The difference between thermal spraying and spray welding
1, The coating with different bonding mechanism
The coating of thermal spray bonding mechanism is mechanical bond, metallurgical-chemical bond and physical bond. Which mainly based on mechanical bond. And the spray welding bonding mechanism is chemical metallurgical bond. Achieving a permanent connection between atoms.
2, The heating condition of work-piece is different
Spraying without re-melting process, the work-piece surface temperature can always be controlled below 250 degree. Normally no deformation occurs and the micro-structure of the work-piece changes. The spray welding should melt the coating, and the remelting temperature can reach more than 900 degree. It is not only easy to cause deformation of the work-piece, but most of the work-pieces will be annealed or incompletely annealed.
3, The bonding state with the substrate is different
The combination of the spray coating and the surface of the substrate is dominated by mechanical occlusion. Despite the existence of micro-area metallurgical bonding, the bonding strength of the coating is not high, typically 30 to 50 MPa. Spray welding forms a metallurgical bond with the surface of the substrate through the melting of the coating, and the bond strength is generally 343-440 MPa.
4, The spray materials is different
Spray welding requires self-fluxing alloy powders, and spraying is few requires for self-fluxing alloy powders, even spray can use the alloy powders without self-fluxing property. 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 but not for the spray welding process. The powder used for powder flame spraying must be a self-fluxing alloy powder, and the powder used for spraying is not limited.
5, Different cover structure
The spray welding coating is uniform and dense, and it is generally considered that there is no porosity, and the spray coating has pores.
6, Different carrying capacity
The spray coating cannot withstand impact loads and high contact stress, and it is suitable for spraying on the surface of various surface-contacting work-pieces. The spray welding coating can withstand impact loads and high contact stress, and it can be used in wire contact applications.
In summary, when the work-piece load is large, especially when it is subjected to impact load and used in corrosive media, it is advisable to adopt spray welding. When the work-piece does not allow deformation, or it is not allowed to change its original structure, and the work-piece does not suffer, or when only lightly impact loads are applied, spraying is preferred.
