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In the article, investigation is carried out at the second stage of aluminizing, when a consistent substance containing aluminium powder (the first option) or graphite powder and aluminium powder (the second option) is applied to the surface that has undergone aluminizing at the first stage, before further electrospark alloying with an aluminium electrode, and, regardless of the drying of the consistent substance, the aluminizing process is carried out at a discharge energy of 0.52-2.6 J and a productivity of 1.0-2.0 cm2/min, while the discharge energy and productivity are chosen such that the surface roughness decreases by ≅ 3-4 times. At the second stage aluminizing for both options, when using a consistent substance that contains aluminium powder or aluminium powder and graphite powder, the microhardness of the 'white layer' and the diffusion zone are increased (to a greater degree when graphite is present in the consistent substance), the surface roughness is decreased, and the integrity of the coating is of 100%. Before practical implementation, it is recommended to carry out the aluminizing process according to the first option at the discharge energy Wр = 4.6-6.8 J, using a consistent substance containing aluminium powder and graphite powder at the second stage. [ABSTRACT FROM AUTHOR]

The structure formation and properties of the surface layers of steel parts after alloying by traditional technologies and the method of electrospark alloying (ESA) is analysed in the article. As a result of the study of the productivity of the ESA process by aluminium electrode-tool, which is one of the important parameters of the ESA technology, reserves are revealed for improving the quality of the surface layers of steel parts during aluminizing. Two options for reducing productivity in relation to the traditional are studied: the first one, when productivity is reduced by ≅ 2 times; the second one, when performance is reduced by ≅ 4 times. As established, in the first variant, when the discharge energy increases from 0.52 to 6.8 J, at the first stage of aluminizing of steel 20 and steel 40, the thickness of the 'white' layer from 20 to 75 and from 25 to 110 μm, respectively; the thickness of the diffusion zone increases from 35 to 120 and from 40 to 140 μm, respectively; the microhardness of the 'white layer' increases from 2200 to 7400 and from 2400 to 7450 MPa, respectively; the surface roughness Ra increases from 1.1 to 9.0 and from 1.0 to 8.1 μm, respectively, and the continuity increases from 80 to 100% starting with Wр = 4.6 J and from 60 to 100% at Wр = 6.8 J. In the second variant, when the discharge energy increases from 0.52 to 6.8 J, at the first stage of processing steel 20 and steel 40, the thickness of the 'white' layer increases for steel 20 from 25 to 60 μm at Wp = 4.6 J, and then it doesn't change for steel 40 from 30 to 100 μm; the thickness of the diffusion zone increases from 45 to 130, respectively; the microhardness of the 'white layer' increases from 2250 to 7300 and from 2450 to 7300 MPa, respectively; the surface roughness Ra increases from 1.3 to 9.0 and from 1.6 to 8.1 μm, respectively, and the continuity for both steel 20 and steel 40 at Wр = 0.52 J is of 95% and further increases to 100%. [ABSTRACT FROM AUTHOR]

The analysis of the influence of the parameters of electrospark alloying with an aluminium electrode on the quality (roughness, microstructure of the coating, its continuity, phase composition, and microhardness) of the aluminized layer is presented. the effect of finishing methods after aluminizing is evaluated. the heat resistance of the obtained coatings is studied. Metallographic analysis shows that the coating consists of three sections: a 'white' layer, a diffusion zone, and the base metal. With an increase in the discharge energy, such quality parameters of the surface layer as thickness, microhardness of both a 'white' layer and a transition zone, and roughness are increased. The continuity of a 'white' layer at the discharge energy Wp = 0.52 J is low (of 50-60%); with a subsequent increase in the discharge energy, it increases and, at Wp = 6.8 J, it is of 100%. An increase in the discharge energy during electric-spark alloying (ESA) leads to a change in the chemical and phase compositions of the layer: at low discharge energies, a layer is formed, consisting mainly of α-Fe and aluminium oxides. As Wp increases, the layer consists of iron and aluminium intermetallic compounds, as well as free aluminium, that is confirmed by the data of local x-ray microanalysis. For practical application, it is possible to recommend the process of aluminizing by the ESA method, using the modes (discharge energy in the range of 4.6-6.8 J and productivity of 2.0-3.0 cm²/min). Such process provides the formation of a 'white' layer with a thickness of 70-130 µm, microhardness of 5000-7500 MPa, roughness (Ra) of 6-9 µm, and continuity of 95100%. In order to increase the thickness of the aluminized layer, it is recommended to preliminarily apply grease containing aluminium powder to the steel surface and, without waiting for it to dry, carry out ESA with an aluminium electrode. In this case, the coating continuity is of 100%, the layer thickness is of up to 200 pm, and the microhardness is of 4500 MPa. The paper presents the results of study of the quality parameters of multicomponent aluminium-containing coatings of Al-S, Al-C-S, and Al-C-B systems. Replacing the aluminium electrode with graphite one leads to a decrease in the thickness and continuity of a 'white' layer, respectively, to 50 µm and 30%. In turn, the microhardness on the surface increases to 9000 MPa. The addition of 0.7 boron to the consistency substance leads to an increase in the thickness and continuity of a 'white' layer, respectively, up to 60 µm and 70%. The microhardness on the surface rises to 12000 MPa. In order to reduce the roughness of the surface layer and to obtain continuous coatings, it is recommended to carry out ESA with an aluminium electrode, but at lower modes. [ABSTRACT FROM AUTHOR]

Copyright of Metallophysics & Advanced Technologies / Metallofizika i Novejsie Tehnologii is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Metallophysics & Advanced Technologies / Metallofizika i Novejsie Tehnologii is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)