STUDYING STABILITY PROPERTIES OF PROTECTIVE COATINGS FORMED BY MICROARC OXIDATION FOR WORKPIECE GROUP PROCESSING

The paper studies performance reproduction stability for protective coatings formed by microarc oxidation (MAO) when processing the  group of workpieces. Ceramic-like MAO coatings exhibit high  resistance to wear, corrosion, shock temperature impact while featuring high adhesive strength. At the same time, an  essential indicator of any technological process is the stability of its  results. In general, most research findings published in the MAO field disregard the analysis of stability of obtained results and fail to study the effect that technological factors have on this parameter. This  paper is the first one that provides experimental reproduction  stability estimates for the key characteristics (thickness, through  porosity and microhardness) of MAO coatings formed while  processing  the group of workpieces and for electrolyte exhaustion  effect on the values of these characteristics. The studies allow for a  conclusion that the stability of these MAO coating indicators depends  largely on electrolyte exhaustion and the time of microarc  oxidation process. It is noted that values of these characteristics can  significantly differ for coatings formed simultaneously on workpieces in the same group, and the stability of coating characteristics  (thickness, through porosity and microhardness) increases with an increase in MAO processing time. The results also prove the  assumption about changes in the characteristics of coatings formed when processing the group of workpieces are due to unevenly  distributed electric current density between these workpieces and resulting unequal electricity amount flowed in the galvanic circuit,  that determines the formation of the coating substrate.

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