Resources - PTA Process
A plasma arc is established by ionizing argon gas passing through an electric arc formed between a non-consumable tungsten electrode(-) and copper plasma nozzle(+) inside the welding torch.
A second electric arc is then established between the tungsten electrode and the work piece through the ionized gas stream. This is called the “Transferred Arc”
The Transferred arc is constrained by the plasma nozzle resulting in a “plasma column” with temperatures between 10000 ºC and 15000 ºC. The energy released by the arc is proportional to the amount of current applied to the arc and the arc length.
Powdered metal is fed at a controlled rate into and /or around the plasma stream through injection ports and is subsequently heated by the arc.
The relationship between plasma energy and powder feed rate determines the amount of “arc energy” remaining to melt the work piece. As a result, extremely good control over the depth of penetration into the work piece is achieved.
Shielding gas is delivered through the large outer nozzle, protecting a substantial area around the plasma from oxidation.
An elaborate cooling system is required to maintain plasma torch temperatures at sustainable levels.