Abstract
The influence of operating parameters of plasma-electrolytic oxidation in diphosphate cobalt-containing electrolyte on the process of formation of oxide coatings on alumosilicon alloy AL25 (GOST 1583) was studied. It was shown that inclusion of cobalt into the composition of surface oxide layers leads to a change of morphology and topography of the surface. Variation of current density and PEO time allows flexible control of the process of incorporation of the catalytic component into the matrix of oxide of basic metal. It was shown that at an increase in oxidation time, cobalt content in the surface oxide layer increases. The rational mode of plasma-electrolytic treatment of piston alloy in diphosphate electrolyte for obtaining oxide coatings, enriched with cobalt, was substantiated. It is advisable to perform formation of PEO-coatings on AL25 with developed globular-mosaic surface, maximum cobalt content, with minimizing impurities in the range of current densities of 3–5 A/dm 2 within 20–40 min. The obtained cobalt-containing oxide coatings can be used in the air and water purification systems, specifically, for intracylinder catalysis of gas emissions of internal combustion engines.
Highlights
Alloying of silumins with additional components allows great expansion of the scope of their application
It should be noted that chronograms at i=3–5 A/dm2 are characterized by existence of a kink in the pre-sparking area in the time interval of 1–2 min, and in this case, a kink is more pronounced at lower current density (Fig. 1, dependence 1)
It was found that an increase in current density of the treatment within the interval of 3–10 A/dm2 leads to a decrease in the time of entering the sparking mode from 6 to 1 min, operating formation voltage is 160–170 V
Summary
Alloying of silumins with additional components allows great expansion of the scope of their application. Al-Si alloys are successfully applied in various industries, for manufacturing parts of a cylinder-piston group of internal combustion engines (ICE) [1, 2]. Additional techniques of surface modification are effectively used for improvement of mechanical properties of silumins.
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