Current Situation and Development Trend of Plasma Spraying Equipment at Home and Abroad

       1 Foreign plasma spraying equipment

1.1 Axial III plasma spraying equipment

Axial III three-electrode axial powder feeding plasma spraying system

Axial III is a three-cathode axial powder-feeding plasma spraying system developed by Mettech, Canada. The traditional method of powder feeding outside the gun is to send the powder radially into the plasma flame, so that part of the powder passes through or does not enter the plasma flame, which reduces the powder deposition efficiency and affects the coating quality. The Axial III can completely avoid these shortcomings. The Axial III axial powder feeding spray gun includes 3 pairs of independent anodes and cathodes. After the gun starts arcing, the 3 arcs are collected at the nozzle through a concentrator, and the powder is sent to the nozzle collection point through a powder feeding tube located in the axial direction of the spray gun. So as to realize the true axial powder feeding. Compared with traditional powder-feeding plasma spraying equipment outside the gun, the main advantages of Axial III are high deposition efficiency, high powder-feeding rate, low porosity and higher coating hardness, and less demanding on powder particle size distribution. For example, when spraying Cr 2O 3 with Axial III, the deposition efficiency is 45%-75%, the powder feeding rate is 30-90g/min, the hardness (HV300) is 1300-600, and the porosity is 0.3%-0.5%. Since Axial III improves powder deposition efficiency, spraying costs are reduced accordingly. For example, when spraying WC-Co, Axial III can save 75% to 80% of the time compared to HVOF. At present, the use of thermal spraying process to replace chrome plating has become a new research direction. Axial III has replaced chrome plating in many fields, including WC-Co, Cr-NiCr, Ti, NiCrBSi. In addition, Axial III also has obvious advantages in preparing coatings with higher requirements, such as anilox roller coating, newspaper printing roller coating, etc.

How Axial III Works

At present, it is difficult to greatly improve the coating quality by using the traditional powder feeding method from outside the gun. The Axial III achieves true axial powder feeding, which has the potential to bring the quality of plasma sprayed coatings to a new level.

1.2 Multicoat plasma spraying equipment

Multicoat is the latest plasma spraying equipment developed by SulzerMetco, the largest thermal spraying company in the world. The design of Multicoat is based on the concept of "platform", that is, using the same main platform, equipped with different hardware and software and corresponding components, different spraying processes can be realized. The main platform consists of an operating console, a process control center and a gas management center. This is the first time that SulzerMetco has combined the advanced nature of a PC (process reproduction, data management) with the robustness of a PLC. Multicoat can perform atmospheric plasma spraying (APS), vacuum plasma spraying (VPS) and hypersonic flame spraying (HVOF). In terms of system equipment, Multicoat includes operation console, process control center, gas management center, heat exchanger, powder feeder, transfer cabinet, power supply, spray gun, etc. Compared with the previous plasma spraying equipment, Multicoat separates the gas part, which can not only avoid the interference of other circuits on the mass flowmeter, but also avoid the danger of hydrogen leakage, which improves the safety of the system.

1.3 5500-2000 plasma spraying equipment

5500-2000 is a plasma spraying system developed by the American company PRAXAIR-TAFA. The 5500-2000 uses proprietary software to control and monitor the actual energy of the plasma arc, the net energy, in real time. The use of a net energy algorithm can bring the closed-loop control of plasma spray systems to a new level. After the operator enters the optimized parameters, the control module controls the entire process, monitors and displays the efficiency of the spray gun in real time, makes the system parameters respond to the conditions of the spray gun, and makes corresponding adjustments to maintain the target plasma energy and provide a stable energy output level.

In addition, PRAXAIR-TAFA has also developed a multi-functional spraying system GTS similar to Multicoat, and a high-power plasma spraying system PlazJet (spraying power can reach 200kW), of which GTS can be used for plasma spraying, supersonic flame spraying and arc spraying. PlazJet has several users in China.





2 Domestic plasma spraying equipment







2.1 GP-80 plasma spraying equipment



GP-80 type plasma spraying equipment is a plasma spraying equipment successfully developed by Beijing Institute of Aviation Manufacturing Engineering in the 1970s. Its components are GDP-K type control cabinet controlled by relay and float flowmeter, magnetic amplifier diode rectifier GDP-80 type power supply, SR-1 type heat exchanger cooled by tap water, powder feeding wheel type SF-1 type powder feeder, PQ-1S portable spray gun, PQ-1J machine-mounted spray gun, which are easy to operate and protect The links were perfect, representing the highest level of domestic plasma spraying equipment at that time, and contributed to the promotion of plasma spraying technology by the State Science and Technology Commission. Later, through technology transfer, this equipment became the mainstream product of domestic plasma spraying equipment. At present, this type of equipment still accounts for more than 80% of domestic plasma spraying equipment.







2.2 APS-2000 plasma spraying equipment



APS-2000 is the latest plasma spraying equipment developed by Beijing Institute of Aeronautical Manufacturing Engineering. Due to the shortcomings of GP-80 power supply, low heat exchanger efficiency, low current and gas flow control accuracy, etc., the quality of the sprayed coating is not very stable, and it is difficult to meet the requirements for high-quality coatings. Therefore, in 1995, the Key Laboratory of High Energy Beam of Beijing Institute of Aeronautical Manufacturing Engineering developed a new generation of APS-2000 plasma spraying equipment. The equipment adopts many new technologies, its main components are APS-2000K type control cabinet with PLC and mass flow meter, K-800 type power supply with thyristor rectifier, Freon refrigeration air-cooled FL-1 type heat exchange It can prevent mutual interference and improve the The overall performance has reached the level of foreign countries in the 1990s, representing the highest level of domestic plasma spraying equipment at present.







3 Conclusion



With the enhancement of my country's economic strength, the protection of material workpieces has attracted more and more attention, and the domestic demand for plasma spraying equipment and processes has also greatly increased. In general, compared with foreign advanced plasma spraying equipment, there is still a certain gap between domestic equipment, mainly in the control system. At present, the Key Laboratory of High Energy Beam of Beijing Institute of Aeronautical Manufacturing Engineering is developing a more advanced PC+PLC control system, hoping to gradually shorten the gap between domestic plasma spraying equipment and the international advanced level. (end)