Gear surface treatment: common methods and characteristics
Gear surface treatment is a key process to improve gear performance.
●Enhance corrosion resistance
●Wear resistance
●Surface finish and appearance
●Improve fatigue strength.
Electrogalvanizing
This is a typical anti-rust electroplating method. After chromate treatment, the appearance quality of the gear can also be improved, and the coating thickness is generally between 2-25 microns. There are three common types of treatment:
●Monochromate
It is silvery white with a slight bluish tint. Its anti-rust performance is not as good as electrogalvanizing, but the price is lower.
●Chromate
It has a colorful appearance, including red, yellow and green, and its corrosion resistance is worse than monochromate.
●Black chromate
It is basically black, but it may be slightly red depending on the shape of the product. Among the three electrogalvanizing methods, black chromate has the best corrosion resistance.
Chemical nickel plating
This is a plating method that does not require electroplating. It has corrosion and wear resistance, and is suitable for products that require uniform coating thickness (3-10 μm), complex shapes or high precision requirements.
Black Oxidation Treatment
This is an alkaline black oxidation treatment. The material is treated in a strong alkaline solution heated to 140°C, and the steel undergoes a chemical reaction to turn black, which acts as a rust-proof treatment. A film of ferroferric oxide less than 3 μm thick is formed on the surface.
Raydent Treatment
This is a registered brand of Raydent Industries, Ltd. It has excellent rust-proof properties and a black surface. Similar to electroplating, it forms a 1-2 μm thick Raydent film on the surface, which is very strong and does not fall off easily.
Phosphate Treatment
Iron phosphate type: It forms a thin amorphous film and is used as a primer for painting interior products.
●PALFOS M
This is a manganese phosphate treatment with a coating thickness of about 3-15 μm. It can be used as a rust-proof film and is also suitable for sliding parts due to its wear resistance.
Solid Lubrication Treatment
This is a dry coating spray that is very useful in situations where direct lubrication is not possible. By spraying onto the tooth surface, the lubricant adheres and dries.
WPC treatment
The WPC process is a surface treatment technology that can effectively enhance the fatigue resistance of metals and reduce their friction coefficient. The thickness of the WPC coating is extremely thin, usually between 40 and 200 microns, and the speed during spraying is not less than 100 meters per second. During the spraying process, the coating releases heat instantly, causing the metal crystals to melt, and then forms a dense coating through rapid cooling. Generally speaking, after this treatment, the size of the coating changes very little, usually controlled within the range of 1 to 2 microns.
Related Articles – Improving Gear Performance: A Guide to Surface Treatment Technologies
Gears are critical components in mechanical systems, and their performance is greatly affected by the condition of their surfaces. Surface treatment processes can be tailored to specific operational needs, from rust prevention to improved wear resistance. Here is an overview of key technologies and their unique advantages.
Galvanizing is the preferred solution for rust prevention of steel. This electroplating method deposits a coating of 2-25 microns and can be optionally chromated to enhance protection and aesthetics. Among them, black chromate has top corrosion resistance and presents a nearly black appearance (may have a slight red tint due to the shape of the product); colored chromates (composed of red, yellow, and green) have the second best protection effect; while monochromates have weaker rust protection ability, but the shape cost is silvery white with a light blue tint.
For scenes where complex shapes or high-precision parts require uniform electroplating, chemical nickel plating is the ideal choice. This electroless process forms a 3-10 μm film with excellent corrosion and wear resistance, making it a favorite for complex gear designs.
The black oxide treatment relies on a chemical reaction in an alkaline solution at 140°C to form a ferroferric oxide layer (less than 3 μm) on the steel surface. This is a cost-effective method to achieve rust protection with minimal impact on part dimensions.
The Raydent treatment is a proprietary process that provides excellent rust protection with a 1-2 μm black film. The layer is tightly bonded to the surface and does not easily flake off, and its simplicity of application is comparable to traditional electroplating methods.
Phosphate treatments are available to meet various needs: Iron phosphate forms an amorphous film that is ideal as a substrate for coating internal gears; PALFOS M is a manganese phosphate variant that forms a coating with a thickness of 3-15 μm, combining rust and wear resistance for sliding gear components.
Solid lubrication treatments are used when direct lubrication is not possible. The dry spray is applied to the gear teeth and dries to form a molybdenum disulfide-rich coating that reduces friction and corrosion while ensuring smooth operation.
The WPC treatment focuses on improving fatigue strength. By spraying fine particles at speeds in excess of 100 m/s, the WPC treatment melts and rapidly cools the metal surface to form an ultra-thin coating (40-200 μm). With dimensional changes of less than 2 μm, the treatment is ideal for improving durability while maintaining accuracy.
Each treatment targets specific gear challenges, from corrosion to fatigue. Selecting the right gear depends on operating conditions, part design, and performance goals, ensuring the gear will perform reliably under the expected loads.