Plasma Transferred Arc

PTA stands for Plasma Transferred Arc, it uses electricity to create an arc which passes between the PTA torch and the workpiece. This arc creates a molten pool on the surface of the parent material to be overlaid. A metal powder is then fed into the molten pool to create a metallurgical bond with the parent material. There is a wide range of powders available for PTA overlay from stainless alloys to tungsten carbides.

The German designed and constructed PTA system further enhances the range of Thermal Spray services the DCL Engineering Group can extend to our customers.

Applications include

  • Stellite™ overlays for high temperatures
  • Valve seats
  • Wire Drawing Capstans
  • Bearing positions for high compressive loads
  • Tungsten Carbide Wear Resistant overlays
  • Ball Valves
  • Valve Stems
  • Sucker Rods
  • Replacing Worn Splines
  • Guide Rolls
  • Forming Dies
  • De-watering Screws

Drive Spindle

Drive Spindles are subjected to very high compressive loads in service, for this reason neither Arc Spray or High Velocity coatings offer the best solution. After pre-machining 0.5mm per side the two bearing journals have been rebuilt with a metallurgically bonded PTA overlay of NiCrSiB. The deposit hardness is in the region of HRc 40-45 and after slow cooling to ambient temperature the journals are proof machined and finally ground to tolerance.

Shear Blade

By understanding the environment that these shear blades are subjected to, DCL are able to offer the customer a 'preferred wear' scenario. The shear blades have a slightly softer deposit applied to them than the anvil, ensuring that the shear blades wear preferentially.

Pinion Shaft

When the bearings on the pinion shafts spin, it causes damage to the journals and due to the heavy loads the pinion carries DCL recommend a metallurgically bonded overlay of nickel, chrome, silicon, boron with the PTA System. Any damaged material is first removed by pre-machining, 2mm of overlay are then applied and finished by grinding to give the best surface finish.

Wedge Shaped Gate Valves

Subjected to a tough environment with the combined effects of corrosion, erosion and high temperature. The sealing faces to be rebuilt are first ground flat, a PTA overlay of Stellite 6™ is then applied to a thickness of 3mm and after slow cooling in a box of vermiculite the valve heads are then ground to final dimension. The resulting PTA overlay outlasts the original component in-service by up to 2.5 times.

Alloy selection

  • Stellite® Alloys
  • Tungsten Carbides
  • Hastelloy
  • Inconel® Alloys
  • Aluminium Bronze
  • Tool Steels
  • NiCrSiB Alloys
  • Stainless Steels (300, 400)
  • Custom Blends

Plasma Transferred Arc (PTA)
Plasma Transferred Arc (PTA)

Plasma Transferred Arc (PTA)

Plasma Transferred Arc (PTA)

Sizer screen
PTA deposit

PTA deposit
PTA deposit

Overlaid
Overlaid