What are the characteristics and disadvantages of supersonic flame spraying

       Supersonic flame spraying is a thermal spraying process that has developed rapidly in the world in recent years. Its unique features are:



    1) The flame speed is fast, which can reach 1770m/s, which is 5 to 10 times faster than the flame speed of other thermal spraying processes.

    2) The coating density is high, which can reach 98%~99%, while other thermal spraying processes can only reach 85%~95%. Due to the high-speed flight of the particles, the bonding mechanism of the coating is more focused on mechanical anchoring, so the bonding strength with the substrate is high, which can reach 60MPa~80MPa.

    3) The flame temperature is moderate, and the coating maintains the original physical and chemical properties of the material when spraying carbide ceramics. Compared with other spraying processes, the coating hardness of the same material is higher.

    4) It can be sprayed with strong wear resistance, medium and high temperature resistance, and erosion resistance coating, and the spraying cost is high.

    Excessive flame flow rates also impose certain limitations on the materials that can be sprayed. The temperature of the supersonic flame is generally less than 3000°C. The powder stays in the flame for a very short time, and the powder is not heated enough to melt high melting point materials. Therefore, it is difficult for supersonic flame spraying to spray alumina, chromium oxide, zirconia, molybdenum, tungsten, etc. High melting point materials; exothermic materials such as nickel-clad aluminum are also too fast to release heat and cannot exert the effect of secondary heating. Due to the short heating time, supersonic flame spraying also limits the particle size range of the powder, and the powder with large particles is easily bounced back due to insufficient melting, resulting in a decrease in deposition efficiency and an increase in process cost.