PTA Description
The plasma transferred arc (PTA) process is based on plasma principles and is regarded as an improvement on tungsten inert gas (GTAW) welding. The high energy concentration is attributable to the use of a taper nozzle, which limits the arc column diameter between a tungsten electrode and the workpiece in an inert gas atmosphere, typically argon.
The filler material is conveyed by a gas stream into the plasma jet. The gas may be inert, active, or a mixture of both. A third gas stream protects the molten metal pool against atmospheric contamination. Given that mixtures of active and inert gases can be applied, argon is typically employed for all three-gas systems.
PTA Applications
- Hard surface coating: The PTAW process is effective for depositing hard alloys to enhance wear resistance. Stellite, Colmonoy, Hastelloy and tungsten carbide have all been deposited successfully using PTAW.
- Corrosion resistant overlay coatings: Due to the localised heat input in the PTAW process, corrosion resistant alloys may be applied with very low dilution of the substrate. PTAW fulfils the requirement of underwater chemistry with less than 5% Fe in a coating thickness of just 0.040".
- Industries / Components:
- Non-magnetic drilling tools: drill collars, wear bands for MWDs, Flex Ponies, etc.
- Downhole components: Mud Motor Bearings, Stabilisers, Topsubs, Piston Subs Flow Restrictors, Drill Bits, etc.
- Flow control: valve bores, sleeves, seats, seat pockets, ring grooves, valve stems, etc.
- Power generation: turbine blades, shafts, bearing surfaces, etc.
- Riser components: pins, housings, etc.
Description of Laser Deposition Welding
Laser deposition welding is a welding process and an associated coating technology that complements thermal spraying. It is increasingly employed as an alternative to plasma transferred arc welding (PTA) in advanced weld repairs.
In laser deposition welding, the laser beam is defocused to a predetermined spot size on the workpiece. The powder coating material is introduced into the melt pool through a powder nozzle assisted by an inert gas. The laser optics and the powder nozzle traverse the surface of the workpiece to deposit individual tracks, entire layers or large volume build-ups.
Applications of Laser Deposition Welding
Laser deposition welding has gained recognition in industries including automotive, aerospace, marine, defence and others. In this process a laser heat source is used to melt a selected material onto a substrate. This forms a protective layer that is metallurgically bonded to the substrate with maximum deposition efficiency and minimal dilution (i.e. limited contamination by the substrate material that has melted).
The additional material may be applied as a powder or paste, which can be injected during the process or pre-placed, or by means of wire/strip feeding.
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Products
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Iron-based alloy
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Nickel-based alloy
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Cobalt-based alloy
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Cast/Melted WC
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Spheroidised WC
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Macrocrystalline
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Reference
A.S.C.M.D'Oliviera, R.S.C.Paredes, R.L.C. Santos: Pulsed current plasma transferred arc hardfacing, Journal of Materials Processing Technology 171, 2006, pp.167–174;
V.V.Diaz, J.C.Dutra, A.S.C.D'Oliveira: Hardfacing by Plasma Transferred Arc Process, INTECH, Ed. W. Sudnik, 2011, ISBN 978-953-307-642-3;
P.V. Senthill, A. Shirrushti: Finite Element Simulation of Plasma Transferred Arc Welding (PTAW) of structural steel, PV Senthill International Journal of Engineering Research and Applications, www.ijera.com, ISSN: 2248–9622, Vol. 4, Issue 10 (Part 4), October 2014, pp.06–11;
What is Plasma Transferred Arc Welding (PTAW), 12/01/2015, js, Accessed October 2015;
Simone Zanzarin: Laser deposition welding with metal powder. https://core.ac.uk/download/pdf/35317589.pdf
Converters & Calculators
