Notes

Technological Characteristics and Flow of Micro-arc Oxidation of Magnesium CNC Machining Parts


Micro-arc anodizing is also known as micro-arc plasma oxidation or anode spark deposition, collectively referred to as micro-arc oxidation. It is a commonly used post-treatment in CNC machining https://www.machining-custom.com/cnc-machining/ of magnesium alloys. Plasma micro-arc discharge is generated in the anode area by alternating and direct current, and the instantaneous high-temperature sintering effect directly forms a ceramic film on the surface of the magnesium alloy in situ. The temperature of the micro-arc zone can reach more than 1000℃, so that the anodic oxide is coated on the surface of the metal magnesium alloy. This ceramic film greatly improves the hardness and density of the anodic oxide film. The thickness of the film layer can be adjusted between about 5~70μm. It can be guaranteed that after 500h in neutral salt spray, the coating adhesion reaches grade 0, and the microhardness is about 400HV. However, further coating protection is required after micro-arc oxidation. Next, VMT will explain to you the process characteristics and process of micro-arc oxidation of magnesium alloy CNC machining parts.


The characteristics of CNC machining magnesium alloy micro-arc oxidation process:

①The surface hardness of the material can be greatly enhanced under the micro-arc technology. The micro-hardness ranges from 1000 to 2000HV, up to 3000HV, which is comparable to that of cemented carbide and greatly exceeds that of high-carbon steel, high-alloy steel and high-speed tools after heat treatment. hardness of steel;

② CNC machined parts have more wear resistance after micro-arc oxidation;

③ After micro-arc oxidation, magnesium alloy CNC machining parts https://www.machining-custom.com/ have better heat resistance and corrosion resistance;

④Good insulation performance, insulation resistance can reach 100MΩ

⑤ The environment is good, the solution is environmentally friendly, and meets the requirements of environmental discharge;

⑥ For workpieces with complex shapes and restricted channels, a uniform film can be formed;

⑦ The process is stable and reliable, and the equipment is simple;

⑧ The reaction is carried out at room temperature, which is convenient to operate and easy to master;

⑨The ceramic film is grown in situ on the substrate, the bonding is firm, and the ceramic film is dense and uniform;

⑩ Small size deformation;

In addition, ion implantation technology, laser surface treatment technology and nitriding technology are all used to modify the surface of magnesium alloys in order to improve the wear resistance and corrosion resistance of magnesium alloy surfaces.


The process flow of CNC machining magnesium alloy micro-arc oxidation process:

① The reason for the micro-arc oxidation pretreatment is that the surface of aluminum, iron and other alloys is easily oxidized when placed in the air for a long time, forming a passivation film of several microns, and at the same time, the surface is easily adsorbed to the surrounding environment. The impurities in it form a surface adsorption layer. In order to ensure the comprehensive mechanical properties of the ceramic film obtained after micro-arc oxidation, the surface of the sample should be pretreated before micro-arc oxidation.

②Micro-arc oxidation process In the process of micro-arc oxidation, the sample to be oxidized is connected to the positive electrode of the power supply, immersed in the electrolyte as the anode, and the stainless steel electrolytic cell is connected to the negative electrode of the power supply as the cathode. After the power is turned on, the positive pulse voltage rises rapidly and the current drops rapidly. The sample to be oxidized as the anode begins to be anodized, producing a large number of tiny bubbles, and at the same time, a very thin passivation film is formed on the surface of the sample. When the applied pulse voltage exceeds a certain value, a layer of extremely fine and uniform discharge sparks appears on the surface of the material. This micro-area spark discharge phenomenon occurs at different positions on the surface of the sample, and finally a ceramic film layer is grown in-situ on the surface of the alloy to be oxidized. To achieve the purpose of strengthening the surface of the material.


The performance testing of the film layer includes three parts: thickness characterization, hardness characterization, morphology characterization, phase composition characterization and surface roughness characterization. The thickness of the oxidized ceramic film was detected by a German flow thickness gauge; the microhardness of the film surface was measured by a microhardness tester, and the surface, cross-sectional morphology and microstructure of the microarc oxidized ceramic film were measured by an environmental scanning electron microscope. to observe.


The above is just a summary of the VMT CNC machining factory https://www.machining-custom.com/. If you want to know more about CNC machining, you can contact us: [email protected] to negotiate with us.

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