Detailed explanation of plasma powder surfacing

       1: High plasma arc temperature and concentrated heat



Because the plasma arc has a compressive effect, its center temperature can reach 10000～50,000K, and its energy density can reach 10～10W/cm. Due to the high plasma arc temperature, the processed material is generally not limited by the melting point.



2: The plasma arc has good thermal stability



Since the gas in the plasma arc is fully ionized, the arc is more stable. Plasma arc current and arc voltage are not sensitive to changes in arc length within a certain range, that is, stable combustion can be maintained when the arc column is long, without the shortcomings of free arc floating easily.



3: The plasma arc is controllable



Plasma arc can adjust the thermal effect in a wide range. In addition to changing the input power, the heat energy and temperature of the plasma arc can be adjusted by changing the type of gas, the flow rate and the structural size of the nozzle; it can be adjusted by selecting different working gases Plasma arc working atmosphere; the arc density can be adjusted by changing the arc current, gas flow and nozzle compression ratio.



4: Principle of plasma arc surfacing in plasma powder surfacing equipment



Plasma arc is divided into two basic forms: transfer type and non-transfer type according to the power connection mode. The two poles of the transfer type power supply are respectively connected to the electrode and the workpiece, the arc burns between them, and the water-cooled nozzle acts as a contraction. The two poles of the non-transferable power supply are respectively connected to the electrode and the water-cooled nozzle. The workpiece is not connected to the power supply. The nozzle is both an electrode and a contraction function. The transfer type and the non-transfer type exist at the same time as the hybrid plasma arc, and the surfacing welding uses the hybrid and transfer plasma arc as the heat source.



When combined plasma arc surfacing welding is used, two independent DC arc welding machines are generally used as power sources to supply non-transferred arc and transferred arc respectively. The alloy powder is pre-heated in the arc column, in a molten or semi-melted state, sprayed into the molten pool of the workpiece, fully melted in the molten pool, and discharged gas and floating slag. By adjusting the transfer arc and non-transfer arc current, powder feeding amount and other process specification parameters, the melting of alloy powder and the heat transferred to the workpiece are controlled. With the relative movement of the welding gun and the workpiece, the alloy molten pool gradually solidifies, and a high-density, high-bonding strength surfacing structure is obtained on the workpiece.