Every metal is at risk of corrosion. For some, corrosion occurs purely through exposure to oxygen in the air and is difficult to combat. For others, it is much slower, more gradual, barely noticeable, and rarely a problem. Regardless of the type of metal, given enough time, it will eventually show signs of rust.
The most effective method of preserving metal quality in any build is by applying a corrosion-resistant layer on all exposed surfaces. These layers protect the metal elements from exposure and drastically reduce the rate of corrosion from all sources. There are many different methods of applying these corrosion-resistant layers, but some are better than others.
Plasma transferred arc welding (PTA) is an especially effective method for applying a protective outer coating. It uses a plasma arc to treat, coat, and seal the metal, forming a highly resistant and reliable layer.
How is Plasma Transferred Arc Welding Accomplished?
PTA works similarly to traditional arc welding but involves using an additional filler material (usually a superalloy metal powder or a rod of the same metal). These filler materials can form one of two types of welds: hard surfacing or corrosion resistant.
The process creates a high-energy plasma arc between the torch’s electrode and the base material being welded. This arc runs along the seam, melting the surface of the base metal. This filler material is fed either into the back of the weld pool (if in wire form), through the torch (if in powder form), and into the arc before reaching the pool. The resultant bonded overlay formed with this filler material integrated into it, is a much stronger weld.
The filler materials used in plasma transferred arc welding are typically:
- Stellite
- Colmonoy
- Hastelloy
- Tungsten Carbide
Due to the higher temperatures achieved with PTA, there is very little dilution of the filler, allowing the metal to maintain its native properties after welding. Thus, they retain their corrosion resistance and hardness, making products much stronger, less brittle, and more reliable.
The process of PTA is faster than TIG or MIG welding and is typically performed using automation, making it a fast method to perform predictable welds.
What are the Benefits of Plasma Transferred Arc Welding?
Welders and fabricators typically use PTA due to its anti-corrosive properties. These traits help strengthen metallic projects by melting the superalloy metal powders into the very surface of the cutting metal. However, plasma transferred arc welding has other notable benefits beyond this.
For instance, physically applying a layer of metal powders adds tensile strength to the base metals and composites. This improves the overall strength of the metal, providing a greater degree of rigidity and allowing for greater longevity.
PTA methods also trump conventional forms of welding. The handheld nature of the cutting tool provides weldability limited only by the user’s ability. You can use it at any angle, length, and location, making it ideal for any difficult-to-reach job. The plasma arc is also adjustable to the user’s needs.
Furthermore, PTA provides a high-energy arc at a far lower heat than standard arc welding. This will limit the amount of slag or unwanted cutting and leave a far more secure join. The remaining weld will be almost void-free, without any oxide films or discontinuities in the cutting line. Overall, this makes the weld far less prone to chipping with minimal dilution.
Other benefits include:
- Significantly lower costs than other forms of hard facing – The gases used also result in less loss of filler than Tungsten Inert Gas (TIG) and Metal Inert Gas (MIG) processes. This provides a far greater ratio of quality to price in materials.
- More economical and reliable results – Not only is it more cost-effective to use PTA welds, but saves money in the long run. Harder, tougher surfaces require far less maintenance or repairs and will remain reliable much longer.
- Higher productivity for users – The methods used to create the covering layers are reliable and homogenous. This means every weld yields predictable and consistent results, leading to fewer quality issues and greater output.
- Uses less base material per weld – The lower dilution ratio for the metal powders used ensures a consistent result using fewer materials.
- Smaller heat-affected zone – The precise arc, speed, and higher temperature reduce the area affected by the plasma heat. This makes PTA methods better for smaller or more precise weld spots.
Applications of Plasma Transferred Arc Welding
The stronger nature of welds made using PTA methods make them ideal for use in any products exposed to intense weight, pressure, or torque. Some of these uses include:
- Slurry transport and other high-wear piping components
- Ground-breaking equipment used in mining or oil sands industries
- Valve components (gates, seats, valve stems, etc.)
- Wire-based overlays
- Turbine blades, shafts, bearing surfaces, and other power generation equipment
- Riser equipment
PTA methods are an ideal choice for almost any job. A plasma transferred arc welding machine can work well in tandem with your industrial cnc plasma table. When components or tools require powerful joins, plasma transferred arc welding is the best option. The alloy-strengthened joins provide much greater strength and corrosion resistance, and it’s also cheaper.
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