nickel redistribution between martensite and austenite and between ferrite and austenite as well.

A narrow temperature range of changes in the mechanism and kinetics of structural-phase transformations during mechanical alloying under deformation in rotating Bridgman anvils was determined by the methods of Mössbauer spectroscopy, electron microscopy, and mechanical tests in the high-nitrogen chromium-manganese steel FeMn22Cr18N0.83. The experimentally established temperature region is characterized by a change in the direction of nitrogen redistribution-from an increase in the N content in the metal matrix during cold deformation to a decrease with an increase in the temperature and degree of severe plastic deformation. The change in the direction of nitrogen redistribution is due to the acceleration of the decomposition of a nitrogen-supersaturated solid solution of austenite with the formation of secondary nanocrystalline nitrides. The presence of a transition region for the mechanism of structural-phase transitions is manifested in the abnormal behavior of the mechanical properties of steel.

There were investigated tribological properties of CrAlSiC coatings deposited by two techniques. In both techniques a plasma source of a cathode-arc discharge with Cr-Al-Si composite target served the source of Cr, Al, and Si atoms during coating deposition. A plasma source of a pulsed cathode-arc discharge with graphite cathode and a gas discharge device to generate a non-self-sustained discharge in argon-acetylene mixture have been used for generating carbon plasma in first and second techniques, correspondingly. First coating has a low coefficient of friction. Under frictional action, coating wears out uniformity without chipping. Second coating is less resistant to frictional action.

The structure and the mechanical and electrical properties of composites with 7 and 49 magnesium fibers in the copper matrix are studied in this work. It was found that the strength of a deformed composite wire with the maximum volume fraction of Cu/Mg interfaces exceeds the theoretical estimate and the strength of pure copper. It is shown that deformation-induced formation of high-strength solid solutions of magnesium in copper at the interfaces of the composites occurs during the manufacturing process. The low electrical resistivity of the composites is provided by a copper shell.

The authors present the results of an investigation in Fe-Ni-Cr austenitic alloys of the low-temperature deformation-induced segregations of nickel that form in the micro regions being (i) located close to grain- and subgrain boundaries and (ii) characteristic of the concentration and magnetic inhomogeneities indicated by the appearance of a dark diffraction contrast at the electron diffraction patterns taken from these regions typical (at the same time) of an enhanced value of Curie temperature. The observed effects were connected with the micro distortions caused by the local change of lattice parameter because of an increase in nickel concentration, as well as in the result of a magnetostriction dilatation. Using methods of the X-ray energy dispersive spectroscopy (XEDS) and atomic-probe body-section radiography (tomography - APT) has made it possible to determine the borders of those regions of austenite that were characteristic of an enhanced concentration of nickel in the fields of the localisation of a deformation-induced segregation of nickel in the vicinity of grain (subgrain) boundaries of austenitic alloys of the types Fe-13Cr-30Ni and Fe-37Ni-3Ti.

The design and characteristics of the displacement sensor based on a hysteresis- and friction-free Hall-effect transducer are described. The conversion factor is 40 mV/mm at a supply current of 90 mA. The displacement ranges are within the margins of ±1 mm and ±0.4 mm with a deviation from the linearity of less than 1%. The stiffness is 10 g-force/mm and the achieved resolution is 1.25 nm.

Nickel redistribution and austenite decomposition into ferrite with the formation of up to 15% α‑ferrite crystals 10–100 nm in size in a fairly stable Fe–36Ni–3Cr invar alloy were found. The austenite decomposition during heating in a 250–400°C temperature range is intensified by preliminary strong plastic deformation by rolling or shearing under high pressure.

The method of visually identifying microregions with increased nickel concentration in austenitic Fe–Ni alloys by the appearance of dark diffraction contrast in electron-microscopic images has been laid a foundation for. The appearance of such a contrast can be explained by the microdistortions arising as a result of local changes of the lattice parameter due to the changes in the composition, and also as a result of magnetostriction dilatation in these regions with increased Curie temperature.