Thermal spraying technology - process principle - arc spraying - arc spraying

       

Arc spraying: An arc is generated between two wire-shaped metal materials, and the metal welding wire is gradually melted by the heat generated by the arc, and the melted part is sprayed to the surface of the substrate by the compressed air flow to form a coating. 

Arc spraying can be divided into DC arc spraying and AC arc spraying according to the arc power source. DC: stable operation, dense coating structure and high efficiency. AC: Noisy. The temperature generated by the arc is related to the arc gas medium, the type of electrode material and the current (such as Fe material, the current is 280A, and the arc temperature is 6100K). Generally speaking, however, arc spraying contains more heat than flame spraying powder particles, and the particles fly faster. Therefore, when the molten particles hit the substrate, the possibility of forming local micro-metallurgical bonds is much greater. Therefore, the bonding strength between the coating and the substrate is 1.5 to 2.0 times higher than that of flame spraying, and the spraying efficiency is also higher. Arc spraying also conveniently produces alloyed or "pseudo-alloyed" coatings. Different alloy compositions can be obtained by using two wires of different compositions and by using different feed rates. Arc spraying is similar to flame spraying equipment, and also has the advantages of low cost, low one-time investment, and convenient use. However, the arc spraying is obviously insufficient. The spraying material must be a conductive wire, so only metal can be used, and ceramics cannot be used, which limits the application range of arc spraying. In recent years, in order to further improve the performance of arc spray coating, foreign countries have made great improvements to equipment and processes, and published many patents. For example, methane or the like is added to compressed air as an atomizing gas to reduce the oxygen content of the coating. Japan also changed the traditional round wire into a square to improve the spraying rate and improve the bonding strength of the coating.