Plasma spray gun used for low-pressure plasma spraying

Abstract

The invention discloses a plasma spray gun used for low-pressure plasma spraying, and belongs to spray equipment used for preparing metal and metal oxide or metal carbide coatings. The spray gun comprises a gun body, a cathode, an anode and a spray nozzle, wherein a club-shaped cathode with a conical head is arranged in the gun body; an external water-cooling cylindrical anode and an internal compressed spray nozzle which is connected with the cathode closely are arranged in front of the cathode along the axial direction; and a spray powder material is fed into the inlet of the spray nozzle, is heated and accelerated in the spray nozzle, is heated in plasma in a low-pressure environment after being sprayed out from the spray nozzle, and flies to the surface of a spraying workpiece. The positive electrode of a direct current power supply is connected with the anode while the negative electrode is connected with the cathode. The device of the invention has high powder heating capacity and is suitable for performing plasma spray in low-pressure or ultra-low-pressure environment.

Description

technical field [0001] The invention relates to a spraying equipment for spraying metal, metal oxide or metal carbide, in particular to a plasma spray gun. Background technique [0002] Plasma spraying is the use of electric energy to convert mixed gases such as argon, hydrogen or helium into high-temperature plasma and form a plasma jet in the anode, and use its high-temperature and high-speed plasma gas flow to spray metal or metal oxide and metal carbide onto the workpiece. The surface, the process of forming the coating. The temperature, velocity and pressure distribution characteristics of the plasma jet strongly affect the degree of melting of powder particles injected into the plasma, the porosity and hardness of the coating. The distribution of plasma temperature and velocity outside the spray gun not only depends on the structural characteristics of the plasma generator, but also depends on the pressure of the surrounding environment outside the plasma spray gun. ...

AI Technical Summary

Problems solved by technology

In short, the power of spray guns used for low-pressure or ultra-low-pressure plasma spraying at home and abroad is much higher than that of plasma spraying under atmospheric conditions, and low-pressure plasma spraying is difficult to spray materials with high melting point and low thermal conductivity like zirconia.

The biggest advantage of this method of feeding powder from the anode inlet is that the powder is heated well, and the deposition efficiency of the powder during spraying is high. The disadvantage is that the powder is easy to accumulate inside the nozzle, causing coating quality problems. Commercial plasma spraying is less used

The inventor once designed and manufactured internal powder feeding plasma spraying equipment, Chinese utility model patents ZL99243441.6 and ZL 02251688.3, ​​which can spray ZrO under atmospheric conditions with an input power of 6-8kW 2 -8Y 2 o 3 Powder material, and the deposition efficiency is more than 50%, but due to the internal structure design, it cannot adapt to low-pressure plasma spraying

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