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 coatingwas 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.

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.

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.

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.