EXPERIMENTAL STUDY TO DETERMINE THE OPTIMAL COMPOSITION AND THICKNESS OF THE SPRAYED LAYER FOR FURTHER IMPLEMENTATION OF THE MAO PROCESS

Abstract

The analysis of literary sources has shown the prospects and the technical possibility of restoring and strengthening parts of agricultural machinery with combined technology using methods of gas-thermal spraying and micro-arc oxidation. The use of base materials made of alloys not used in micro-arc oxidation necessitates the determination of the minimum allowable thickness of the deposited layer for further conducting the micro-arc oxidation process. (Research purpose) The research purpose is to carry out theoretical studies of the composition and thickness of the sprayed layer; to determine experimentally the effect of modes and compositions of micro-arc oxidation electrolytes on the nature and morphology of the surface of the base–coating transition zone. (Materials and methods) The anode-cathode method of micro-arc oxidation was used. The following parameters are variable: in solution – the concentration of caustic potassium KOH and sodium metasilicate Na2SiO3, the amount of nano addition in the form of diamond powder; in technology – the time of micro-arc oxidation. Microhardness was measured using a KMT-3 microhardness meter; The thickness of the layer was determined using an OLYMPUS GX51 optical microscope at a magnification of 100 times. (Results and discussion) The features of the micro-arc oxidation process cause the presence of micro-roughness on the surface of the base metal-coating, the height of which depends on the power of the punched micro-arc and the electrolyte composition. The greatest hardness of the coating is achieved when using nano diamonds as an additive and a long processing time. (Conclusions) When restoring parts from valve metals, the minimum thickness of the deposited alloy layer after machining should be at least 150 percent of the thickness of the micro-arc oxidation layer specified in the technological process; when restoring parts from non-valve metals, at least 250 percent.