THERMAL SPRAY COATING
Definition
:
Thermal spraying is generic term used to define a group of
processes that deposit finely divided metallic or nonmetallic
materials onto a prepared substrate to form a coating.
The coating
material may be in powder, rod or wire form. The Thermal Spray
gun uses plasma arc, combustible gases or an electric arc
to generate the heat necessary to melt the coating material.
The material changes to a plastic or molten state when heated
and is accelerated by process gases. The acceleration of the
molten material produces a confined stream of particles that
the process gases transfer to the substrate. The particles
strike the substrate, flatten upon impact, and form thin platelets
that bond to the substrate and to each other. The particles
build up and cool into a lamellar structure that forms a coating.
The Thermal
Spray process is synergistic. System components, parameters
and the desired coating functions and properties must be determined
to select the type of material and equipment needed for the
process. The process may be tailored for particular application
after establishing this information. Various coatings can
be achieved by using different combinations of equipment and
consumables. Basic Thermal Spray systems typically consist
of a spray gun, powder supply or gas control console and a
wire or powder feeder.
Thermal Spray
History :
Thermal Spray is one of the coating process which is defined
a group of process that burnt / melted the material (Powder;
wire; rod) with heat sources (could be flame/electricity)
and then after perfectly melted the compressed air will blow
this melting material become “splat” and hit the
prepared surface and produce a coating surface.
Thermal Spray
is a cold process, since the work piece temperature during
spraying no more than 200oC.
The first
time Thermal Spray was developed by Dr. Max Ulrick Shoop from
Zurich, he was recognized the possibility that a stream of
molten particles impinging upon themselves could create a
coating.
Followed by
Dr. M.U. Schoop in the early 1900 developed equipment and
techniques for producing coatings using molten and powder
metals.
In about 1912,
his produced the first instrument for spraying solild metal
in wire form, and the development of thermal spray began.
