Plasma spraying uses a plasma source as a heat source, and a thermal spraying method based on spraying powder materials. The plasma arc is a special structure of a spray gun (called a plasma spray gun) between the cathode and the water-cooled nozzle. The gas is ionized to form an arc, and the arc is passed through a nozzle hole having a small aperture. Due to the diameter limitation of the arc column, the strong column is forcibly compressed. In addition to mechanical compression, the arc is also subjected to thermal compression and self-magnetic compression. The arc energy is highly concentrated, and the energy density of the cross section can reach 10^5-10^6W/cm^2. The center temperature can be raised to 15000-34000 K, becoming a high-energy dense beam heat source. In this case, the gas in the arc column becomes a plasma as the degree of ionization increases. This type of compression type arc is called a plasma arc, abbreviated as a plasma arc. Compared with free arc, the difference between plasma arc and free arc is that the column is fine, the current density is high, the gas ionization is sufficient, the energy is concentrated, the temperature is high, and the high melting point and high hardness materials can be melted. The materials that can be sprayed are extremely wide, and the powder is sprayed. The heated temperature is high, and the obtained kinetic energy is large (the particles can be accelerated to subsonic or even supersonic speed), and the resulting coating has high density and good bonding strength.