Problems of materials science

To assess a state of parent austenite before the steel quenching, a scalar textural index for martensite and bainite is introduced in terms of EBSD orientation data. Deformed and recrystallized states of the parent phase are discriminated by the sign of this index, whereas its magnitude in each of the two reflects the texture sharpness depending on the hot rolling mode. Accordingly, in a virtual case of randomly distributed orientations the considered parameter vanishes. Performance of the proposed approach is demonstrated on medium carbon martensitic steel hot rolled at laboratory conditions and on industrial rolled plates of low carbon bainitic steel.

In order to utilize municipal solid waste (MSW), a prototype reactor for thermal processing was created using materials developed at the National Research Center “Kurchatov Institute” – Central Research Institute of Structural materials “Prometey”, the technology for decomposing MSW in the reactor was developed, and its tests were carried out. The test results allowed us to conclude that the use of pyrolysis reactors for recycling ensures the environmental safety of the process and produces high-temperature gas (1000–1200°C) suitable for further use in power plants. Technical requirements were determined for the development of an industrial reactor for the disposal of solid waste with a productivity of up to 10 t/h, taking into account the shortcomings identified during testing of the prototype.

The paper presents results of the study of the structure and physico-mechanical properties of ceramics composits α-Al₂O₃ + n Y₂O₃ (n = 0; 0.5; 1; 1.5; 2; 3; 4; 5 wt.%) based on the basis of polymorphic modifications γ+θ-Al₂O₃ depending on the concentration of the Y₂O₃ doping impurity and the annealing temperature of the powder mixtures (800 and 900°C). The effect of mutual protection against crystallization was discovered, which results in mutual inhibition of crystallization processes in Al₂O₃–Y₂O₃ powder systems. By X-ray diffraction analysis, the formation of a phase of yttrium-aluminum garnet Y₃Al₅O₁₂ (YAG) in ceramics has been established. The dependence of the mechanical characteristics of the materials under study on the amount and size of the formed phase YAG has been revealed.

The paper studies the structure of nickel-diamond composite electrochemical coatings obtained from the suspension electrolyte with ASM 7/5 powder. When the content of diamond powder in the electrolyte is 10 g/l, coatings are deposited with a uniform distribution of the reinforcing phase and a diamond volume fraction of up to 20%. Studies of the structure of the nickel coating matrix have revealed that, in comparison with standard galvanic nickel, which has a pronounced texture, the composite coating matrix has a finely dispersed structure with random grain orientation. Comparative measurements of nanohardness made it possible to record the strengthening of composite coatings matrix compared to galvanic nickel. Along with the high hardness of the reinforcing component and the relatively large particle size, this determines the high microhardness of the composite coating, which averages 860 HV.

The results of a comprehensive study of the electrical strength of glass insulation and the electrical resistance of cast microwires insulated with borosilicate glass in the temperature range from −60 to 155°C are presented.

The physical-mechanical and tribological properties of anti-friction carbon fiber plastic UGET based on low-modulus carbon fabric “Ural T-15R” have been studied in order to increase the magnitude of the ultimate deformation and reduce the elastic modulus through the use of a modified thermosetting matrix ET-4 instead of the traditionally used ET-2.

Modes of polymerization and of heat treatment of epoxy binders were selected considering the results of the experiments. Prototypes of prepregs were obtained by solution impregnation on the UPST-1000M line and then processed into PCM by hot pressing. Laboratory samples were made and physical and mechanical tests were carried out to determine the ultimate strength under compression, shear and bending stress under destruction, as well as Charpy impact strength. Steel 20Kh13 and oxidized titanium alloy PT-3V were used as counter body rollers to determine carbon fiber tribosets.

It was shown that carbon fiber samples based on chemically modified binder ET-4 with two-stage polymerization and heat treatment mode in the range of 90°C to 180°C both have better physical-mechanical and tribotechnical properties, in contrast with the analogue with a three-stage mode and carbon fiber carbon heat at friction over 20Kh13 steel and oxidized titanium alloy PT-3V.

The results of the study of the influence of the thermophysical properties of the welding flux obtained by processing man-made waste of electric steelmaking (metallurgical slag) on the structure and properties of welded butt joints of thin-sheet low-carbon steel, with automatic arc welding on ceramic linings, are presented. Welding modes have been established using the developed flux, contributing to the achievement of seam sizes according to GOST8713–79, C4 joints, compliance with the mechanical properties of joints close to the base metal and ensuring a minimum level of welding deformations and stresses.

The cases in laboratory practice of experimental investigations of fracture toughness are considered, when as a result of the tests the determination characteristics of fracture toughness (K_JC, J_C, J_R-curves, δ_R-curves) cannot be performed correctly in accordance with the requirements of existing standards. A simplified technique for constructing J_R-curves has been developed, allowing in these cases to obtain the necessary characteristics of crack resistance (J_R-curves, J_1C, J_C, δ_R-curves) and thereby significantly increase the information content of the tests carried out. Methodological recommendations on conducting tests and processing of their results are given. Approbation and verification of the proposed method have been carried out.

Understanding of an accuracy related to the evaluation of special mechanical performances of materials is an essential part of the quality control system providing for safe operation of modern structures in severe climatic conditions in far locations where any emergency and repair activities are hindered. In absence of a priori known values of such performances the methodic basis of uncertainty calculation procedures should be developed. Relevance of the problem is supported by the requirement of Russian Accreditation Agency regarding the availability and due application of the corresponding methods in test laboratories as for directly measured parameters as for ones calculated from the test results. Uncertainty calculation procedures are suggested as a background for the developed specialized software.

Radiation and thermal embrittlement of RPV steels are studied from viewpoint of links of brittle fracture properties on micro- and macroscales. Brittle fracture properties on macroscale (such as fracture toughness and fracture stress) and the critical parameters controlling nucleation and propagation of microcracks are determined on the basis of the probabilistic brittle fracture model Prometey. The experimental and numerical investigations are performed for 2Cr–Ni–Mo-V steel and A533 steel used for RPVs of WWER and PWR types. RPV steels are studied in the following states: (1) the initial (as-produced) state; (2) the thermally-embrittled state modelling hardening mechanism of embrittlement; (3) the thermally-embrittled state modelling non-hardening mechanism of embrittlement; (4) the irradiated state. The test results of various specimens (smooth and notched round bars and cracked compact tension specimens) from the investigated steels in various states are represented over brittle fracture temperature range. Brittle fracture modelling is performed with the Prometey model for all the above specimens, and the experimental and numerical results are compared. On the basis of the obtained results the links between embrittlement mechanisms, fracture modes and microcrack nucleation and propagation properties are found.

A methodology for determining the irradiation mode for ferritic-martensitic steels at ion accelerator has been developed and experimentally substantiated, providing radiation hardening of these steels, identical to that realized under neutron irradiation. The change in Vickers microhardness is used as a measure of radiation hardening. The paper presents the results of a study of radiation-induced changes in the microhardness of austenitic steels 08Kh18Н10Т and 08Kh16Н20М2Т irradiated in reactors SM-3, VVER-440, BOR-60, SM-3 + BOR-60 to damaging doses of 10.2–33.7 dpa in the interval of temperatures 60–500°C. A study of radiation-induced changes in microhardness in a wider range of irradiation temperatures, post-irradiation annealing of irradiated steels was carried out in the range from 400 to 600°C, simulating irradiation at temperatures equal to annealing temperatures. Data are presented on radiation-induced changes in microhardness after irradiation in the ion accelerator of the State Scientific Center of the Russian Federation – Institute for Physics and Power Engineering named after A.I. Leypunsky (IPPE) with Ni⁺⁴ ions and He⁺ ions up to concentrations of 0–7 appm/dpa at damaging doses of 13–30 dpa and temperatures of 300–650°. A transition function has been established that connects the irradiation of temperatures during neutron and ion irradiation at a given damaging dose, ensuring the same radiation hardening of austenitic steels.