Q: What are the advantages of plasma spray coating?
A: The principle of the plasma spraying process is to change the surface properties of the material, use a certain heat source to heat the sprayed material to a molten or semi-melted state, blow it into tiny particles, and spray it onto the surface of the base material through island velocity airflow to form a various coating processing methods. Plasma spraying not only has the same size as other spraying methods, but also has the advantages of unlimited part size, wide base material, small processing edge, and spray strengthening of the surface of ordinary base parts.
1.The substrate is not heated, the parts are not deformed, and the heat treatment state is not changed.
Since the parts are not charged during spraying and the base metal does not melt, although the temperature of the plasma flame is high, the energy is very concentrated. The axial temperature gradient of the plasma arc is very large. Generally, the temperature rising of the parts does not exceed 200 ℃, so the parts will not deform, which is very beneficial for the repair of thin-walled parts, slender rods and some precision parts. Since the heat treatment properties of the base metal will not change below 200°C, some high-strength steels can be sprayed.
2. There are a wide range of materials that can be sprayed, and there are many types of coatings.
Due to the high temperature of the plasma flame, various spraying materials can be heated to a molten state, so there are a wide range of materials available for plasma spraying, so that spray coatings with various properties can be obtained, such as wear-resistant coatings, thermal insulation coatings layer, high temperature oxidation resistant coating, insulating coating, etc. In terms of the wide range of coatings, oxygen-acetylene flame spraying, electric arc spraying, high frequency induction spraying and explosive spraying are not as good as plasma spraying.
3. The process is stable and the coating quality is high.
Each process parameter of plasma spraying can be controlled quantitatively, the process is stable, and the coating reproducibility is good. In plasma spraying, the flying speed of particles in the molten state can reach 180-480m/s or even higher, which is much higher than the particle flying speed of oxygen-acetylene flame powder spraying of 45-120m/s. The molten particles are fully deformed when they collide with the parts. The coating is dense, and the bonding strength with the substrate is high. The normal bonding strength of the plasma sprayed layer on the base metal is usually 30 to 70 MPa, while the oxygen-acetylene flame spraying is generally 5 to 20 MPa. Since the atmosphere can be controlled by changing the gas during plasma spraying, the oxygen or nitrogen content in the coating can be greatly reduced.