Compared with other surfacing methods such as oxyacetylene flame surfacing and electrode arc surfacing, plasma surfacing has many advantages.
(1) High productivity. Plasma arc surfacing process is carried out under automatic control, which has high productivity and high deposition rate. At present, the foreign high-power plasma arc surfacing current is as high as 500A, and the deposition rate can reach 12kg / h.
(2) The dilution ratio of base metal to alloy is low. Because there are many adjustable specification parameters in the process, it can actively control the heat input. The alloy powder is pre heated in the arc column and transits to the molten pool in a spray shape, which has a buffer effect on the arc blowing force, and the molten pool is heated evenly. Therefore, the melting depth of the base metal can be controlled and the dilution rate of the base metal to the alloy can be reduced.
(3) The surfacing layer is well formed. Plasma arc surfacing is generally protected by argon, and the surfacing layer is flat and smooth. By changing the process specification parameters, the forming size can be accurately controlled and the size range is wide.
(4) The spray welding layer has good quality and process stability. Due to the good stability of plasma arc, the interference of external factors has little influence on electrical parameters and arc stability, so the process is easy to be stable. Due to the high plasma arc temperature, heat concentration, fast spray welding speed and one-time melting, the heat affected zone of the workpiece is small, the alloy structure grain of the spray welding layer is fine, the hardness and chemical composition are uniform, and the quality of the spray welding layer is good.
(5) The alloy powder is easy to prepare and has a wide range of materials. The temperature of plasma arc area is as high as (1.0-5.0) × L0k, so various metals can be overlaid. The alloy powder for surfacing is directly atomized into spherical powder after melting, which is easy to prepare. It can be melted into alloy powder with different components according to the required formula to obtain alloy fusion welding layers with different properties, so as to meet the requirements of surface properties of parts under different conditions. There are many kinds of spray welding alloy materials, including cobalt base, nickel base, iron base, copper base, etc. Generally, the alloys with high hardness, wear resistance, high temperature resistance and corrosion resistance are difficult to be made into wire rod and surfacing by other process methods, but it is easy to make these alloys into powder by plasma spray welding.
(6) Good controllability. The arc parameters such as atmosphere and temperature of plasma arc can be adjusted by changing power, gas type, flow and nozzle structure size, so as to realize efficient automatic production.
(7) The temperature of the workpiece to be overlaid is low and generally not easy to deform. In order to further reduce the temperature of the workpiece during overlaying, gas can also be used to cool the workpiece.
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