Ашық рұқсат
Рұқсат берілді
Тек жазылушылар үшін
№ 5 (2025)
Articles
STUDY OF THE INFLUENCE OF THERMAL EFFECT ON THE STRUCTURE OF THE AlNiCoFeCr AND AlNiCoFeCrCu HEAT ELECTRICITY PRODUCED BY ARC MELTING
Аннотация
The phase composition and morphological features of the structure of high-entropy AlNiCoFeCr and AlNiCoFeCrCu alloys of equiatomic compositions obtained by arc melting, as well as the evolution of their structure after thermal action (up to 1650 °C) were studied using high-resolution electron microscopy and X-ray diffraction. The structure of the AlNiCoFeCr alloy after arc melting is a solid solution formed by grains of the B2 phase - 120 nm in size. The microhardness of the alloy is ~ 5000 MPa. When the alloy is heated to 1650 °C and then solidified at a rate of 1 deg/s, a structure of grains of the B2 phase ~ 50 µm in size with subgrains ~ 0.5 µm in size is formed. Two phases of different morphology and chemical composition are distinguished along the grain boundaries. The microhardness of the alloy decreases to ~ 4800 MPa. The structure of the AlNiCoFeCrCu alloy after arc melting is microcrystalline dendritic. The distribution of chemical elements throughout the alloy volume is non-uniform. Copper predominates in the dendrites. The interdendritic region has a Widmanstatten structure. Two types of structures are realized in the ingot: phases of the B2 type (in the matrix space) and phases of the A1 type (in the dendrites). The microhardness of the alloy is ~ 6500 MPa. When the alloy is heated to 1650°C, three endothermic processes occurring in the sample are recorded on the DTA thermogram. During subsequent solidification at a rate of 1 deg/s, a structure with two types of dendrites with a substructure is formed. The dendrites differ in size, shape and element content. The interdendritic space, as well as in the sample after arc melting, is represented by a Widmanstatten structure, but the dimensions of the plates are an order of magnitude higher. During crystallization, stratification occurs simultaneously in the dendrites and interdendritic space with the release of several phases of different composition and morphology. The microhardness of the alloy decreases to ~ 5000 MPa.
Russian Metallurgy. 2025;(5):5–16
5–16
THE STRUCTURE OF THE Al70Cu30 ALLOY AFTER CRYSTALLIZATION FROM THE LIQUID PHASE AT EXTREME PRESSURES
Аннотация
A comparative study of Al70Cu30 binary alloy samples obtained from the liquid phase at normal and high pressures of 3–5, 7, 8, and 10 GPa was performed using metallographic and X-ray diffraction analyses using electron microscopy. The melt temperature before quenching is 1100 and 1300 °C, the cooling rate is ~1000 °C/s. Two phases were revealed in the structure of all the obtained samples: α-Al (cubic, cF4/1) and Al2Cu (tetra, tI12/2). When solidified under a pressure of 3–4 GPa, the structure is crushed, compared with the original ingot obtained at normal pressure, the morphology of the structural components of the alloy changes. Changing the pressure from 5 to 8 GPa leads to additional refinement of the alloy microstructure. Crystallization occurs with the formation of solid solutions with a high copper content in aluminum. A pressure of 10 GPa promotes the formation of quasi-entectic in the alloy. The selected thermobaric action modes lead to an increase in the hardness of the samples, which is due to the refinement of the microstructure and the formation of solid solutions in the alloy.
Russian Metallurgy. 2025;(5):17–25
17–25
INVESTIGATION OF THE INFLUENCE OF SELECTIVE LASER MELTING PARAMETRES ON THE STRUCTURE AND MECHANICAL PROPERTIES OF Al-Ce-Fe-Ni-Zr ALLOY
Аннотация
Samples of Al-Ce-Fe-Ni-Zr alloy were obtained by selective laser melting at scanning speeds of 700–1900 mm/s. The structure of the samples is eutectic: a solid solution based on aluminum is located inside intermetallic cells. A coarser eutectic structure with coarser cells is observed at the cell boundary. The microhardness of the samples was HV0,1 = 115–170, the tensile strength was 370–475 MPa, and the ductility was 10–23%. Residual thermal stresses <250 MPa were observed in the samples. An increase in energy density contributed to a decrease in strength characteristics, an increase in elongation, and a decrease in residual stress.
Russian Metallurgy. 2025;(5):26–32
26–32
STUDY OF THE COMPOSITION AND PROPERTIES OF VT6 ALLOY GRANULES OBTAINED BY CENTRIFUGAL PLASMA SPRAYING
Аннотация
Mathematical modeling of the motion and cooling rates of VT6 alloy powders (granules) obtained from an ingot by plasma-centrifugal spraying is performed. Calculations are performed for particles with diameters of 30, 50 and 70 µm in an inert gas environment of 90% He-10% Ar at an electrode rotation speed of 25000 min-1. It is shown that molten particles of all sizes solidify at close distances (~10 cm) from the molten electrode surface. The particle cooling rates at the initial stage of motion reach values of 3.6 105–1.5 106 K/s. The time intervals of particle crystallization (their complete solidification) were ~0.3–1 ms. Changes in the microstructure, microhardness, chemical and phase compositions of VT6 alloy granules obtained after separation into three fractions are studied. Using X-ray microanalysis in SEM, a uniform distribution of the main elements over the granule cross-section was noted, as well as a slight difference in the chemical composition of different fractions, which generally indicates the homogeneity of the obtained powder. It was shown that the structure of particles of different fractions differs in the parameters of the crystal lattice and is a mixture of two solid solutions, which is probably due to the difference in cooling rates and the content of alloying components. It was noted that in granules after centrifugal spraying, the microhardness values increase (compared to the original ingot), while with an increase in the average diameter of the particles, the average microhardness values decrease.
Russian Metallurgy. 2025;(5):33–42
33–42
ASPECTS OF CARBON DIOXIDE CORROSION IN MODERN PIPE STEELS
Аннотация
This study investigates the corrosion behavior of pipe steels with chromium content up to 17% in CO2-containing environments. Weight loss method was used to evaluate the key factors influencing corrosion processes, including temperature (up to 150 °C), CO2 partial pressure (up to 170 atm), chloride-ion concentration (up to 240 g/L), solution pH (3.5–7.5), and H2S partial pressure (up to 0.5 atm). Results indicate that steels containing less than 1% Cr cannot provide required corrosion resistance. Increasing chromium content to 3–5% has a negligible effect on corrosion rates under these conditions, whereas steels with 13% Cr or higher demonstrate significantly improved resistance, even under highly aggressive conditions. This enhanced performance correlates with changes in the composition and protective properties of surface corrosion product layers. The findings establish application limits for steels with varying chromium content in CO2 environments and provide a foundation for material selection guidelines in extreme operating conditions.
Russian Metallurgy. 2025;(5):43-51
43-51
EFFECT OF LOW MANGANESE AND PHOSPHORUS CONTENTS ON THE BULK AND SURFACE PROPERTIES OF IRON MELTS
Аннотация
There are virtually no published data on the combined effect of the impurities accompanying the dephosphorization process on the structural and physicochemical properties of iron melts. The state of the iron melt was considered as a function of composition and the corresponding values of density and surface tension based on the conditions of metal refining from phosphorus in the presence of manganese. The effect of these elements on the structural and physicochemical properties of melt was estimated according to the density and surface tension in the form of temperature and concentration dependence. In the manganese- and phosphorus-containing melts, compression effects and negative deviations from Raoult's law were observed. A decrease in the surface tension in the iron melts containing phosphorus and manganese was found. The addition of manganese to the iron melt had the opposite effect with respect to decreasing the surface tension and formation of the higher density.
Russian Metallurgy. 2025;(5):52-60
52-60
Inconel 625/(WC, W2C) COMPOSITE COATINGS SYNTHESIZED BY LASER CLADDING
Аннотация
A study of the phase structure state of Inconel 625/WC composite coatings synthesized by laser cladding has been carried out. During the synthesis of experimental coatings, the content of the hardening phase was varied in the range of 10 to 50 vol.%. X-ray diffraction shows that the phase composition of the coatings is represented by nickel solid solution and carbide phases WC, W2C, η1(Ni3Mo3C) and MoNbC2. By means of scanning electron microscopy and microspectral X-ray analysis in the structure of coatings were revealed spherical particles of initial tungsten carbide, around them "halo" enriched with W, C, as well as carbide-forming elements of matrix Mo, Nb and Cr, dendrites of nickel matrix and interdendritic space partly with eutectic structure, partly with excessive separations, enriched with Mo, Nb, Cr and W. It is found that the lattice parameter of the nickel solid solution depends non-monotonically on the carbide content in the coating: its maximum value is observed at 30% of tungsten carbide. It is shown that the main mechanism of hardening of the coating matrix is dispersive due to the release of η1(Ni3Mo3C) phase.
Russian Metallurgy. 2025;(5):61-69
61-69
EXPERIENCE IN OBTAINING AND USING SHS LIGATURES BASED ON CHROMIUM NITRIDES FOR SMELTING STAINLESS STEEL
Аннотация
A brief overview of the current global production of stainless steels is provided. It is shown that in China, the leading producer of stainless steel, the share of nitrogen-containing stainless metal smelting in 2023 exceeded 30% and amounted to 11.5 million tons. For alloying such metal with nitrogen, chromium nitride-based ligatures are in demand – nitrided metallic chromium and nitrided ferrochrome. This paper presents the experience of obtaining low-carbon chromium-based ligatures with an increased nitrogen content using the SHS method. The design of a special flow-through SHS reactor is proposed and a technology for nitriding aluminothermic chromium and ferrochrome powders with a particle size of up to 400 μm in a reacting gas flow is developed. As a result of the experimental studies, the fundamental possibility of their nitriding in the co-combustion mode was established and the dependences of the combustion rate and nitrogen content in the synthesis products on the pressure and flow rate of the reacting gas were revealed. Tests of the synthesized high-nitrogen ferrochrome were conducted during the experimental smelting of duplex steel UNS S32750 (Super Duplex 25Cr) under the conditions of the Zlatoust Metallurgical Plant. The results of the pilot industrial smelting of the metal showed that the developed alloying material provides a stable nitrogen concentration in the metal, within 0.28–0.30 mass %, with the actual nitrogen absorption by the steel melt of 82–86%.
Russian Metallurgy. 2025;(5):70-77
70-77
PRODUCTION OF W-Y2O3 POWDERS WITH SPHERICAL PARTICLES AND SUBMICRON INTERNAL STRUCTURE USING ELECTRIC ARC THERMAL PLASMA
Аннотация
This paper presents the results of the study of the process of obtaining spheroidized powders of the W-Y2O3 system of 5–50 μm fraction, the particles of which are characterized by submicron grain size of tungsten and uniform distribution of yttrium oxide. The powders were obtained using an approach involving successive stages of plasma-chemical synthesis of nanopowders of the W-Y2O3 system, granulation of nanopowders by spray drying and plasma spheroidization of the obtained microgranules. The regularities of formation of composite nanopowders W-Y2O3 with yttrium oxide content in the range from 0.3 to 5.0 wt.% in the flow of nitrogen-hydrogen plasma have been established. The parameters and conditions of plasma-chemical synthesis have been determined, under which the complete transformation of initial reagents into target products (W and Y2O3) with uniform distribution of yttrium oxide in synthesized nanopowders is achieved. The conditions of preparation of stable suspensions based on nanopowders of W-Y2O3 system and the process of their spray drying, providing the formation of predominantly rounded nanopowder microgranules of fraction −60 microns with maximum yield and productivity have been determined. The influence of plasma treatment parameters on the degree of spheroidization, internal structure, bulk density and fluidity of microorganisms has been established, and the possible ranges of variation of these characteristics have been determined. It is proved that the uniformity of yttrium oxide distribution in powder materials is provided at all stages of obtaining spheroidized microparticles of W-Y2O3 system – from plasma-chemical synthesis of nanopowders to processing of microgranules in the flow of electric arc thermal plasma. The possibility of significant refining of treated microgranules by gas impurities (O, N, H, C) during plasma treatment is demonstrated.
Russian Metallurgy. 2025;(5):78-90
78-90
INTERACTION OF LIQUID SLAG CaO-Al2O3-SiO2-MgO WITH THE Al2O3-BASED REFRACTORY CERAMICS
Аннотация
The sessile drop method was used to study the interaction of liquid slag CaO-Al2O3-SiO2-MgO with the Al2O3-based refractory material. A decrease in the wetting angle to 15° in the initial 10 min of the experiment and the reduction to 6° for the next 110 min were found. The microstructure and elemental mapping of cross sections of the slag and ceramics were examined. The phase corresponding to CaAl12O19 at the grain boundaries of aluminum oxide in the refractory ceramics was formed. Its fraction in the initial ceramics was about 9% mass., whereas after experiment it was close to 25% mass. This indicates a chemical interaction of slag with the ceramics. In the central zone of interaction, a slag penetration into the ceramics was observed.
Russian Metallurgy. 2025;(5):91-98
91-98