What is the difference between thermal spraying and spray welding of wire drawing machine towers?

       1. Coating bonding mechanism is different



The bonding mechanism of thermal spraying is: mechanical bonding, metallurgical-chemical bonding, and physical bonding. Among them, the mechanical combination is the main one. The bonding mechanism of spray welding is: chemical metallurgical bonding to achieve permanent connection between atoms.



2. The heating conditions of the workpiece are different



There is no remelting process for spraying, and the surface temperature of the workpiece can always be controlled below 250 °C. Generally, it does not produce deformation and changes the organizational state of the workpiece. However, spray welding needs to melt the coating, and the remelting temperature can reach more than 900 ℃, which not only easily causes deformation of the workpiece, but also annealing or incomplete annealing of most workpieces.



3. The bonding state with the substrate is different



The bonding between the spray coating and the surface of the substrate is mainly mechanical occlusion. Although there is micro-regional metallurgical bonding, the bonding strength of the coating is not high, generally 30-50 MPa. Spray welding forms a metallurgical bond with the surface of the substrate through the melting of the coating, and the bond strength can generally reach 343~440MPa.



4. Different spraying materials



Spray welding requires the use of self-fluxing alloy powder, while spraying does not require high self-fluxing properties of the powder, and it is not necessarily a self-fluxing alloy powder. Various self-fluxing alloy powders can be used for both spray welding and spraying. However, the spray powder does not have self-fluxing properties and can only be used for spraying and not for spray welding.



The powder used for powder flame spray welding must be self-fluxing alloy powder, and the powder used for spraying is not limited.



5. The structure of the covering layer is different



The spray welding layer is uniform and dense, and is generally considered to have no pores, while the spray coating has pores.



6. Different carrying capacity



The spray coating cannot withstand impact load and high contact stress, and is suitable for surface spraying of various surfaces contacting workpieces. The spray welding layer can withstand impact load and high contact stress, and can be used in line contact occasions.



In summary, when the workpiece has a large load, especially when it is subjected to impact loads and used in corrosive media, it is appropriate to use spray welding. When the workpiece is not allowed to deform or change its original structure, and the workpiece does not withstand Or when only bearing a slight shock load, spraying should be used.

At present, two processes are widely used: powder flame spray welding and plasma arc spray welding.