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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.

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Static and kinetic friction of electroless Ni composite coatings

Vencl A., Jakimovska K., Ivanova B., Ruzic J., Simeonov S., Kandeva M.

Journal of Achievements in Materials and Manufacturing Engineering

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2015

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Vol. 70, nr 1

13--21

EN

Purpose: The aim of this study was to examine the static and kinetic friction of electroless Ni coatings of different surface roughening, in unlubricated contact with various counter-body materials. In particular, difference between static and kinetic coefficient of friction was analysed. Design/methodology/approach: The Ni coatings deposition was done with electroless plating process. Samples of electroless Ni coatings without and with SiC nanoparticles were heat treated at 300°C for 6 hours. The microstructure of all samples was characterized by optical microscopy. Microhardness of samples and counter-bodies were also examined. The static and kinetic coefficient of friction was measured for each coating with initial and working surface roughness. Three typical materials used in industry were chosen as a counter-body material. The possibility of stick-slip occurrence was analysed through the static and kinetic coefficients of friction difference. Findings: Obtained results show that coatings hardness has strong influence on coefficient of friction, and that slip-stick phenomenon is unlikely to occur, since the differences between static and kinetic coefficient of friction are small. Research limitations/implications: The SiC nanoparticles were added to Ni coating in order to improve the abrasive wear resistance. In the same time, presence of SiC nanoparticles slightly increases the coefficient of friction in unlubricated conditions. Originality/value: The SiC nanoparticles were added to standard electroless Ni coating, and their properties are investigated. Heat treatment was applied to achieve crystalline structure and to improve mechanical and tribological properties. Coefficient of friction testing was performed by simply and easy to operate test rig.

3

The functional atom of tribology and its application

Kandeva M., Manolova-Daneva M.

Scientific Problems of Machines Operation and Maintenance

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2009

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Vol. 44, nr 4

29-39

EN

The notion "functional atom" (FA) was created in the Center of Tribology at the Technical University of Sofia, in the field of tribology as interdisciplinary science. The functional atom is formed of 3 components similarly to the basic contact system "body-contact-counterbody". This notion assigns the central role of contacts in the interaction of bodies in nature, techniques and society. The idea for the FA is expressed in the fact that its two alternatives "body" and "counterbody" do not interact directly, but through the third body - the contact between them, and the contact networks in the whole functional space of the atom. Six postulates as basis of the model, theory and application of FA are formulated in the pressent work. The application of FA is illustrated with concrete examples: the development of the macrostructure of tribology as interdisciplinary science; formulation and using of General law of the contact interaction of bodies in the functional space of tribology - friction, wear, lubrication, contact deformation, contact conductance and capillarity. Other illustrations and applications of the model of FA in triboecology, tribotechnologies, engineering education, etc.