What are the types of plasma arcs in plasma spraying technology?

Due to the global energy shortage, facing the comprehensive development of oil and coal, we must research new energy on our own. Although clean energy is being developed and used, it still cannot meet the needs of a large population. Therefore, some countries use nuclear energy. At this point, we have to mention plasma. Plasma can be divided into three categories. One type is high-temperature and high-pressure plasma, with temperatures in the billions of degrees, which can be used for nuclear fusion research. The second type is low-temperature and low-pressure plasma, with an ionization degree of less than 1% and a temperature of only 50-250 degrees. The third type is high-temperature and low-pressure plasma. More than 1% of the gas is ionized, reaching temperatures of tens of thousands of degrees. Plasma spraying used in industry is the third type.

Plasma spraying can make the substrate surface have wear resistance, corrosion resistance, high temperature oxidation resistance, electrical insulation, thermal insulation, radiation protection, wear reduction, and sealing properties. Using a plasma arc driven by direct current as a heat source, materials such as metals and alloys can be heated to a semi molten or molten state and sprayed at high speed on the surface of the pre treated workpiece to form a strong surface layer.

China's economic strength continues to grow, and the protection of materials and workpieces has also received a lot of attention from many people. At present, the demand for plasma spraying equipment in China is constantly increasing, which is inseparable from plasma arc. At present, plasma arcs can be divided into three categories:

1. Non transfer arc

The connection between the positive electrode and the nozzle is not charged, and a non transfer arc will occur between the nozzle and the cathode. The working gas is heated by the arc between the cathode and the nozzle, causing complete or partial ionization, and then ejected from the nozzle. This plasma arc is used for particle spraying.

2. Transfer arc

When the arc leaves the spray gun, it will transfer to the plasma arc of the workpiece. In this case, the nozzle is not connected to the power supply, the workpiece is connected to the positive electrode, and the arc flies between the cathode and anode of the spray gun. The working gas enters around the arc and is then ejected from the nozzle. This plasma arc is used for plasma arc cutting, plasma arc welding, and plasma arc melting.

3. Composite arc

The non transfer arc ignites the transfer arc and heats the metal powder, while the transfer arc heats the workpiece to produce a molten pool on the surface. In this case, both the nozzle and the workpiece are connected to the positive electrode. This plasma arc is currently used for plasma jet welding. During plasma spraying, a direct current arc is generated between the cathode and the nozzle. The arc heats and ionizes the introduced working gas into high-temperature plasma, and the nozzle sprays a plasma flame. The outlet temperature of the nozzle can reach 15000-20000 ° K, but it decays quickly. The powder is melted into the flame by feeding powder gas, accelerated to over 150m/s by the flame flow, and sprayed onto the substrate to form a thin film.

Plasma spraying technology has always been a key focus of development in China, so technicians must understand this knowledge. If you want to learn more, you can follow us more at Yancheng Hongjie Petroleum Machinery Co., Ltd. We will answer your questions in a timely manner.