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1
Content available Sintered Ni-Free Structural Alloy Steels - Processing, Properties and Microstructure
Sułowski M., Tenerowicz-Żaba M., Valov R., Petkov V.
Archives of Metallurgy and Materials
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2020
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Vol. 65, iss. 2
851--860
EN
In this paper the development and method of production of modern, Ni-free sintered structural steels containing Cr, Mn and Mo, enabling the production of structural sintered steels in industrial conditions, using safe, with low H2-content, sintering atmospheres is presented. For this purpose, the analysis of microstructure and mechanical properties of these sintered structural steels produced in different processing conditions and also the connections between the microstructure of sintered material and its mechanical properties, was presented. Following the investigations, the appropriate chemical composition of sintered Ni-free steels with properties which are comparable or even better than those of sintered structural steels containing rich and carcinogenic nickel was choosen. Additionally, in the paper the properties of electrolitically coated carbon steels were presented, as the beginning of investigation for improving the mechanical properties of alloyed, structural sintered steels.
2
Content available Electrochemical Deposition of Silver on Aluminum Alloys
Valov R., Petkov V., Valkanov S.
Archives of Foundry Engineering
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2020
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Vol. 20, iss. 2
101--104
EN
Silver coatings have a very high reflection ability. To avoid their darkening from the hydrogen sulphide in the air, a thin layer of heat-resistant colorless lacquer is applied to the coatings. Silver plating is mainly used in jewelery, optics, electronics and electrical engineering. Depending on their application the thickness of the layer may vary from 2 to 24 μm. It can be done in several ways: chemical, electrochemical, contact, etc. The most common way of silver plating is the electrochemical deposition using cyanide and non-cyanide electrolytes. The cyanide electrolytes produce light, fine crystalline, dense and plastic coatings upon silver-plating. Usually silver coatings are applied with copper or nickel intermediate layer. In order to improve the de-oxidation of the aluminum surface new chemical treatment in acid – alkaline solution was applied. Our previous research shows that the presence of diamond nanoparticles in the electrolyte increase the metal deposition. Samples were prepared from electrolyte containing 10 g/l diamond nanoparticles. Their properties were compared to the properties of reference samples. The diamonds were obtained by detonation synthesis. The aim of this study is to obtain electrochemically deposited silver layer with high density, adhesion and electric conductivity on aluminum alloys substrate. The coating was directly plated without intermediate layer. Non-cyanide electrolyte composition and electrochemical parameters were determined in order to produce Ag coatings on Al alloy substrate without intermediate layer. The coating is with good adhesion, density and thickness of 14-23 μm.
3
Content available Characteristics and Properties of Chromium Coatings with Diamond Nanoparticles Deposited Directly on Aluminum Alloys
Petkov V., Valov R., Simeonova S., Kandeva M.
Archives of Foundry Engineering
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2020
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Vol. 20, iss. 4
115--120
EN
The objective of this study was to deposit directly chromium with diamond nanoparticles (ND) on aluminum alloys and investigate the coating surface. The chromium coatings on aluminum alloys were obtained by electrochemical deposition. The coatings were doped with ND. The diamond nanoparticles were obtained by detonation synthesis. Chromium coatings were deposited on aluminum alloys with a silicon content of 7 % and 10 %. The ND concentration in the electrolyte was 25 g/l. The surface analysis was performed by means of Atomic force microscopy. The surface of the coating of chromium with ND on Al10Si is twice more even than that on Al7Si. The microstructure and microhardness were examined with a metallographic microscope and a microhardness tester. The microhardness of the coated samples is 9163 MPa compared to 893 MPa of uncoated aluminum samples. The thickness of the chromium coatings doped with diamond nanoparticles is between 45 – 55 μm. The coatings are dense, continuous and uniform with good adhesion to the substrate material.
4
Content available Sintered Steels Coated with a Chromium Layer Doped with Diamond Nanoparticles
Petkov V., Valov R., Witkowska M., Madej M., Cempura G., Sułowski M.
Archives of Metallurgy and Materials
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2019
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Vol. 64, iss. 4
1633--1638
EN
Electrochemical Cr coatings doped with diamond nanoparticles were deposited on sintered steels with different carbon contents (0.2-0.8 wt.-%). The mechanical properties of surfaces as hardness and wear resistance increase as compared to the steel substrate. Microcutting and microgridding mechanisms were observed after tribological tests, but also adhesive wear in some areas was observed. X-ray examination indicated that the layer was textured, with the exception of the sample with the highest concentration of diamond nanoparticles in the electrolyte (42 g/l). The intensity ratio ICr110/ICr200 was calculated and compared with the indices for a standard sample. The greatest differences in the intensity ratio occurred for the samples with low carbon content (0.2% C). On the other hand, more the material is textured the greater the difference.
5
Content available Nanocomposite chromium coatings on aluminum alloys
Gidikova N., Valov R., Petkov V., Sułowski M., Witkowska M., Cempura G.
Prace Instytutu Odlewnictwa
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2017
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Vol. 57, no. 4
241--244
EN
Chromium coatings modified with nanodiamond particles were deposited on aluminum alloys. The concentration of the nanodiamond particles in the chrome plating electrolyte was from 5 to 25 g/l. The thickness of the layer varied between 30 and 70 μm. The layers were prepared with the same electrolytic conditions and were measured with a metallographic microscope. The maximum microhardness of the coating was 840 kg/mm2. X-ray diffraction analysis was performed with a Siemens D500 apparatus using the Bragg-Brentano technique. The distribution of Cr, Al and O in the cross section was studied by SEM-EDS. It was found that the layers were homogenous – only consisted of chromium. The coatings were also studied for non-destructivity by X-ray 3D computed tomography. It was found that the coatings were intact and continuous along the section. In order to obtain the maximum yield of chromium and maximum thickness of the layer, the optimum nanodiamond particle concentration was 10 g/l.
6
Content available Electrolyte coatings of chromium with nanodiamonds on sintered steels
Gidikova N., Valov R., Petkov V., Salamci E., Bilgili Z., Unal R.
Prace Instytutu Odlewnictwa
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2017
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Vol. 57, no. 4
333--336
EN
Sintered ferrous components were coated with electrochemical chromium coatings modified with nanodiamond particles. The nanodiamond particles were produced by detonation synthesis with an average grain size 8 nm. The objective of this study was to determine the tribological properties and the corrosion resistance of sintered iron samples coated with an electrochemically deposited chromium layer modified with nanodiamond particles. The thickness of the obtained composite coatings was more than 25 μm. The microstructure and microhardness were determined by metallographic methods. The mechanical and chemical properties of the samples were compared to uncoated samples prepared from the same iron powder. The microhardness was 5 times higher, the wear resistance increased 6 times and the corrosion resistance in 0.1 M NaCl solution was 10 times higher.
7
Content available Cermet composite material based on aluminothermy
Penkov I., Petkov V., Valov R.
Prace Instytutu Odlewnictwa
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2017
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Vol. 57, no. 4
293--296
EN
A new method for synthesis of cermet composite materials was developed based on aluminothermy. Employing this method a cermet composite material with a high content of AlN crystal phase was synthesized. Fine powders of aluminum and silica glass were mixed and heated in a corundum crucible for 6 hours at 1100°C in air. The X-ray diffraction analysis showed that the composite material thus synthesized contains a high concentration of AlN particles (about 33 vol. %) embedded in an aluminum silicon alloy. A small amount of Al2O3 particles (about 8 vol. %) was also found. The method proposed can also be used for synthesis of aluminum matrix composite materials containing, besides AlN, other ceramic reinforcement phases. The properties of these composite materials can be tailored by choosing an appropriate composition of the initial powder mixture for aluminothermic synthesis.
8
Content available Composite Coatings of Chromium and Nanodiamond Particles on Steel
Gidikova N., Sulowski M., Petkov V., Valov R., Cempura G.
Archives of Metallurgy and Materials
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2017
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Vol. 62, iss. 4
2421--2424
EN
Chrome plating is used to improve the properties of metal surfaces like hardness, corrosion resistance and wear resistance in machine building. To further improve these properties, an electrodeposited chromium coating on steel, modified with nanodiamond particles is proposed. The nanodiamond particles (average size 4 nm measured by TEM) are produced by detonation synthesis (NDDS). The composite coating (Cr+NDDS) has an increased thickness, about two times greater microhardness and finer micro-structure compared to that of unmodified chromium coating obtained under the same galvanization conditions. In the microstructure of specimen obtained from chrome electrolyte with concentration of NDDS 25 g/l or more, “minisections” with chromium shell were found. They were identified by metallographic microscope and X-ray analyser on etched section of chromium plated sample. The object of further research is the dependence of the presence of NDDS in the composite coating from the nanodiamond particles concentration in the chroming electrolyte.
9
Content available Wear Resistant Chromium Coatings Modified with Diamond Nanoparticles
Gidikova N., Ciaś A., Petkov V., Madej M., Sułowski M., Valov R.
Archives of Metallurgy and Materials
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2014
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Vol. 59, iss. 4
1513--1516
EN
Electrochemical chromium coatings on steel, modified with diamond nanoparticles (NDDS), were produced by detonation synthesis. Their particle size was from 10 to 50 nm. Galvanization conditions, current density, etc., concentration of NDDS, were studied in relation to the characteristics of the chromium coatings. The optimal conditions were determined to attain the maximal values of the physical and mechanical properties of the coating. Surface topography after wear testing was examined. Compared to unmodified chromium coating, microhardness of the surface increased to 1100 kg/mm2 , wear resistance, expressed as % of mass loss, increased from 3 to 10 times.
PL
Powłoki chromowe, wytworzone elektrochemicznie na stali, modyfikowane nanocząstkami diamentu, zostały wyprodukowane w procesie syntezy detonacyjnej. Ich wielkość czastek mieściła się w zakresie od 10 do 50 nm. W artykule przedstawiono wpływ warunków galwanizacji, gęstości katodowej prądu, koncentracji nanocząstek diamentu na grubość powłoki chromowej. Podczas badań wytypowano optymalne warunki wytwarzania, pozwalające na uzyskanie warstwy chromowej o najlepszych własnościach fizycznych oraz mechanicznych. Przeprowadzono również badania odporności na ścieranie uzyskanych warstw. Na podstawie badań stwierdzono, że w porównaniu do powłok chromowych nie modyfikowanych nanocząstkami diamentu, mikrotwardość na powierzchni wzrosła do 1100 kg/mm2 , a odporność na zużycie ścierne, wyrażona jako % ubytek masy, wzrosła od 3 do 10 razy.
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