Characteristics Of Plasma Transfer Arc Surfacing

       

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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