Introduction to the basic principle and coating structure of metal thermal spraying

       Metal thermal spraying technology is one of the main technologies for modern metal surface treatment. It has flexible process, few operation procedures, fast repair, and is not affected by the site and the size of the workpiece. It is widely used in major machinery and other industries. The basic process of spraying is as follows:



1. The spray material is heated to a molten or semi-melted state;



2. The droplets of the spray material are atomized;



3. Atomized or softened fine particles fly;

4. The tiny particles hit the surface of the substrate and form a coating.

The thermal spray coating is formed by the lateral flow of particles, flattening, rapid solidification and cooling, and continuous accumulation. Since the thermal spray coating is a typical layered structure, the performance of the coating is mostly directional. Appropriate treatment and remelting of the coating can both transform the layered structure into a homogeneous one and eliminate oxide inclusions and pores in the layered structure.



The bonding of the coating includes the bonding of the coating to the substrate surface and the cohesive bonding of the coating. There are three general ways of combining:



1. Mechanical bonding: When the molten particles hit the surface of the substrate and rapidly cool and solidify, they will bite the uneven substrate part due to shrinkage to form a mechanical bond.



2. Physical bonding: the bonding method that attaches to the surface of the substrate by means of the spray layer between the molecules.



3. Metallurgical bonding: When the molten fine particles hit the surface of the substrate at high speed, the interface between the coating and the substrate appears to diffuse and alloy.