How much do you know about micro-arc oxidation?

Process introduction

The full English name of micro-arc oxidation is Microarc oxidation, abbreviated as MAO, and its other name is micro-plasma oxidation, the full English name is Microplasma oxidation, abbreviated as MPO. Through the combination of electrolyte and corresponding electrical parameters, on the surface of aluminum, magnesium, titanium and their alloys, a ceramic film layer mainly composed of base metal oxides is grown on the surface of aluminum, magnesium, titanium and their alloys by the instantaneous high temperature and high pressure generated by arc discharge.

Take the micro-arc plasma oxidation of aluminum and its alloys as an example, that is, aluminum and its alloys are placed in an electrolyte solution, and through high-voltage discharge, spark discharge spots are generated in the micropores of the material. Under the combined action of, a hard ceramic layer mainly containing α-Al203 and containing r-Al203 is formed on its surface. The basic principle of micro-arc oxidation technology is similar to that of anodizing technology, the difference is that plasma discharge is used to enhance the chemical reaction that occurs on the anode. Micro-arc oxidation is in the spark discharge zone, and the voltage is relatively high. When the anodic oxidation voltage exceeds a certain value, the initially formed oxide film with a certain degree of insulation is broken down, resulting in micro-arc discharge, forming an instantaneous ultra-high temperature area ( (Up to 8000 degrees Celsius), the oxide or base metal is melted or even vaporized in this area. In the contact reaction with the electrolyte, the melt is chilled to form a non-metallic ceramic layer; the film is uniform and dense, with relatively pores The area is small, and the overall performance of the film is greatly improved. Because the ability of the film to be broken down under the action of a high-voltage electric field is enhanced, the diffusion ability of positive and negative ions in the film is enhanced. Micro-arc oxidation can obtain a thicker film than anodic oxidation. Layer; And on the surface of some aluminum alloys with a large proportion of Cu, Si and other elements that are not easy to form anodized, thick films with good performance can also be obtained. Since the micro-arc oxidation ceramic is a dense ceramic layer grown directly on the metal surface in situ, it can improve the material's own corrosion resistance, wear resistance, electrical insulation and high temperature impact resistance.

The basic process is:

Degreasing—water washing—micro-arc oxidation—pure water washing—closed—drying

2. Bath/Equipment

The composition of the micro-arc oxidation solution is relatively simple. At present, most bath solutions are mainly weakly alkaline aqueous solutions. Sodium silicate, sodium aluminate or sodium phosphate and other ingredients are often added to the actual bath liquid. In order to obtain various colors of micro-arc oxide film, different metal salts can be added, and the corresponding color can be obtained by doping in the micro-arc oxide film by deposition and doping of different metal ions, such as Na2WO4, NH4VO3, etc.

Process example:

Electrolyte composition: K2SiO3 5~10g/L, Na2O2 4~6g/L, NaF 0.5~1g/L, CH3COONa 2~3g/L, Na3VO4 1~3g/L; solution pH is 11~13; temperature is 20~ 50℃; the cathode material is stainless steel plate; the electrolysis method is to rapidly increase the voltage to 300V and hold for 5-10s, then increase the anodizing voltage to 450V, and electrolyze for 5-10min.

3. Process application

The micro-arc oxide film layer has wear resistance, corrosion resistance, high hardness, low wear and heat resistance. It is generally used in automobiles, aerospace, ships, weapons and other industries, such as automotive motors, pistons, bearings and other aluminum alloys. Surface treatment is to use the high hardness and low wear characteristics of the micro-arc oxidation film. There are also ship impellers, connecting fittings, pipe fittings, etc., which take advantage of its corrosion resistance characteristics.

Process characteristics

1. The surface hardness of the material is greatly improved. The microhardness is 1000 to 2000HV, up to 3000HV, which is comparable to cemented carbide and greatly exceeds the heat treatment of high-carbon steel, high-alloy steel and high-speed tool steel. Hardness

2. Good wear resistance;

3. Good heat resistance and corrosion resistance. This fundamentally overcomes the shortcomings of aluminum, magnesium, and titanium alloy materials in the application, so the technology has broad application prospects;

4. It has good insulation performance, and the insulation resistance can reach 100MΩ.

5. The solution is environmentally friendly and meets environmental protection emission requirements.

6. The process is stable and reliable, and the equipment is simple.

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

8. The ceramic membrane is grown in situ on the substrate, the bonding is firm, and the ceramic membrane is dense and uniform.

Media Contact:

ShenZhen Ai Produce Technology Information Co.,Ltd

East of Shenzhen,Guangdong, China.

Whatsapp: 86-189 0243 7930


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