Plasma surfacing ,also named Plasma Transferred Arc,is one of the main methods of surface treatment for cemented carbide finishing,which is widely used in petroleum, chemical, construction machinery, mining machinery and other industries, such as the sealing surface of some valves Repairing after welding, oil drilling pipes, bearings, etc.
Plasma surfacing can also be called plasma cladding and plasma spray welding, which is a cladding method that uses plasma arc as a heat source to melt the added metal and make it combine with the base metal as a metallurgical combination. Plasma surfacing uses the plasma generated between the tungsten electrode of the welding torch as the negative electrode of the current and the substrate as the positive electrode of the current as heat, and transfers the heat to the surface of the workpiece to be welded, and sends welding powder to the heat energy area. It melts and deposits on the surface of the workpiece to be welded, so as to realize the strengthening and hardening process of the surface of the part.
Compared with other cladding technologies, plasma surfacing welding has the following main features:
1. Compared with argon tungsten arc welding, plasma surfacing has strong controllability of penetration depth, high cladding speed and high productivity. After cladding, the interface between the base material and the cladding material is in a metallurgical bonded state with high bond strength, low heat input and low dilution rate. More importantly, due to the poor ability of the tungsten electrode to carry current, a larger current in argon arc welding will cause the tungsten electrode to melt and evaporate, and its particles may enter the molten pool and cause pollution, while in plasma cladding Tungsten electrodes need to withstand less current.
2. Compared with manual arc welding, although it is slightly inferior in application flexibility and convenience, welding torches show obvious advantages in terms of production efficiency, and manual arc welding is labor-intensive, which affects workers' health and product quality,which is greatly affected by the level of workers and the quality of welding rods.
3. Compared with submerged arc welding, it has greater flexibility in welding position. In addition, the plasma arc itself has the advantages of concentrated heat at the arc center, stable arc, and low dilution rate.
4. Compared with other surfacing welding, the mutual fusion between the base material and the cladding material is less during the plasma surfacing process, and the change of the characteristics of the cladding material is small.
In addition, the use of powder as the cladding material can improve the design freedom of the alloy and make it possible to clad the material, thereby greatly improving the wear resistance, high temperature resistance and corrosion resistance of the working piece. Therefore, plasma surfacing is widely used in new product manufacturing and equipment manufacturing in petroleum, chemical, engineering machinery, mining machinery and other industries.
