Abstract
This paper studies the electric breakdown discharge process of micro-arc oxidation film on the surface of aluminum alloy. Based on the analysis of the AC parameters variation in the micro-arc oxidation process, the following conclusions can be drawn: The growth of oxide film can be divided into three stages, and Oxide film breakdown discharge occurs twice in the micro-arc oxidation process. The first stage is the formation and disruptive discharge of amorphous oxide film, producing the ceramic oxide granules, which belong to solid dielectric breakdown. In this stage the membrane voltage of the oxide film plays a key role; the second stage is the formation of ceramic oxide film, the ceramic oxide granules turns into porous structure oxide film in this stage; the third stage is the growth of ceramic oxide film, the gas film that forms in the oxide film’s porous structure is electric broken-down, which is the second breakdown discharge process, the current density on the oxide film surface could affect the breakdown process significantly.
Highlights
Micro-arc oxidation, called micro-plasma oxidation, is a technique to grow ceramic oxide films in micro areas with high temperature environment through complex electrochemical, plasma-chemical and thermochemical processes caused by the micro plasma discharging on the light alloy surface
According to the experimental phenomenon and the variation of electrical parameters in the process of microarc oxidation, the growth mechanism of micro-arc oxidation film can be divided into three stages. 4.1 Stage 1 Forming of amorphous oxide film
In the electrolyte side of the amorphous oxide film, a certain concentration gradient of charge is accumulated under the effect of electric field [4]; with the ignorance of the concentration between auxiliary electrode and the oxidation film, Vab can be regarded as the voltage between amorphous oxide film
Summary
Micro-arc oxidation, called micro-plasma oxidation, is a technique to grow ceramic oxide films in micro areas with high temperature environment through complex electrochemical, plasma-chemical and thermochemical processes caused by the micro plasma discharging on the light alloy surface. The ceramic films have some unique characteristics such as strong adhesive strength with substrate, good electrical insulation, corrosion resistance and high hardness, which can largely enhance the properties of alloy surface [1]. In order to study the influence of AC parameters on the oxide film breakdown process systematically and quantitatively, the test of micro-arc oxidation on the aluminum alloy is carried out by applying AC power in weak alkaline electrolyte in this paper. The top 4mm of the sample is the wire connection area which is covered by insulating material. The area of sample surface contacting with the electrolyte aqueous solution is 2.16 cm
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