Corrosion and Physicomechanical Properties of the Coatings on Ak12m2mgn Alloy Formed by Plasma-Electrolytic Oxidation
- PDF / 3,837,918 Bytes
- 10 Pages / 594 x 792 pts Page_size
- 18 Downloads / 266 Views
CORROSION AND PHYSICOMECHANICAL PROPERTIES OF THE COATINGS ON AK12M2MGN ALLOY FORMED BY PLASMA-ELECTROLYTIC OXIDATION H. V. Каrакurkchi,1 M. D. Sakhnenko,1,2 M. V. Ved,1 S. I. Zyubanova,1 and I. I. Stepanova1 We propose efficient regimes of the formation of mixed-oxide conversion coatings by plasma-electrolytic oxidation (PEO) of aluminum alloys in pyrophosphate and alkaline electrolytes. It is shown that the variations of the concentrations of electrolyte components and the parameters of PEO (current density and the duration of treatment) lead to the appearance of oxide coatings formed by the material of the metal matrix and oxides of transition metals of various compositions and morphologies, which definitely affect their functional properties. Mixed oxide coatings formed as a result of PEO are characterized by microglobular structures, small sizes of conglomerates, and elevated microhardness. Moreover, they are corrosion and wear resistant. In view of the microglobular structure of the surface and the composition of Al Al 2O 3 ⋅ MnO x and Al Al 2O 3 ⋅ CoO x oxide coatings, we can expect that the obtained materials may exhibit catalytic activity in the redox reactions with participation of oxygen and, in particular, in the working processes running in internal-combustion engines.
Keywords: AK12M2MgN alloy, plasma-electrolytic oxidation, metal-oxide system, mixed oxides, corrosion resistance, microhardness.
Introduction Aluminum alloys are widely used in various branches of industry (aircraft and machine building, medicine, chemical industry, and municipal engineering). Therefore, numerous requirements are imposed on their corrosion resistance, mechanical strength, tribological and other characteristics. Thus, in particular, in order to improve the efficiency of internal-combustion engines (ICE), one can apply in-situ catalysts directly in the combustion chambers [1]. The catalysts of the process of oxidation of hydrocarbon fuel can be split into two groups: catalysts based on noble metals (most often Pd and Pt) and catalysts based on oxides of transition metals (Mn, Co, Fe, etc.), mainly on complex oxides (spinels, perovskites, and hexaluminates) [2]. At high temperatures, catalysts based on manganese oxides and characterized by high thermal lability and oxygen affinity [3] have significant advantages; moreover, its high-temperature oxides guarantee the thermal stability of catalysts and significantly increase their activity. In the ICE chambers, it is reasonable to apply the catalytic layer directly to the surfaces of pistons that are most often produced of high-alloy cast silumins and, in particular, of АK12М2MgN [4]. The method of plasma-electrolytic oxidation (PEO) [5] seems to be the most promising procedure that can be used for the formation of thin-layer coatings on passive metal surfaces. This procedure enables one to form conversion layers containing both metal oxides and the components of electrolytes (or products 1 2
“Kharkiv Polytechnic Institute” National Technical University, Kharkiv, Ukraine. Corr
Data Loading...
