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Introduction of Micro-arc Oxidation Equipment and Technology

1、 Preface

With the development of modern industry and science and technology, people have higher and higher requirements for materials. In order to improve the comprehensive properties of materials, ceramic coating on the surface of metals and alloys can replace precious metals and alloys with cheap metal materials on the premise of ensuring the performance, At the same time, it can give raw metal some special properties that other surface strengthening technologies can't get, and broaden its application scope. Therefore, surface ceramic technology has gradually become a new direction of surface strengthening treatment, so micro arc oxidation technology has been applied.

Supported by the National Natural Science Foundation of China, the State Key Laboratory of metal materials of Xi'an Jiaotong University has carried out the research and development of plasma micro arc oxidation technology for light metals and alloys. With the joint efforts of Xi'an Yujie company and the State Key Laboratory of metal materials of Xi'an Jiaotong University, the high-tech and multifunctional micro arc oxidation equipment has been independently developed, A series of mature micro arc oxidation technology has been developed.

2、 Principle and characteristics of micro arc oxidation technology

Micro arc oxidation (MAO) is a kind of anodic oxidation method in which al, Ti, Mg, Zr, Ta, Nb and other metals or their alloys (called valve. Metal) are placed in electrolyte solution, and spark discharge is generated in the micropores on the alloy surface by means of electrochemistry. Under the joint action of thermochemistry, plasma chemistry and electrochemistry, more ceramic coatings are oxidized from the metal or alloy surface.

In the process of micro arc oxidation, the comprehensive performance of the film is greatly improved due to the use of plasma enhanced technology of anode discharge; Gas discharge occurs in the oxide pores, and the film materials are partially melted and thermally diffused; Deposition of colloidal particles; The negatively charged colloidal particles migrate into the discharge channel and undergo plasma chemical and thermochemical reactions. Due to the heating effect of the plasma, the micro arc oxidation layer can be removed γ- In addition to the short-range ordered amorphous structure of Al 2O 3 and - Al o (OH), there are also high-temperature transition phase - Al 2O 3 (corundum), in which the content of - Al 2O 3 is very important for the hardness of the deposited layer. Under the condition of pulse anodization, the pulse peak voltage, pulse time and frequency can be adjusted. In addition, many decorative films with uniform color can be obtained by using different electrolyte combinations Insulation film, thermal insulation film, optical film, and functional film applied in catalysis, medicine and bioengineering. The domestic research on micro arc oxidation started in the 1990s, and began to move towards the practical stage in the form of wear-resistant and decorative film. There is still a lot of work to be done to further expand the application field.

3、 Process and film characteristics of micro arc oxidation

The following table shows the performance index, performance and micro arc oxidation coating of LY12 micro arc oxidation

Hardness (HV) 1500 ~ 2000

Relative pore area (%) 0-40

5% salt spray test (H) 5 × one hundred and five

Maximum thickness( μ m) 50~250

Good flexibility

The uniformity and density of the coating film are uniform and dense on the inner and outer surfaces

Operating temperature: normal temperature

The treatment efficiency was 10-30 min (50 μ m)

Deoiling micro arc oxidation fine grinding in treatment process

The microstructure of the film can be easily adjusted (containing - Al2O3 γ- Al 2O 3, - Al o (OH) etc

Wide adaptability to materials: in addition to aluminum alloy (including aluminum matrix composites), it can also form ceramic layer on the surface of Ti, Mg, Zr, Ta, Nb and other metals and their alloys

4、 The technical features of the system are as follows

1. Multifunctional micro arc oxidation equipment:

(1) Power system:

Frequency: 15Hz ~ 9000 Hz, continuously adjustable

Duty cycle: 5-48% continuously adjustable

Power: forward working current / voltage: 400A / 700V, reverse working current / voltage: 200A / 300V

Pulse: positive and negative continuously adjustable, all digital instruments, with waveform display.

(2) Cooling system: cycle refrigeration filtration system

(3) Supply system: sampling → analysis → supply, electrolyte analysis supply system.

2. Process advantages:

(1) The operation process is simple and the surface pretreatment process is simple and convenient.

(2) According to different performance requirements, the treatment time is 10-60 minutes.

(3) The solution is weakly alkaline, pH 11-12, no heavy metal, environmental protection oxidation technology, strong oxidation cation.

(4) It has a wide range of applications.

3. Full function:

According to different surface accuracy and wear resistance requirements, it can have the following functions:

(1) Micro arc oxidation( 2) Hard oxidation( 3) Anodic oxidation.

4. Excellent performance:

According to the requirements, the following film types can be processed:

(1) Wear resistant( 2) Corrosion resistant( 3) High temperature resistance( 4) Insulation( 5) Optics( 6) Functional and composite functional coatings.

5、 Application of micro arc oxidation

The application of micro arc oxidation technology represents the forefront of the application and development of a new generation of environmental protection oxidation technology. Plasma ceramic oxidation coating is widely used in construction, aviation, aerospace, textile, shipbuilding, electronics, automobile manufacturing, weapon industry, nuclear industry and other fields due to its excellent properties of wear resistance, corrosion resistance, high temperature resistance and insulation.

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