The principle of supersonic arc spraying

The principle of arc spraying is a thermal spray coating process using two continuously fed wires as consumable electrodes to generate arc as heat source at its end, atomizing the molten wire with compressed air and spraying them to the working piece at a supersonic speed to form coatings with high bond strength, low porosity and low surface roughness. Supersonic arc spraying working principle is the same as ordinary arc spraying (subsonic atomization). It’s a continuously melting-atomization-deposition process. However, in the atomization mode, supersonic arc spraying is fundamentally different from ordinary arc spraying, which is that supersonic arc spraying uses supersonic atomization. It has many advantages. The atomization effect is good as the atomized particles are fine and uniform. The speed is high, which is favorable to obtain high-quality coatings. Ultrasonic arc spraying uses Laval nozzles to increase the velocity of the air stream from subsonic speed to supersonic speed, which enhances the acceleration effect of the airflow on the particles and therefore increases the particle speed.

The particle velocity has a great influence on the coating properties. With high particle velocity, the impact of the particle on the substrate will be strong and the particle deformation will be sufficient. It is beneficial to the combination of particles and matrix, particles and particles, so as to improve the bond strength and cohesive strength of the coating. With high particle velocity, the flight time in the air before particle deposition will be short and less oxide is generated during flight. It is beneficial to the combination of particles, thereby increasing the cohesive strength of the coating and reducing the porosity of the coating. The higher the particle speed is, the more favorable it is to obtain a high quality coating. With the upgrading of thermal spray equipment, the particle speed has been continuously improved, and the quality of the coating has been continuously improved.

Supersonic atomization decreases the particle size and the roughness of the coating. Roughness is an important performance index of the coating, which depends on the particle size of atomized particles. The supersonic atomization enhances the effect of the gas flow on the molten metal at the end of the wire, and the atomized particles are fine and uniform, which greatly reduce the roughness of the coating. At the same time, with the reduction of the particle size, it also reduces the spatter in the flattening process of the particles and helps reduce the porosity of the coating. Supersonic atomization is the starting point for supersonic arc spraying, and it is the fundamental difference from ordinary arc spraying. Supersonic arc spraying equipment includes power supply, spray gun, wire feeding mechanism and accessories, and the key equipment is supersonic arc spray gun.