Combination form of spray coating

       During the formation of the spray coating, the actual bonding point of each particle does not fill the entire contact surface of the particle. At the same time, the temperature and heat distribution of the central and edge regions of the flame are very uneven, resulting in different heating conditions of each particle. In addition, it is impossible for each particle to have the same thermal and mechanical state, so the particle junction cannot be Pores or porosity are avoided, which will inevitably affect the bonding properties of the coating. If the sandblasting machine is coupled with the influence of the thermal stress formed by the spraying process, the bonding ability of the sprayed layer has a certain limit.



Based on the previous analysis, the combination forms of the spray coating of the automatic sandblasting machine can be summarized into the following four types:



1. Mechanical combination



This is the main form, that is, the molten or nearly molten particles are deformed, embedded, occluded and packed under the impact of jetting, and finally condense and shrink, and are bonded to the surface of the substrate.



2. Weak non-valent interaction force (Vander Waals force)



That is, on a clean surface, the atomic distance between the particles and the substrate at the point of contact reaches the force generated by the atomic and molecular distances.



3. Chemical bonding



That is, when the distance between the atoms on the contact surface reaches the value of the atomic lattice constant, the activation energy of the atoms exceeds the bond energy, forming a chemical bond between the atoms of the coating and the atoms of the substrate.



4. Micro-diffusion bonding



That is, the mutual diffusion between the elements in the sprayed particles and the elements in the substrate under certain conditions, and sometimes even a bonding layer is formed by these diffusing elements.



We usually refer to the first of the above four bonding forms as mechanical bonding, which is the main form of spray coating bonding. The last three bonding forms are called metallurgical bonding. In general, the last three combination forms of the domestic sandblasting machine are weak, and it is the secondary form of the combination of the spray coating.