Stellite overlay with plasma welding
Plasma Transferred Arc Welding (PTAW)

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What is Plasma Transferred Arc?

Plasma Transferred Arc Welding is a true Welding process.  In a welding process the substrate surface is melted, and the metal cladding alloy metallurgically joined to the surface.  PTA uses a high energy plasma arc.  The arc transferred between a tungsten cathode and the substrate.

 

Plasma Transferred Arc (PTA) is an advanced coating process in which the powder is introduced into a combined arc/plasma. An arc is transferred to the substrate where it melts, in a controlled way, the base material. The powder is introduced into the transferred arc and deposited on the surface of the substrate. The coating formed has a metallurgical bond, with a small diffusion zone. Due to the metallurgical bond the bond strength is extremely high.

PTA has several advantages over other coating technologies, such as the possibility to form coatings that can vary in thickness from 0,5mm to 2 cm. The transferred arc results in a relative low heat into both the coating materials as well as the base material. Especially for hard materials, such as carbides, this low heats into limits the dissolution of carbides. The low heat input also limits the transfer in the microstructure of the base material.

Teknokraft Plasma transferred arc weld deposits have a low amount of dilution.  Dilution is usually less than 5%.  Low dilution means the surfacing alloy is of the highest purity.  High purity gives the best wear life in the field.

Our procedures carefully control the heat input to avoid stress and distortion caused by normal welding.

What Alloys are used?

Normally Teknokraft applies Stainless steel alloys, nickel alloys, and Stellite alloys.

For wear protection against fine particle abrasion the alloy used is TA70.  This is a 65% Macro Crystalline Tungsten carbide alloy, mixed in a NiCrBSi matrix.  It offers the best combination of Abrasion and Impact resistance and cosmetic appearance.

Welding Procedure

This is a true welding process with all of the advantages and some of the disadvantages of welding.  Our procedure requires a preheat of the base metal, and slow cooling.  The shaft is slowly rotated during welding so that the heat is uniform.

Teknokraft Experience

We have used this process on Drilling and Shock tools, Stabilizers, Radial bearings, Compressor shafts, Winding blocks for overhead cranes, motor shafts, valve seats, gates, etc.  This has all been done with 100% field success.  The part performs and the customer never complains.

Preparation and lead time are determined on a case-by-case basis.  Please send drawing and estimated time of delivery of the part.

Teknokraft PTA Welding Notes:

The Plasma Transferred Arc process (PTA) technology was developed in 1962.  The Teknokraft PTAW process is focused on cladding and overlays.  We have been doing cladding since 1995.

Plasma Transferred Arc Welding (PTAW)
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