Characteristics of thermal spraying technology and knowledge sharing of coating function classification

       Thermal spraying technology has a long history, and its origin can be traced back to the beginning of this century. Earlier people just used molten metal to compress to form a liquid stream, and then sprayed the surface of the object to be sprayed to form a film-like structure. Among them, the core technical difficulties are mainly the spraying temperature, the droplet and the impact speed on the surface of the sprayed object. Throughout the history of the development of thermal spraying technology, it is based on these three points to move forward.

  The temperature and speed depend on different heat sources and equipment structures. In a sense, the higher the temperature and the greater the speed, the more conducive to the formation of an excellent coating. This has led to the competition and coordination of the two elements of temperature and speed in the entire technological development process. The choice of a wide range of spraying materials is another advantage of thermal spraying technology, which can make the work surface of different equipment be "pointed into gold, wearing helmets and armor". It is these three elements, as well as many other controllable factors, that make thermal spraying a truly unique technology with superimposing effects. It can design a variety of modified surfaces required to obtain maintenance from general machinery. , Until it is widely used in high-tech fields such as aerospace and biological engineering.

One. Spraying materials

  Spraying materials have different forms such as powder, wire, ribbon and rod, and their components are metals, alloys, ceramics, cermets and plastics. Powder materials occupy an important position, with more than one hundred types. Wires and strips are mostly metals or alloys (composite wires still contain ceramics or plastics); there are only a dozen kinds of rods, most of which are oxide ceramics.

Two, spraying method

  To provide different heat sources, it can be divided into combustion method and electric heating method. The former includes combustion flame spraying, explosive spraying and high velocity flame spraying (HVOF); the latter includes arc spraying and plasma spraying (subdivided into atmospheric plasma spraying, low pressure plasma spraying and water stabilized plasma spraying). The spraying process has an important impact on the coating is the spraying temperature (strictly speaking, the temperature when the droplet impacts the surface of the substrate) and the speed at which the droplet impacts the surface of the substrate.

Three. Characteristics of thermal spraying technology

  1. The base material is not limited, it can be metal or non-metal, and can be sprayed on various base materials;

  2. The sprayable coating materials are extremely wide. Thermal spraying technology can be used to spray almost all solid engineering materials, such as cemented carbide, ceramics, metals, graphite, etc.;

  3. The temperature rise of the base material is small during the spraying process, and there is no stress and deformation;

  4. The operation process is flexible and convenient, not limited by the shape of the workpiece, and the construction is convenient;

  5. The thickness of the coating can be from 0.01 to several millimeters;

  6. There are various coating properties, which can form coatings with various special functions such as wear resistance, corrosion resistance, heat insulation, oxidation resistance, insulation, conductivity, and radiation protection;

  7. The advantages of strong adaptability and good economic benefits.