Date Published:May. 10. 2016
Surface Treatment
| Method |
Principles and features |
Materials |
Nature |
|---|---|---|---|
| Electroplating |
Soak the material into the plating bath as an negative electrode to perform electrolytic deposition of metal film on the material surface by direct current. |
The materials are metal and plastic (electroplating by conducting with electroless plating on the surface). |
For decoration, 1μm or below, for protection and industrial use, 1 - dozens μm or above. IN many cases, pin holes are left. |
| Hot-dip plating |
Soak the material into dissolved metal and then pull it up for consolidation and coating of the dissolved metal. |
Primary materials are iron and steel and coating metal includes Al, Zn, Sn and Pb, etc. |
Thick coating is possible. Adhesion and deforming processing property depend on the nature of alloy layer formed between the coating layer and the material. |
| Diffusion plating |
Metal elements are diffused and cemented over the material surface layer. As the processing temperature is high (around 1000°C), post heat treatment is required. |
Primary materials include iron and steel, Fe-base and Ni-base heat-resistant alloy, etc. Coating metal includes Al, Cr and Si, etc. |
Alloy layer thickness is tens - hundreds μm. |
| Evaporation coating |
Physical evaporation method: Coating by vacuum evaporation, spattering and ion plating, etc. Chemical evaporation method: Coating by decomposition of gas compound. |
Materials include metal, ceramic and plastic. Coating materials are metal and ceramic. |
Generally, the evaporation speed is low for the physical evaporation method. The chemical evaporation method cannot avoid high temperature processing. |
| Thermal spraying |
Power or particles of thermal spraying materials heated to the dissolved state are sprayed onto the material surface to form coating. The material temperature during spraying is below 200°C. |
Materials include metal, ceramic and plastic, etc. Thermal spraying materials are metal, ceramic, plastic or their mixture. |
The adhesion strength is relatively low. The film has air holes. The practical film thickness is about 0.6 mm or below. |
| Flitch |
Rolled pressure welding method and explosion welding method, etc. Processing objects are simple shapes such as plates and cylinder inner face, etc. |
Materials are metal and mostly iron and steel. Flitch materials are metal and alloy. |
For explosion welding, the flitch material thickness is about 3 mm or below. |
| Anode oxidation |
Materials are electrolyzed in electrolysis solution such as sulfuric acid and oxalic acid as an anode to form an oxide film on the material surface. |
Primary materials are Al and Al alloy. Others include Mg, etc. |
An oxide film consists of a dense layer and porous layer. Apply normal sealing processing. Good adhesion. Coloration possible. |
| Chemical conversion coating |
Form a phosphate or chromate film on the material surface by soaking or spraying method. |
Materials include iron and steel, Al and Zn, etc. |
Primarily, a phosphate film applies to iron and steel materials and a chromate film to Al. |
| Carburizing |
Carbon elements are diffused and cemented over the material surface layer. Processing temperature is 850 - 950°C. Apply quenching after the processing. |
The material is steel with C content of 0.2% or below (steels for case hardening). |
The carbonizing is 0.5 - 5mm and the hardness is 700 - 850HV. Pay attention to the material deformation caused by the processing and quenching after the processing. |
| Nitriding |
Nitride elements are diffused and cemented over the material surface layer. Processing temperature is 475 - 580℃. Heat treatment and machine processing are possible before the processing. |
Materials are nitrided steel for gas nitriding (containing Cr, Mo and Al, etc.). Most steel types for ion nitriding. | The nitriding depth is 0.9mm or below. Hardness is 600 - 1150HV. Material deformation is small. |
| Nitrocarburizing |
Perform nitriding at the same time with carbonizing. Processing temperature is 700 - 900℃. Apply quenching after the processing. |
Materials are the same as those for carbonizing. The same can apply to carbon steel. |
Nitrocarburizing depth is 1mm or below. Hardness is about 800HV. |
| Sulfurizing |
Sulfur elements are diffused and cemented over the material surface layer. Processing temperature is 400 - 600℃. |
Any steel material and steel type can be used. |
Friction coefficient decreases from the ferric sulfide film thickness 0.2μm. |
| Nitrosulphurizing |
Perform nitriding at the same time with sulfurizing. Processing temperature is 560 - 570℃. |
Materials are the same as those for nitriding. |
The nitrosulphurizing depth is 0.1 - 0.5mm. |
| Induction quenching |
Perform quenching after rapid heating and rapid cooling by high frequency conductive current on the material surface. |
Materials are iron and steel. Especially, medium carbon steel, alloy steel and cast iron, etc. |
Hardened layer thickness is 0.4 - 5mm. Working time is short. Material deformation is small. |
| Flame hardening |
Perform quenching after rapid heating and rapid cooling by oxygen-fuel flame on the material surface. |
The same as above |
Hardened layer thickness is 1 - several mm. |
| Other surface quenching |
Perform quenching after rapid heating and rapid cooling by laser beam and electric beam, etc. |
Any materials can be used as long as they have a quenching property. |
The hardened layer is extremely thin. Local hardening is possible. |
| Plastic lining |
Coat the material surface by the sheet lining method, thermal spraying method or application method, etc. |
The coating materials are polyethylene, vinyl chloride, fluorine resin and rubber, etc. |
Thick coating is possible. It may be 1mm or above in some cases. |
| Ceramic coating |
Coat the material surface by the evaporation method, thermal spraying method or quenching method, etc. |
Coating material is glassy ceramic (enamel). Various ceramic. |
Less adhesive. Repeated heating and cooling may cause cracks on the film. |
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