The selection and design of the brush coating for diesel engine are as follows:
The selection and design of the brush plating of the diesel engine includes the transition coating and the working coating. The transition coating should be located between the base metal and the working coating. It is directly coated on the base metal after the activation treatment. It is a coating with specific performance and special function. It is called the over plating coating. Also called the bottom coating. In the brush plating process, the plating process is also called the plating process. The purpose of the transition layer is to:
It is difficult to brush plating directly on some matrix metals. It is difficult (poor bonding with the matrix), and the transition layer can be used. The plating coating can be brushed by using the "bilateral affinity" of the transition layer with the base metal and the working coating metal. For example, in the aluminum silicon alloy. Fast nickel plating and low bonding strength. If aluminum and silicon alloy is first coated with a thin layer of special nickel as the bottom layer, then then fast nickel plating on special nickel will achieve good results.
2. Improve the stability of the working coating. Some coatings are plated directly to the matrix metal, although it has good bonding strength, but because of diffusion, electrical corrosion and other reasons, the working ability of the coating decreases. For example, the electroplating of copper directly on aluminum or steel will produce electrochemical corrosion. If a special nickel is plated on the aluminum parts as a transition layer in advance, Brush plating copper can avoid the electrochemical corrosion of parts.
The working coating is located at the top of the working surface of the plating part, directly bearing the working load and friction. The working layer should have good bonding performance to the matrix metal or the transition layer metal; the working coating itself has good performance to meet the requirements of the working condition and use; the deposition rate of the plating bath is fast under the premise of meeting the above two requirements. The rate is high and the economy is.
In the design of the coating, attention should be paid to controlling the thickness of the same continuous brush plating for the same coating. As the thickness of the coating increases, the residual strength in the coating increases and the thickness of the same coating may cause a crack or stripping of the coating. For this reason, the coating has a safe thickness, that is, the best coating allowed by the same continuous brush plating coating. Large thickness value.
When a coating with large thickness is needed, a layered brush plating method can be used, that is, after one of the brush plating is reached to a certain thickness, the coating is replaced by another coating thickening, and the thickness of the coating is increased by alternately brush plating until the required thickness is reached. This coating is composed of 2 or more kinds of properties in accordance with certain requirements. The composite coating is called the composite coating. When the coating requires a large thickness, the composite coating can improve the productivity, improve the performance of the thick coating, save the precious metal and improve the economy. However, the most outer layer of the composite coating must be the selected working coating. The composite coating is designed as a special nickel + fast. Nickel (O.l mm) + low stress nickel (0.05 mm) + fast nickel (0.1 mm) + low stress nickel (0.05 mm) + fast nickel.
