Mixed alumina and cobalt containing plasma electrolytic oxide coatings

Principles of plasma electrolytic oxidation of the AL25 aluminum alloy in diphosphate alkali solutions containing cobalt(2+) cations are discussed. It has been established that a variation in the concentration of the electrolyte components provides the formation of mixed-oxide coatings consisting of the basic matrix materials and the cobalt oxides of different content. An increase in the cobalt oxide content in the coating is achieved by the variation in electrolysis current density as well as the treatment time due to both the electrochemical and thermo-chemical reactions at substrate surface and in spark region. Current density intervals that provide micro-globular surface formation and uniform cobalt distribution in the coating are determined. The composition and morphology of the surface causes high catalytic properties of synthesized materials, which confirmed the results of testing in model reaction CO and benzene oxidation as well as fuel combustion for various modes of engine operation

Функциональные свойства гальванических сплавов Fe−Mo и Fe−Mo−W

The influence of the modes of electrodeposition on the morphology, topography, and structure of the galvanic alloys of iron with molybdenum and tungsten is discussed. It is shown that the increase in the corrosion resistance of Fe–Mo and Fe–Mo–W coatings in acid and neutral chloride-containing media is caused both by the elevation of their passivating ability caused by the process of alloying components and by the formation of globular surfaces with homogeneous chemical composition. The microhardnesses of Fe–Mo and Fe–Mo–W galvanic alloys prove to be 2–3 times higher than the microhardnesses of the substrates made of low-alloy steel, which can be explained by the formation of amorphous structures. The results of investigations and tribological tests show that it is reasonable to apply the coatings of double and triple iron alloys in order to reduce wear in friction couples and to increase the corrosion resistance and mechanical strength of the surfaces, which makes them promising for the repair and restoration technologies.Изучено влияние методов электроосаждения на морфологию, топографию и структуру гальванических сплавов железа с молибденом и вольфрамом. Показано, что рост коррозионной стойкости покрытий Fe–Mo и Fe–Mo–W в кислых и нейтральных хлоридсодержащих средах обусловлен увеличением их способности к пассивации в присутствии легирующих компонентов и формированием глобулярной равномерной по составу поверхности. Микротвердость гальванических сплавов Fe–Mo и Fe–Mo–W возрастает в 2-3 раза по сравнению с показателем подложки из низколегированной стали за счет формирования аморфной структуры. Результаты исследований и трибологических тестов показали целесообразность применения двойных и тройных сплавов железа для снижения износа в парах трения и увеличения коррозионного сопротивления и механической прочности поверхностей, что делает их привлекательными для технологий восстановления и упрочнения поверхностей