- THE PROCESS

PTA process is characterized by the use of a high density plasma arc as a heat source. The arc is formed between a non consumable electrode located within the body of the torch, and the work piece. The surfacing metal is added as powder.

Argon gas forms the plasma and transports the metal powder. A mixture of Argon with hydrogen up to 10 % shields both overlay and adjacent base metal from oxidation.

The nozzle in the torch constricts the plasma arc in an extremely columnar shape. This constricted plasma arc exhibits a very high thermal intensity, which makes it easier to concentrate the heat to the weld zone and to melt the filler metal more rapidly and efficiently.

Better thermal control results in a more consistent quality during welding and avoids overheating the work piece.

One major advantage of metal powder as a welding consumable when compared with wire or rod, is that it can be fed continuously through the arc to the weld pool.

This enables the deposit to solidify more evenly giving a better surface appearance and reducing weld porosity.

- THE EQUIPMENT

TBA produces two models. PTA 200 for manual applications that basically include the manual torch, the power supply, control unit, powder feeder and cooling system, and PTA 150 for automatized processes that consists of the same elements as the manual version plus a torch oscillator and manipulators for the work piece. The PTA 150 torch works mounted on the oscillator arm.

- ADVANTAGES

The process offers a combination of advantages that is not matched by any other welding method for applying wear resistant coatings. The main advantages are:

- The ability to apply tailor-made metal alloys that are only available in powder form.
- Low dilution and penetration, which reduces welding filler costs.
- A unique weld quality with homogeneous and pore-free structure.
- Easily mechanized and provides close control weld-profile.
- High deposition rates.
- Deposits between 0.01 and 0.250 inches (0.25 to 6.4 mm) thick can be produced rapidly in a single pass.

- COATING MATERIALS

Most currently used metal powders applied by this method can be classified as follows.

- Nickel Alloys (Ni-Cr-Si-B and Ni-Cr-Mo types).
- Cobalt base alloys (CoCrWC Stellite Types).
- Iron base alloys (Austenitic Types, Martensitic.
- Types, High carbon types, Stainless steels types, aggregatedWCtypes).

- TYPICAL APPLICATIONS

- Moulds and accessories for glass industry
- Diesel Engines Crossheads
- Extruder's screws
- Extrusion plungers
- Pump bushing
- Gate Valve inserts
- Oil drill tool joints
- Valve seats
- Wear rings
- Engine Valves
- Fluid Valves
- Steel work rolls and cylinders
- Hot Forging Dies
- Blades and knives
- ELECTRONIC OSCILLATOR