The PTA (Plasma Transferred Arc) Welding process is a melt welding process suitable for hardfacing on wear and / or corrosion of mechanical workpieces with superalloy metal powders. The PTAW welding process and equipment is a modification of the Gas Tungsten Arc Welding (GTAW).
The PTA process is characterized by the high density plasma arc obtained by ionizing Argon gas passing through an electric arc formed between the non-consumable tungsten electrode (-) and the copper (+) plasma nozzle into the welding torch (pilot arc).
The second electric arc, called the Transfer Arc, produces the energy needed to melt the base metal and filler metal. The transferred arc is “restricted” to a greater temperature increase to obtain a plasma column with a temperature between 8,000 ° C and 18,000 ° C.
The significant difference with GTAW is in the torch arc which serves to provide the concentration and collimation of the arc plasma. With the aim to produce arcs and plasma at a certain limit to be followed by the release of high temperature ionized plasma through the arc hole.
The diameter, configuration and esophageal length of the arc holes are carefully designed to maximize the desired arc properties, namely peak, high temperature and stability. Hole details are interchangeable so variations in these dimensions are available to suit a wide range of welding requirements. The hole concentrates the plasma arc and unites the flow thus assuming a beam configuration as opposed to the “umbrella” arc of the GTAW process.
Types of Plasma Arc Welding:
Based on the method used, plasma arc welding is divided into two types, namely:
- Transferred plasma arc welding, where the arc is sent from the electrode to the workpiece because the workpiece is / is involved in the electrical circuit.
- Non-transferred plasma arc welding, in which an arc is formed between the electrode and nozzle. Furthermore, heat is channeled to the workpiece with plasma gas. This heat transfer is similar to the oxyfuel flame welding process.