Metal spraying technology
Metal spraying technology involves applying metal or alloy materials to substrate surfaces through a specific process, creating a coating with specialized properties. It plays a vital role in aerospace, machinery manufacturing, petrochemicals, and other fields. The core of this technology is to use a heat source to heat the spray material to a molten or semi-molten state. This material is then atomized and sprayed onto the pretreated substrate surface using a high-speed airflow. The coating and substrate form a strong bond through mechanical bonding, physical adsorption, or micro-metallurgical bonding. Depending on the heat source, metal spraying technology can be categorized into flame spraying, arc spraying, plasma spraying, and other types, each with its own unique characteristics and scope of application.
Flame spraying is an older method of metal spraying. It uses an oxyacetylene flame as a heat source to melt the spray material (typically wire or powder). Compressed air then atomizes the molten droplets and sprays them onto the substrate surface. Flame spraying equipment is simple, flexible, and cost-effective, making it suitable for repairing worn shafts, valves, and other components. However, the coating’s bond strength is relatively low, and its porosity is high, making it generally suitable for applications requiring less demanding coating performance. Arc spraying utilizes an arc generated between two charged metal wires as a heat source. The high temperature of the arc melts the wires, which are then atomized into fine particles by compressed air and sprayed onto the substrate surface to form a coating. Arc spraying boasts high efficiency and superior coating bond strength compared to flame spraying, making it widely used in the preparation of corrosion-resistant and wear-resistant coatings for large steel structures.
Plasma spraying uses a plasma arc as its heat source. The plasma arc reaches extremely high temperatures (reaching over 10,000°C), capable of melting materials with high melting points, such as metals and ceramics. During the plasma spraying process, the spraying material is fed into the plasma arc in powder form, instantly heated to a molten state. The material then impacts the substrate surface at high speed, driven by a high-velocity plasma stream, forming a dense, highly bonded coating. Plasma sprayed coatings offer excellent wear resistance, high temperature resistance, and corrosion resistance, and are widely used in the surface protection of high-temperature components such as aircraft engine blades and turbines. Furthermore, newer technologies, such as supersonic flame spraying, increase the flame velocity to achieve denser coatings and superior performance.
The coating performance of metal spraying technology depends on many factors. In addition to the type of heat source, the selection of spraying materials, the quality of substrate surface pretreatment, and spraying process parameters all have an important impact on the coating quality. The composition of the spraying material should be selected according to the use environment and performance requirements. For example, components working in high-temperature environments need to choose high-temperature resistant alloys or ceramic materials; in corrosive environments, corrosion-resistant metals or alloys should be selected. The purpose of substrate surface pretreatment is to remove surface impurities, increase surface roughness, and improve the bonding strength between the coating and the substrate. Commonly used methods include sandblasting, phosphating, and anodizing. Spraying process parameters such as spraying distance, spraying angle, and heat source power need to be precisely controlled to ensure uniform coating thickness and stable performance.
With the continuous advancement of science and technology, metal spraying technology is developing towards higher efficiency, precision, and intelligence. The development of new spraying materials, such as nanocomposite coatings, has significantly improved coating performance, offering enhanced wear resistance, corrosion resistance, and oxidation resistance. Furthermore, the application of computer simulation technology in the metal spraying process can optimize spraying process parameters, predict the coating formation process and performance, and reduce testing costs and time. In the context of Industry 4.0, metal spraying production lines are integrated with technologies such as the Internet of Things and big data to enable real-time monitoring and intelligent adjustment of the spraying process, further improving coating quality stability and production efficiency, and providing strong support for the development of the high-end equipment manufacturing industry.
