Russian Metallurgy (Metally)最新文献

Abstract

An analysis of the operation of furnaces for baking carbon–graphite products shows that the problem of energy saving, which is associated, first of all, with a sharp rise in the cost of energy resources, is now of particular importance. It can be partially solved not only by increasing the thermal insulation of baking furnaces, but also by improving their process control system, in particular, the measurement technique.

Abstract

The results of microstructure examination, electron-probe microanalysis, X-ray diffraction analysis, and microhardness and porosity measurements of the product fabricated by spark plasma sintering of the powder produced by electroerosion dispersion of the R18 steel waste are presented.

Abstract

The properties of the powders used in additive manufacturing (AM), including electron-beam melting, of products have been studied. Defects in powder granules and the causes of their appearance are revealed. The recycling of the powders is found to bring about the appearance of cakes and agglomerates in their composition with a slight change in the particle size distribution. The microhardness of the powder particles is found to be 20–40 MPa higher than that of the samples constructed by electron-beam melting.

Abstract

The possibility of estimating the percentage of the magnetic phase in samples with a temperature exceeding 200°C using the nondestructive induction control method is considered. It is found that the estimation of magnetic properties of a sample at different temperatures makes it possible to control the δ and γ ferrite separately. The design of the differential induction sensor that ensures an appreciable gap between the windings and the heated surface of the sample is described. The results of mathematical simulation of the magnetic field distribution in the sensor are considered; analysis of these results makes it possible to select appropriate parameters of the sensor design.

Abstract—Using high-frequency heating, we fabricate wear-resistant boride coatings on 65G steel samples under a layer of P-066 flux-based charge containing boron carbide. The wear resistance of the resulting coatings is investigated. An experimental design is used to achieve the optimum charge composition. A technological process is proposed for enhancing the strength of flat knives by HFC boriding, and the hardened knives are subjected to field tests.

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.

Abstract—The properties of an AlSi10Mg aluminum powder material are studied. Recommendations are presented on choosing heat treatment to improve the surface characteristics for producing a body-shaped part applied in an aviation engine by selective laser melting (SLM) of additive manufacturing.

Abstract

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.

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.

Abstract

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.