The Plasma Transfer Arc Torch (PTA Torch) is the centerpiece of a Plasma Transferred Arc (PTA) machine, responsible for generating the plasma arc and delivering the alloy powder precisely to the weld area. Its structure and working principle are different from the ordinary welding torch, with higher precision and stability.
1. Structural components
The PTA welding torch is mainly composed of the following parts:
Cathode (tungsten electrode): the core component for generating plasma arc, usually made of high temperature and corrosion resistant tungsten material.
Anode (nozzle): guides the plasma arc and concentrates the arc column, usually made of copper to improve heat dissipation.
Powder feeding system: Used to uniformly feed the alloy powder into the plasma arc, so that it melts and deposits on the surface of the workpiece.
Protective gas channel: Argon or helium is usually used as plasma gas and protective gas to prevent oxidization in the welding area.
Cooling system: Water cooling is used to ensure the stability of the welding torch during high-temperature operation.
2. Working principle
Arc initiation stage: High frequency and high voltage pulse generates non-transfer arc between tungsten electrode and nozzle (small current, stable arc initiation).
Plasma arc formation: plasma gas (such as argon) through the nozzle, by the high temperature arc ionization into high energy plasma, and through the nozzle to the surface of the workpiece, the formation of the transfer arc (the main arc).
Powder feeding and melting: the alloy powder is uniformly fed into the plasma arc area through the powder feeder, instantly melted and sprayed onto the surface of the workpiece to form a dense coating.
Metallurgical bonding: The melted powder is metallurgically bonded with the base material to form a high-strength, wear-resistant cladding layer.
3. Features and advantages
High energy density: long, thin arc columns, high temperatures (up to 20,000°C), precise control of melt depth and coating thickness.
Small heat-affected zone: Reduces substrate deformation and thermal stress, improves dimensional stability of the workpiece.
High material utilization rate: the powder material utilization rate is over 90%, which is economical.
Excellent coating quality: dense coating, no porosity, high metallurgical bonding strength, excellent abrasion and corrosion resistance.
4. Commonly used materials and applications
Alloy powder materials: cobalt-based, nickel-based, iron-based, tungsten carbide and other wear-resistant, corrosion-resistant alloy powder.
Typical application areas:
Oil and gas: Wear-resistant and corrosion-resistant coatings for valves, drill bits and pump bodies.
Engineering machinery: shafts, rolls, gears, mold surface strengthening and repair.
Metallurgical industry: surface surfacing and repair of rolls, molds, valve seats and other parts.
5. Precautions for use
Tungsten electrode protection: prevent oxidization and burnout, prolong electrode life.
Nozzle cooling: maintain good water cooling effect to avoid nozzle overheating damage.
Powder feeding stability: ensure uniform powder feeding to avoid uneven coating thickness or slagging defects.
Safety protection: high temperature, high voltage operation, need to be equipped with protective masks, gloves and other safety equipment.
6. Comparison with other welding methods
With plasma arc welding (PAW): PTA welding is mainly used for surface cladding and strengthening, while PAW is mostly used for penetration welding.
Comparison with Laser Surfacing: PTA welding is cheaper and applicable to a wider range of materials; however, laser surfacing has a smaller heat-affected zone and higher precision.
With plasma spraying: PTA welding is metallurgical bonding, high coating strength; plasma spraying is mechanical bonding, suitable for thin layer coating.
Post time: Feb-19-2025