Product category:
Thermal and weld hardfacing, coating and overlaying
News Release from: Arcraft Plasma Equipments (I) Pvt | Subject: PTA hardfacing
Edited by the Manufacturingtalk Editorial
Team on 31 January 2003
Plasma arcs provide precise alloyed
coatings
Plasma transferred arc welding produces a very high quality, precise wear-resistant alloyed metal deposit on mechanical parts with minimal dilution or deformation of the base material.
Plasma transferred arc welding produces a very high quality, precise wear-resistant alloyed metal deposit on mechanical parts with minimal dilution or deformation of the base material Plasma derives its novel operating characteristics from the advanced torch design
This article was originally published on Manufacturingtalk on 16 Dec 2002 at 8.00am (UK)
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However, in the plasma torch, the electrode is positioned behind a copper nozzle with a central orifice.
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If a constricting orifice is placed around the arc, the amount of ionization, or plasma, is increased.
This results in a higher arc temperature and a more concentrated heat pattern than exists in TIG welding.
Plasma torch designs exist for various applications like cutting, welding, hardfacing, cladding, spraying, melting, heating etc.
This articles discusses the use of a special adaptation of the plasma welding torch for hardfacing and cladding.
The process is called PTA hardfacing when it is used for wear resistance and PTA cladding when it is used for corrosion resistance.
The system consists of: 1.
Electrode; 2.
Plasma nozzle; 3.
Powder feed nozzle; 4.
Shielding nozzle; 5.
Work piece; 6.
Ballast resistance; 7.
Power source; 8.
Oscillation unit.
PTA process - Plasma Transferred Arc System (PTA) is a high energy, inert gas welding process.
Argon gas is basically used for arc plasma supply, powder transport and molten material shielding.
It produces a very high quality deposit offering optimal protection with minimal dilution or deformation of the base material.
It is a process that deposits very precise coatings of perfectly controlled alloys on mechanical parts that are subject to intense wear, significantly extending their service life.
The PTA system works with different metal powders as filler material, such as chrome carbide, tungsten carbide, and nickel- and cobalt-based powders.
Future development could also see the use of ceramic-based powders.
Using these hard-wearing materials can improve the durability of the weld.
A wide range of overlay alloys is available for practically any part.
Some alloys are very hard, others are softer with hard abrasion-resistant particles dispersed in a matrix.
Certain alloys are made to rebuild a part to a required dimension while others are designed to be a final overlay that protects the work surface.
When used to deposit powder metal alloys on a substrate, the PTA system has a dilution level of 3 to 7%.
Compare this to submerged arc systems, which can dilute the base metal by as much as 40%.
Combined with a narrow heat-affected zone, the PTA system's low dilution rate prevents undesired substrate changes and can enhance the alloy's wear performance in applications for manufacturing wear components.
It also results in a smooth surface finish for easier and quicker finishing and machining.
PTA technology is particularly effective in protection against corrosion, thermal shock and abrasion.
The PTA welding system can deposit metal alloys on metal surfaces at rates of up to 20 lb/h.
The system can be fitted with automated manipulators to handle different parts, even those with complex shapes and narrow tolerances Benefits of hardfacing/cladding: 1.
Reduces Cost: Restoring a worn part to "as new" condition generally costs between 20-70% of a brand new replacement part.
2.
Prolongs Equipment Life: Service life increases of 3 to 10 times are common with properly overlaid parts.
3.
Reduces Downtime: Parts last longer and fewer shutdowns are required.
4.
Less Spare Parts Inventory: There is no need to keep numerous spare parts when worn parts can be rebuilt.
Applications - typical application areas of the PTA technology are extruding machine screws, valves, valve seats of internal combustion engines (motorcar, marine, locomotive etc), accessories for ships, petroleum chemistry and power generation, cutting tools (milling cutters, broaches, knives),Equipment for mining, crushing, rolling, road building and tunneling, Process equipment in ceramics and cement production,moulds and forging dies, pulp and paper industry equipment, agricultural equipment, parts for nuclear plants, parts for chemical plants.
PTA deposits show the following characteristics: 1.
An attractive bead with no signs of oxidation, and with little or no ripple.
2.
Very low dilution.
3.
High, density, no porosity and no inclusions.
4.
Microphotos or x-rays show the deposits to be of high density and metallurgically bonded to the Substrate.
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