Russian Metallurgy (Metally)最新文献

Abstract—The influence of heat and vibration treatment on the structure and mechanical properties of experimental specimens prepared from an ER70-S6 welding wire by additive electric arc growth is considered. Based on the results of impact strength tests, the cold resistance of the experimental specimens is estimated. Electron microscopy is used to analyze the microstructure of the material and to calculate the grain size. Heat treatment and vibration treatment are shown to significantly increase the cold resistance of the materials produced by electric arc cladding. Replacement of heat treatment operations is possible by introducing the function of vibration treatment of a weld pool into hybrid machining centers.

The oxidation resistance of a coating, which is formed by firing deposition of layers from a ZrSi₂–MoSi₂–ZrB₂–Si powder mixture, on a C/C–SiC composite substrate is studied. Oxidation resistance tests are carried out under interaction with a high-speed air plasma flow at temperatures up to 2200°C. The performance of the coating is ensured by the formation (and evolution during operation) of a heterogeneous oxide film based on borosilicate glass modified with zirconium, which is an efficient barrier to oxygen diffusion and promotes the passivation of oxidation processes. An increase in the operating temperatures above 1750–1800°C leads to glass phase evaporation from the surface and the formation of a porous thermal barrier layer based on ZrO₂ and containing secondary phases Mo/MoO₂, Mo₃Si, and Mo₅Si₃. The temperature gradient across the coating thickness favors partial preservation of the glass phase in the inner layers due to a decrease in the vapor pressure, which results in the retardation of oxygen diffusion deep into the material. The temperature–time ranges of performance; the characteristics of mass loss, catalytic activity, and emissivity of the coating; and the main factors limiting the efficiency of its protective action are determined.

The results of developing a (Co–Cr–Si) + (Cr–Al) diffusion coating using a two-stage powder method are presented. The mechanisms of transfer of cobalt, chromium, silicon, and aluminum atoms to the surface of a ZhS6U superalloy at the first and second stages of processing are discussed. The characteristics of the composition, structure, and life of the (Co–Cr–Si) + (Cr–Al) coating are determined at a temperature of 900°C under corrosion conditions in the presence of an aggressive salt deposit.

Abstract—The effect of the scale factor on the elastic modulus determined by instrumented indentation in the elastic and elastoplastic regions of indentation diagrams has been studied. A significant increase in the elastic modulus has been established upon transition to micro- and nanoscale indentation. The reasons for the effect of the scale factor on the elastic modulus determined by instrumented indentation are outlined.

A number of materials are presented, the purpose of which is to substantiate, including the use of experimental methods, the expediency and prospects of using bimetallic blanks for the production of harrower disks, and ultrajet diagnostics is proposed as a means of their rapid quality assessment. The importance of the research topic is proved by analyzing information sources related to the study of the creation of tillage tools. By conducting friction and wear-resistant tests of samples and using the results of ultrajet diagnostics, we demonstrate that a bimetallic tool can provide an increased service life and a number of operational properties, such as self-sharpening. In conclusion, we formulate some general trends for continuing investigations, the need for which is justified by the positive results of preliminary experimental data demonstrated in the article.

Abstract—The acidic, alkaline, and soda leaching of spent petrochemical catalysts to extract vanadium oxide is studied. The most efficient reagent, its consumption, leaching time, and temperature of the pulp are chosen using experimental results. The degree of extraction of vanadium oxide to the solution has been achieved at a level of 80% for a solution of sodium hydroxide (200 g/L) as a reagent, the solid-to-liquid ratio S : L = 1 : 3, a pulp temperature of 100°C, and a process time of about 3 h.

A steady-state numerical model has been developed for the working zone of an A-550 electroslag remelting pilot furnace operating at dc with changing polarity. The model consists of a software physical solver and a computational grid. A mathematical apparatus consisting of electric and thermodynamic components has been designed. The list of the properties of the involved substances and materials is presented. The numerical fields of the current density, heat, and temperature distributions over the slag pool thickness are calculated.

The kinetics of hydrogenation of a two-phase deformed alloy based on the Ti₂AlNb intermetallic compound in a temperature range of 700–900°C and the effect of hydrogen content and heating temperature on the formation of phase composition and structure are studied. Active and uniform hydrogen absorption of the alloy is shown to occur at low hydrogenation annealing temperatures. As the temperature increases, the hydrogenation intensity is found to decrease, and the growth of O-phase plates by 2–4 times is observed, which results in a decrease in the microhardness of the alloy.

The recovery of nickel and cobalt from the ferriferrous laterite ores of the Buruktal deposit via a hydrometallurgical processing scheme for the reduced ferriferrous oxidized nickel (limonite) ore with weak sulfuric acid solutions is studied. An ammonia reagent (NH₄)₂SO₄, which forms Ni and Co complexes, is used to enhance the leaching selectivity. The possibility of decreasing the consumption of H₂SO₄ and intensifying nickel and cobalt recovery at increased pH of the solution (pH 3.0–5.0) and recycling of sulfuric acid solutions is studied.

Abstract—The paper presents the results of a finite element study of the influence of friction conditions at the tool–metal contact surface on the stress–strain state of the metal in the deformation zone in cold forging of bars on a lever radial forging machine. The thus-obtained data were analyzed to give recommendations on the magnitudes of friction forces at the tool–metal contact surface in forging in order to provide rational forging protocols.