Arc spraying technology
Arc spraying, a key branch of thermal spraying, has been a mature and highly effective surface protection and repair technology since its introduction in the early 20th century. Arc spraying, through continuous improvement, has evolved into a mature and efficient surface protection and repair technique. Initially used primarily for corrosion protection of metal components, its application has gradually expanded with advancements in equipment and materials to include wear-resistant reinforcement, dimensional repair, and functional coatings. It plays a significant role in industries such as machinery manufacturing, petrochemicals, electric power, and transportation. For example, spraying aluminum-bronze coatings on ship decks improves their wear resistance and anti-slip properties. Arc spraying nickel-based alloy coatings on worn machine tool guide rails can restore dimensional accuracy and extend equipment life.
The core equipment of arc spraying technology includes a power supply, spray gun, wire feed system, compressed air system, and control system. The power supply provides DC or AC power, with DC power being the most common, with an output voltage of 20-40V and a current of 100-500A. The arc power and wire melting speed are controlled by adjusting the current. The spray gun is a key component for arc generation and droplet atomization. It consists of a conductive nozzle, a gas flow guide, and other components. The conductive nozzle clamps and conveys the metal wire, ensuring a good connection between the wire and the power supply; the gas flow guide directs compressed air to form a high-speed airflow, atomizing and accelerating the droplets. The wire feed system uses a motor-driven roller mechanism to feed the wire into the spray gun at a set speed (typically 1-10m/min). The stability of the wire feed speed directly affects the arc stability and coating uniformity.
The compressed air system provides atomizing and accelerating gas for arc spraying. The compressed air must be dried and filtered to remove moisture and impurities. The pressure is typically 0.4-0.6 MPa, and the flow rate varies depending on the spray gun model, typically 3-10 m³/h. Low gas pressure results in poor atomization and a loose coating; high pressure causes the droplets to cool too quickly, reducing bonding strength. A control system coordinates parameters such as power supply, wire feed, and gas flow to ensure a stable spraying process. Some automated arc spray equipment is also equipped with a robotic arm or guide rails to enable automated spraying of complex workpieces.
The arc spraying process mainly includes substrate pretreatment, spray parameter setting, coating deposition and post-treatment. Substrate pretreatment includes surface cleaning, roughening and preheating, which is similar to plasma spraying, and its purpose is to improve the bonding strength of the coating. Surface cleaning removes oil and rust, and can be done by solvent cleaning or sandblasting; quartz sand or steel grit sandblasting is commonly used for roughening to achieve a surface roughness of Ra2.5-6.3μm; the preheating temperature is determined according to the substrate material, and steel parts are generally preheated to 80-150℃ to avoid cracks caused by excessive cooling of the coating. The spray parameter setting needs to be adjusted according to the wire material and coating requirements. For example, when spraying zinc-aluminum wire, the current is usually 200-300A, the wire feed speed is 3-5m/min, and the spray distance is 100-150mm; when spraying high-hardness alloy wire, the current and gas pressure need to be appropriately increased to ensure that the material is fully melted and atomized.
During coating deposition, the relative speed of the spray gun and substrate must be maintained uniform (typically 0.5-2 m/min). Multiple coats are applied to achieve the desired thickness, with each coat controlled at 50-100 μm to avoid cracking caused by excessive single-pass spraying. Post-processing is selected based on application requirements. Anti-corrosion coatings require pore sealing (e.g., epoxy resin coating) to fill pores and isolate corrosive media. Wear-resistant coatings may require grinding to improve surface finish and dimensional accuracy. Coatings subject to impact loads can undergo low-temperature heat treatment to eliminate internal stresses.
The development trends of arc spraying technology are toward high performance, automation, and multifunctionality. To achieve high performance, new alloy wires (such as high-chromium cast iron and intermetallic compounds) and composite wires (such as composite wires with a ceramic powder core) are being developed to expand the performance range of coatings. Automation is being pursued through the use of robotics and vision positioning systems to achieve precise spraying of complex components, improving coating uniformity and production efficiency. Multifunctionality is being achieved through the design of composite coatings (such as a base layer for corrosion protection and a surface layer for wear resistance), achieving comprehensive performance that is difficult to achieve with a single coating. Furthermore, environmentally friendly arc spraying technologies are also being developed, such as the use of inert gas shielding to reduce coating oxidation and the development of water-based sealants to replace solvent-based products, reducing environmental pollution. In the future, arc spraying technology will play a greater role in large-scale engineering protection, equipment remanufacturing, and other fields, providing strong support for energy conservation, consumption reduction, and sustainable development in the industrial sector.
