No 1(117) (2024)

The temperature of the end of finishing stage, cooling rate and coil winding temperature are structure-sensitive parameters for bainite-grade steels in the production of plate less than 10 mm thick. Simulation modeling of high-speed thermo-deformation processing of Cr–Ni–Mo bainitic steel samples has been carried out in order to select the most rational technological modes in continuous hot rolling mills. The influence of strain rate and temperature as well as niobium and vanadium microalloying additives on phase transformations has been investigated.

Textures of medium carbon steel, hot rolled and then quenched, have been determined by Electron backscatter diffraction (EBSD). To ensure representativeness of results, a rather large treated scan covered about a thousand of prior grains, each containing several thousands of measurement points. Considering inter-phase orientation relationships peculiar to martensitic steels, textures of the high temperature phase (austenite) have been assessed in terms of the transformation textures. Thus, deformed and recrystallized states of austenite dependent on the rolling conditions can be distinguished. To verify EBSD data, martensite textures were measured by an independent method of EBSD whereas morphology of the prior grains was revealed by means of chemical etching.

Billets for drawing of microwires based on Grade 4 titanium and protective sheath of M1 copper have been obtained at different temperatures by hot pressing method with drawing coefficient µ = 16. The influence of the billet heating temperature on the pressing pressure, configuration of the interface of bimetal materials and thickness of the intermetallide layer is shown. The influence of elastic compression pressure of composite copper-titanium billets in the range of 350–1400 MPa on the formation of intermetallide at the interface of materials at 850°C has been analyzed.

With the furnace surfacing method, a composite alloy is obtained, consisting of reinforcing particles of tungsten and cupronickel carbides, which, after exposure to the melting temperature of the binder alloy, form a wear-resistant layer on the surface being hardened. It has been established that in the zone of connection of the composite alloy relit – cupronickel with the steel surface of the part, in the absence of conditions that guarantee auto-vacuum cleaning of the surface from oxides, an interlayer with an imperfect crystal structure is formed, which leads to delamination of the deposited alloy. It has been experimentally shown that the use of additional control for the gas tightness of the surfacing space makes it possible to improve the quality of the deposited surface when furnace hardening of metallurgical equipment parts with the composite alloy relit – cupronickel.

The results of a study of the technological properties of titanium powders of pseudo-α and pseudo-β alloys are presented. A comparative analysis of the characteristics of powder materials obtained by centrifugal spraying has been carried out. The results of the granulometric composition of the powders were obtained, and the calculation of the spatial packing of particles was applied within the framework of the hard sphere model for various fractional compositions. To compare the microstructure and mechanical properties, test samples from pseudo-α and pseudo-β titanium alloys were obtained using the hot isostatic pressing method according to selected modes.

The results of the experimental study of powder materials of various brands and classes (stainless steel, precision soft and hard magnetic alloys) are presented, the influence of their parameters (particles, fracture, fluidity, bulk density) on the properties of finite additive samples is evaluated. The impact of melting parameters on the porosity of additive samples has been studied.

The paper shows the influence of various laser processing modes of cold spray Ni–Ti–WC coatings. It has been shown that the microhardness of the resulting coatings reaches 1200 HV. The formation of diamond-shaped, pore-free WC inclusions with a size of 500 nm has a positive effect on the microhardness. The article provides recommendations for the industrial production of Ni–Ti–WC system coatings.

—The effect of ultrasonic processing at resonant frequencies of 22 and 44 kHz of a monolayer formed by three-dimensional printing from prepregs reinforced with continuous carbon fiber on the resistance to the flow of solid particles by imitating it by jet-abrasive treatment is investigated.
The increment of the weight of both control and experimental samples in comparison with the initial state was established. It is shown that the force effect of ultrasound in rational modes contributes to a decrease in weight gain by 31.4% when processed at a frequency of 22 kHz and by 9% when processed at a frequency of 44 kHz. The decrease in weight increment is determined by an increase in the density of the monolayer structure after ultrasonic exposure, which leads to an increase in surface hardness in units of Schor-D by 13.5% at a frequency of 22 kHz and by 10% at a frequency of 44 kHz.

Further development of local approach models is considered from viewpoint of links of local brittle fracture properties with embrittlement mechanisms and fracture modes for RPV steels. Strategy and program of experimental and numerical investigations have been developed that allows one to find how various embrittlement mechanisms and fracture modes are connected with the conditions of nucleation and propagation of microcracks resulting in brittle fracture of RPV steels. 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) initial (as-produced); (2) thermally embrittled by a hardening mechanism; (3) thermally embrittled by a non-hardening mechanism; 4) irradiated. Experimental studies include testing specimens of different geometry (smooth and notched round bars, and cracked compact tension specimens), which allows us to obtain characteristics of brittle fracture under various stress triaxialities. Numerical studies performed with the probabilistic brittle fracture model Prometey aim to obtain the brittle fracture properties on micro- and macroscales for all the investigated states of the materials.
Part 1 of the paper presents information concerning the investigated materials, the used procedures and methods. Part 2 gives the test results of smooth round bars of the investigated materials in various states and the stress-strain curves determined over wide temperature range. The experimental results for various specimens from the investigated steels in various states are represented and compared with the results predicted with the Prometey model in Part 3.

Instrumental measurements of microhardness were carried out using a Vickers indenter at a constant strain rate. The yield strength values were determined for austenitic chromium-nickel steels 08Kh18N10Т, 10Kh18N9 and 08Kh16N20M2Т in the initial (non-irradiated) state, after neutron irradiation at various regimes, as well as after plastic prestrain. Similar measurements were carried out for chromium stainless steels of the ferritic-martensitic class 07Kh12NMFB and 16Kh12MVSFBR (EP-823) in the initial (non-irradiated) state and after heat treatment, leading to hardening of the material and also after neutron irradiation. The relationships between microhardness and yield strength were determined for all studied states of all steels studied. A unified correlation has been established between hardening in terms of the yield strength and hardening in terms of Vickers micro-hardness, independently of the nature of the strengthening factor and the class of steel.