Metal spraying

In the spraying process, a stream of finely dispersed molten or heated to boiling particles is directed onto the metal surface. When interacting with the surface, the sprayed elements are deposited on the surface of the workpiece, ensuring reliable, non-destructive contact.

In general, there are two basic types of spraying: gas dynamic spraying and vacuum spraying. In vacuum spraying, the transfer of sputtered particles is carried out at a vacuum of 10-2 Pa, which contributes to a tighter adhesion of the sputtered layer and is carried out in magnetron, cathode or ion-plasma installations. In these units a stream of molten fine particles is fed to the treated surface, since it was believed to be a prerequisite for creating a stable, low-porosity and homogeneous layer.

The gas-dynamic spraying technology involves feeding fine metal particles (0.01-50 microns) through a supersonic nozzle (600-700 m/s) and heating compressed air to 400-600°C. As a result, a layer of metal is formed that has high adhesion (40-100 N/mm2) and low porosity (1-3%).

Metal spraying is one of the most modern and promising technologies of body repair. Spraying solves the problem of restoring worn surfaces, body geometry, repair of light-alloy parts and mechanisms (elimination of cracks, chips). In addition, zinc sputtering or galvanizing is the best protection for metal and welding joints from corrosion.

If even without heating the particles to the melting point and directing the flow onto the surface to be heated with supersonic speed of 600-700 m/s (sound speed is 331 m/s), the indices of the coating obtained: tensile strength, microhardness, porosity and homogeneity were not inferior to those of coating obtained by high-temperature spraying. The point is that when heated, the air pressure in the chamber increases in accordance with Charle's law and, consequently, the rate of flow from the nozzle also increases. The metal particles that have gained a huge speed in the gas jet are softened and welded to the substrate upon impact with the substrate.

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