INVESTIGATION OF THE STRUCTURE AND PROPERTIES OF BOROCHROMIC LAYERS OBTAINED BY DIFFUSION SATURATION FROM COATINGS

В работе приведены результаты исследований структуры и свойств борохромированных слоев на стали 20, полученных диффузионным насыщением из обмазок. Проведен металлографический анализ и определена микротвердость на стали 20 борохромированных слоев, полученных из разных составов.

Analysis of methods for obtaining zinc-containing coatings using hot-dip galvanizing production waste

The article presents the waste generated during the production of hot-dip galvanizing. The analysis of the proposed methods of using these wastes in the production of zinc-containing coatings is carried out. It is shown that hard zinc can be successfully used in the compositions of saturating mixtures during thermal diffusion galvanizing of steel products and obtain high-quality coatings. The disadvantages include the need for grinding hard zinc.The dispersed waste of hot-dip galvanizing production, which is formed as a result of blowing pipes with superheated steam, can be used as a cheap substitute for expensive zinc powder in the compositions of zinc-filled paints. For paints, a fraction of 2–15 microns is used, which is 27 % of the total fractional composition. Therefore, in order to use a wider range of values of the fractional composition of dispersed waste to obtain zinc coatings and thus ensure the recycling of zinc into industrial circulation, the authors of this article plan to optimize and develop the compositions of powder compositions and the technology of thermal diffusion saturation of steel products based on zinc-containing waste.

Investigation of the variation in the size of samples made of 5СNM steel under thermal diffusion saturation with powder mixtures containing boron and copper

The change in the dimensions of parts after diffusion saturation of alloyed steel 5KhNM with boron and copper is investigated. Diffusion layers obtained on samples with different compositions of the saturating mixture are described. It is shown that when carrying out experiments on saturation of samples in a medium of powders with boron and copper, diffusion layers with an acicular structure with a thickness of 220...330 μm are obtained, and the increase in the observed size was from 44 to 135 μm, depending on the composition of the powder mixture. The properties of diffusion layers have been studied, including the distribution of microhardness and chemical elements at different distances from the surface.

Increase of Durability of Austenitic Steel by Overlap of Carburization and Diffusion Saturation from Liquid Metal Medium Solutions Technologies

This paper investigated the overlap of carburization and diffusion saturation from liquid metal medium solutions technologies. The carburization of austhenic steel able to increase of its wear resistance and microhardness to 700HV. But this kind of treatment provided to reduction of corrosion resistance. This effect conditioned by formation of chromium carbides, herewith austenite of steel impoverished of chromium. This paper proposes the new technology lets increase the durability of asthenic steels, using carburization and diffusion saturation in eutectic Pb-Bi-Li medium with adding of nickel and chromium. The most effective technology consisted of previous carburization, diffusion saturation and final carburization. First carburization provided to increase of surface layers microhardness to 2800 MPa, diffusion saturation to 7500 MPa, the final carburization to 19500 MPa. The properties of coating depended of combination of technological impact and technological modes of every stage of technological process: temperature and duration. The temperature influenced to microhardness of coating: when the temperature increased microhardness decreased. The duration of diffusion saturation influenced to thickness of diffusion layer: when the duration increased the thickness increased too

Simulation of the Carbon Diffusion Saturation Gear from 15Cr2 Steel in the Cementation Process

The studies on cementation focus exclusively on the carbon’s movement. It is described by diffusion equations, often with constant coefficients and without regard to the liaising with temperature. It does not allow to have regard to the further carbon diffusion into the workpiece with the lower temperature range. The most accurate prediction of carbon concentration profiles depending on the parameters of the carburization regime and the chemical composition of steel is possible with the mathematical models using. However, most models show good results for Fe-C austenite without affecting the effect of alloying substitution elements. Taking into account the influence of alloying elements leads to complex empirical dependencies with difficult selected coefficients. It makes their use difficult. The study describes the simulation using the finite element method for the process of austenite’s diffusion saturation Fe-C-Cr system with carbon during cementation. Here is an example of a steel gear 15Cr2 with the temperature influence. The COMSOL Multiphysics program is used to solve the problem numerically. It is found that the model of carbon diffusion in unalloyed austenite for the single-stage cementation regime is in good contact with the experimental data for the Fe-C-Cr austenite of 15Cr2 steel. For a two-stage process, the calculation of the carbon concentration in the surface layer has a slightly greater deviation from the experimental data than it is at a greater depth.

Using the Diffusion Saturation Technology for the Surface of Different Steel Products from Melts of Low-Melting Metals

The article discusses the modern method of increasing the corrosion and wear resistance of machine parts by diffusion saturation from the environment of fusible melts. A review of ongoing studies is on the multicomponent diffusion saturation of steel samples, including refractory metals. The results of the studies will be the basis for the formation of a coating with increased resistance to corrosion and strength of the surface layer.