High-speed gas spraying technology
Author: langfeng Time: 2017-09-08
High-speed gas spraying technology
1 technical content and technical key
1) high-speed gas spraying equipment
High-speed gas spraying equipment is not complicated,it consists of spray gun,powder feeder, control system and gas supply system and other components.
1 - supersonic flame 2 - cooling water 3 - nozzle 4 - combustion chamber 5 - powder delivered by air flow 6 - cooling water 7 - oxygen 8 - gas
Jet Kote High Speed Gas Thermal Spray Gun
High-speed gas spray guns like a small rocket engine,Figure 2 shows the structure of the JetKote spray gun. It consists of a closed combustion chamber and a nozzle.The gas and oxygen are injected into the combustion chamber at a pressure of 0.5 to 3.5 MPa and a flow rate of up to 0.016 m3 / s. The mixture is continuously combusted and the combustion products are swollen and ejected from a long nozzle to form a supersonic flame. As a sign of high temperature supersonic airflow, you can see the flame in the bright and dark rhombic shock. The sprayed material of the powder is injected into the nozzle from the combustion chamber and the nozzle, into the center of the flame,and is heated and accelerated to obtain a high kinetic energy and is ejected from the nozzle. Spray particles will not be oxidized in the combustion products. As the particles are in the center of the flame, the oxidation is also slightly slight in the process of leaving the nozzle to reach the surface of the workpiece, and the temperature of the flame in the combustion chamber usually does not exceed 3000 ° C.The flame flow from the nozzle will be lower. Its speed is directly related to the combustion chamber pressure. The initial JetKote achieves an average flame speed of 1770 m / s, which can accelerate the WC-Co particle spray particles with a diameter of 5 to 45 m to a high flight speed of 315 m / s. This is far more than any other thermal spraying method can achieve the speed. But this is only the initial level of high-speed gas spray. By the beginning of 1984, the improved JetKote Ⅱ particle speed has greatly improved, the calculated particle speed to more than 800m / s. The hardness of the coated tungsten carbide coating has been significantly higher than that of the D-Gun coating.
The JetKote gun's combustion chamber is the handle of the gun, which is at right angles to the nozzle. This design is intended to facilitate the injection of powder coating material into the nozzle. Oxygen and gas combustion products from the combustion chamber through the four holes into the nozzle, spray powder at this site into the flame flow. Top Gun, HV-2000 and CDS spray gun in the gas burning at the same time will be powder injection, flame flow and the direction of the powder are axial. TopGun's gas injection system is uniquely designed to enable it to use a variety of gas, including acetylene. Other companies can not use acetylene spray gun as gas. While propane, propylene or hydrogen is used. Metco's DiamondJet has no combustion chamber and long nozzles. It uses a circular compressed air nozzle to constrain the gas flow, do not have to use water cooling measures, the gun is simple and lightweight. Tafa's JP-5000 is quite different from other guns. It uses kerosene as fuel, and the pressure of the combustion chamber is higher (up to 1.7MPa). The powder is injected from the throat of the radial combustion chamber and the nozzle. Due to the low pressure at this site, the mixing and heating of the powder with the flame stream is improved. Higher combustion chamber pressures provide higher particle velocities and higher coating quality.
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