Powder Flame Spraying Equipment

       

Powder flame spraying (PFS) is a thermal
spraying method using oxygen acetylene flame as heat source and powder as
spraying material. It is a kind of spraying method after flame wire spraying.
Because of the simple equipment and many kinds of spraying materials, it is the
most common thermal spraying process in China.

1. Spraying principle

Powder flame spraying is carried out by
means of powder flame spray gun. Oxygen and acetylene are respectively
introduced into the spray gun through the siphon gas head, and the combustion
flame is generated at the nozzle outlet after mixing the two. The spray gun is
equipped with a powder bucket or powder inlet. The powder in the powder bucket
is pumped by the negative pressure generated by the air flow, so that the
powder is ejected from the center of the nozzle into the flame with the air
flow, and is heated or softened. The flame flow pushes the molten particles to
spray to the surface of the workpiece at a certain speed to form a coating. In
order to improve the flight speed of particles, some spray guns are equipped
with compressed air nozzles, which provide additional thrust to particles with
the help of compressed air.

In the process of heating, the powder melts
from the surface to the core. The melted surface tends to be spherical under
the action of surface tension, and there is no atomization process of powder
particle being broken again. Therefore, the size of powder particles determines
the size and surface roughness of deformed particles in the coating to a
certain extent. When the powder is heated and accelerated by the flame flow,
because the position of the powder in the flame flow is different, the degree
of heating is different, some are melted or semi melted, some are only softened
or semi softened. This is quite different from the melting atomization process
of wire flame spraying, which makes the bonding strength and compactness of
powder flame spraying coating generally inferior to wire flame spraying.

2. Equipment

The composition of powder flame spraying
equipment is similar to wire flame spraying, which is also composed of oxygen
acetylene supply system, compressed air supply system, spray gun, etc. The
difference is mainly in the spray gun. When the spray gun does not need
compressed air, the compressed air supply system is not needed. In the case of
powder feeding outside the gun, it is necessary to increase the powder feeder.

There are many kinds of powder flame
spraying guns. The representative domestic spray guns are: qt-e-7 / h and
qt-e2000-7h spray guns made in Shanghai, cp-3000 subsonic spray guns made in
Chengdu, and 5p and 6p spray guns imported from Metco. Although there are some
differences in the structure of different types of spray guns, they are
basically composed of flame combustion system and powder supply system.

Cp-3000 subsonic spray gun is a kind of
high-speed and efficient powder spraying gun, which uses oxygen acetylene flame
as heat source and compressed air as powder feeding gas, accelerating gas and
cooling gas. It has a unique spiral mixing and injection intake structure,
which can greatly improve the combustion efficiency and power of the flame
flow. By selecting different nozzle components, the spray gun can spray carbide
coating with excellent performance and high melting point material coating such
as alumina and zirconia.