The process flow of the coating spraying production line for automotive engine bearing shells usually includes pretreatment, spraying, and post-treatment and other main links. The specific introduction is as follows:

1. Workpiece preparation

• Bearing shell cleaning: Put the bearing shells into special cleaning equipment and use organic solvents, alkaline solutions or ultrasonic cleaning and other methods to remove oil stains, impurities and machining residues on the surface of the bearing shells to ensure the surface is clean.

• Degreasing treatment: Further use chemical degreasers to treat the bearing shells to completely remove the grease on the surface so as to improve the adhesion of the subsequent coating.

• Rust removal treatment: For the bearing shells that may have rust, use pickling, shot blasting or sandblasting and other methods for rust removal to make the surface of the bearing shells reach the required roughness and cleanliness.

2. Preheating

• Put the cleaned bearing shells into the preheating furnace and heat them to a certain temperature, generally between 100 °C and 200 °C. The purpose of preheating is to remove the moisture on the surface of the bearing shells, improve the bonding force between the coating and the bearing shells, and enable the bearing shells to better absorb the coating material during the spraying process.

3. Spraying the primer layer

• Selecting the primer layer material: According to the usage requirements of the bearing shells and the coating design, select appropriate primer layer materials, such as nickel, chromium, molybdenum and other metal or alloy powders.

• Adjusting spraying parameters: Including spraying distance, gun moving speed, powder feeding speed, gas pressure, etc. Generally, the spraying distance is between 150 mm and 300 mm, and the gun moving speed is between 500 mm/s and 1500 mm/s.

• Performing primer layer spraying: Use plasma spraying, flame spraying or arc spraying and other methods to spray a uniform primer layer on the surface of the preheated bearing shells. The thickness of the primer layer is usually between 0.1 mm and 0.3 mm.

4. Spraying the working layer

• Selecting the working layer material: Common working layer materials include polymer coatings, cermet coatings, etc. For example, polymer coatings such as polytetrafluoroethylene (PTFE) have good self-lubricating properties and a low coefficient of friction.

• Precisely adjusting parameters: According to the characteristics of the working layer material and the coating requirements, adjust the spraying parameters again. For example, for the PTFE coating, the spraying temperature is generally controlled between 250 °C and 350 °C.

• Spraying the working layer: Use the same or different spraying methods as for the primer layer to spray the working layer on the primer layer. The thickness of the working layer is generally between 0.2 mm and 0.5 mm.

5. Cooling

• Natural cooling: After the spraying is completed, let the bearing shells cool naturally in the air to room temperature. The cooling speed should not be too fast to avoid internal stress that may cause the coating to crack or fall off.

• Forced cooling: For some coatings with strict requirements for the cooling speed, forced cooling methods such as air cooling or water cooling can be adopted, but the cooling rate and temperature gradient need to be controlled.

6. Post-treatment

• Grinding processing: Use grinding or polishing and other methods to grind the surface of the bearing shell coating to achieve the required surface roughness and dimensional accuracy. Generally, the surface roughness Ra value is controlled between 0.1 μm and 0.8 μm.

• Quality inspection: Use a variety of inspection methods to comprehensively inspect the quality of the bearing shell coating. For example, use a microscope to observe the microstructure and thickness uniformity of the coating, use a hardness meter to measure the hardness of the coating, and use a friction tester to test the friction coefficient and wear resistance of the coating.

7. Packaging and warehousing

• Cleaning and packaging: Clean the inspected qualified bearing shells to remove dust and debris on the surface, and then use special packaging materials for packaging to prevent damage during transportation and storage.

• Warehousing and storage: Put the packaged bearing shells into the warehouse for proper storage, and store them according to the specified storage conditions and management requirements, waiting for subsequent assembly and use.