Development Of Magnesium Alloy Microarc Oxidation Pulse Power Supply With Discharge Loop

Micro-Arc Oxidation is a new surface treatment technique,developed from anodic oxidation,which used micro-arc discharge in the metal oxide ceramic membrane.In this paper,we discuss mechanism of micro-discharge and model of micro-arc oxidation, which based on the test platform which build with self-developed high-power, multi-output of the pulse;the techniques requirement and phenomenon and the grown progress of ceramic membrane.Design a new typical power according as the requirement which bring forward based on system load characteristic.Study showed Micro-arc oxidation process can be divided into three stages,named: anodic oxidation,the spark discharge and the micro-arc oxidation stages.Ceramic layer was mainly components by metal oxide which formed by a series of micro-discharge.Non-balance metal oxide film can be made by discharge in small extent in the progress of fast hot and then fast cool.Micro-arc discharge can be divided into four stages,named:electrolyte,discharge,oxidation and cooling.The necessary condition of arc-discharge happening is exist of oxygen on the magnesium alloy surface and the oxygen endured definite electric field.Forming Micro-arc Oxidation film must have five conditions,it contains:electrolyte,initialization film,high-handed electric field and the oxygen produced by electrolyze water.According to collect and analyze signals of voltage and current.Found that:the increase of load impedance is gradually along with time.And then educe a curve of system impedance-deal time in the condition of frequency 700 and pulse duty 20%by MATLAB.Study showed that:The load characteristic of Micro-arc Oxidation can be replaced by RC circuit.And then educe a formula which between film thickness and techniques parameter.We can find that the typical of power have a key function in the progress of magnesium alloy Micro-arc Oxidation when we tried different power contain:direct current,AC pulse power,DC pulse power and discharge current pulse power.The discharge current pulse power has a good effect because it can abolish big arc effectually.Find that the film grown fast in the invariableness current modal when we study the film speed between invariableness voltage and invariableness current. The best match time between pulse action and cooling is 1:4 in the condition of pulse frequency 700Hz.The study of load characteristic showed that:the mostly characteristic are resistance and capacitance.The problem of arc persistence burning can be settled by importing the discharge current.According this we design a new typical power with discharge current.This power come true pulse discharge alternation with IGBT in series;come true output great power with IGBT parallel connection.The control system core is 80C196KB which high speed input gob can be used to collect in-phase signal and output high speed IGBT drive signal;invariableness voltage and invariableness current output characteristic can be obtained by figure PI adjusted.The sample power has a good characteristic of credibility in the circulating.