Thermal Spray Welding Technology

Thermal spray welding technology

(1) Principle and characteristics of thermal spray welding technology is a surface metallurgical strengthening method by using a heat source to remelt or partially melt the coating material on the surface of the matrix and condense it on the surface of the matrix to form a surface layer with metallurgical combination with the matrix, also known as fusion. Compared with other surface treatment processes, the microstructure obtained by thermal spray welding is compact, with few metallurgical defects and high bond strength with the matrix, but the selection of materials is narrow, and the deformation of the substrate is much larger than that of thermal spray welding, and the composition of the thermal spray welding layer is different from the original composition. (2) Classification of thermal spray welding technology mainly includes flame spray welding, plasma spray welding, and so on. (1) Flame spray welding: firstly, the powder is sprayed on the surface of the matrix, and then the coating is heated directly by flame so that the coating is remelted on the surface of the matrix, and the surface of the matrix is completely wet, and the interface has mutual element diffusion, forming a solid metallurgical combination. Characteristics of flame spray welding: simple equipment; The process is simple; The bonding strength between coating and matrix is high; The corrosion resistance of the coating is good. (2) the plasma spray welding, plasma arc as heat source heating substrate, the surface of the molten pool, at the same time to into plasma arc spray welding powder materials, powder preheating in the arc column, a molten or semi-molten state, as the flow injection to the molten pool, after fully melted out of gas and molten slag, side by side spray gun after alloy molten pool solidification, spray welding layer can eventually form. Plasma spray welding features high production efficiency; Can spray welding refractory materials, low dilution rate, good process stability, easy to realize automation, spray welding layer smooth, uniform composition and organization, coating thickness is larger and the test process can be accurately controlled. (3) The difference between thermal spray welding technology and thermal spraying technology ① workpiece surface temperature: spraying workpiece surface temperature < 250℃; Spray welding should be > 900℃. (2) Binding state: the spraying layer is mainly combined with machinery; The spray welding layer is metallurgical. Powder material: spray welding with a self-melting alloy powder, spray powder is not limited. (4) Coating structure: the spraying layer has pores, and the spray welding layer is uniform and dense without pores. ⑤ Bearing capacity: spray welding layer can withstand impact load and high contact stress. ⑥ Dilution rate: the dilution rate of the spray welding layer is about 5%~10%, and the dilution rate of the spray layer is almost zero.

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