Abstract
The object of research is the processes of the piston alloy AK12M2MgH treatment by the method of plasma electrolytic oxidation (PEO) with the formation of ceramic underlying coatings. One of the most problematic places is the influence of the chemical composition of the Al-Si alloy on the process of treatment and formation of ceramic coatings. It is established that electrochemical technologies are widely used to modify the surface of silumins by forming coating of various composition and purpose. In the course of the study it was shown that PEO of piston silumin should be carried out in alkaline complex electrolytes with the addition of manganese and/or cobalt salts. This makes it possible to homogenize the surface layer of the alloy by composition, to reduce the content of its alloying components and to create conditions for the formation of a uniform oxide coating with incorporation of the admissible components. It has been established that oxidation in pyrophosphate cobaltous solution allows obtaining mosaic structures of blue-violet color with cobalt content up to 24 at %. PEO silumin in the manganous alkaline electrolyte provides the formation of a brown-black ceramic-like layer with manganese content up to 35 at %. Consecutive PEO treatment in these solutions leads to the formation of a mixed fine-dispersed porous oxide coating with a total content of dopant 25–30 at %. Based on the research results, it has been proposed to oxidize the piston silumin in a regime of incident power to form uniform coatings with a high content of dopant. Obtained oxide systems have a developed surface and a significant content of catalytically active components. In comparison with the known methods of PEO treatment of piston silumin, the silicon content in the surface oxide layers does not exceed 3 at %, which is one of the requirements for catalytically active materials. The ceramics-like coatings show high catalytic activity in model oxidation reactions of CO and benzene and reduce the emission of toxic gas emissions from internal combustion engines. The proposed systems are promising for use in intracylindrical catalysis technologies and improving the fuel economy of engines.
Highlights
The internal combustion engine (ICE) piston is one of the most important details of a modern car that ope rates under severe conditions with significant thermal and mechanical loads
The aim of research is improvement of the treatment of piston made of silumin AK12M2MgN by the method of plasma electrolytic oxidizing producing doped cobalt and manganese ceramic like coatings
The plasma electrolytic oxidizing (PEO) treatment of the ICE pistons makes it possible to form manganese and cobalt containing ceramic like coatings with high catalytic properties
Summary
The internal combustion engine (ICE) piston is one of the most important details of a modern car that ope rates under severe conditions with significant thermal and mechanical loads. In such high-energy modes, a highly developed oxide matrix metal substrate with incorporated cations or the remelting electrolyte components forms due to the realization of electrochemical and thermochemical reactions [9, 10] Advantages of this method of surface modification is the simplicity of the process equipment, the nontoxicity of working solutions, the lack of a pre liminary preparation of the part, the possibility of efficient treatment of complex-shaped and large-sized products. PEO piston silumins expediently carry out in alkaline complex electrolytes This is for homogenization of the surface during treatment and to ensure high adhesion of the oxide coating to the substrate. The laboratory system includes a current source, an electrolytic cell with cooling and stirring of electrolyte, working electrodes and devices for monitoring process operating parameters
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