The main role of thermal spray preheating

       Preheating is the last step in the surface pretreatment process. It is generally carried out before spraying, so that the surface of the workpiece can obtain a fresh substrate surface with a certain temperature, which is very beneficial to improve the bonding strength between the coating and the substrate.



The main functions of preheating are as follows:



1) Remove moisture and condensate (such as water vapor, etc.) from the surface of the workpiece.



2) Increase the temperature of the substrate and reduce the temperature difference between the coating and the substrate, thereby reducing the difference in thermal expansion and contraction between the two, thereby reducing thermal stress and effectively preventing the coating from peeling or cracking.



3) It is beneficial to the "thermal activation" of the surface, which can increase the contact temperature between the sprayed particles and the substrate, which is beneficial to promoting the physical and chemical interaction between the substrate surface and the coating, and at the same time, it can improve the powder deposition rate.



4) The cooling rate of the sprayed particles can be reduced, which is not only beneficial to the deformation of the sprayed particles, but also reduces the shrinkage stress of the particles, thereby reducing the stress accumulation of the coating.



The above effects are all beneficial to improve the bonding strength between the coating and the substrate. Practice has proved that proper preheating treatment is not only beneficial to improve the bonding strength, but also can significantly improve the working life of the coating.