Characteristics of thermal spraying technology

       

Characteristics of thermal spraying
technology

 

Characteristics of thermal spraying
technology: the application of thermal spraying technology has developed from
the preparation of decorative coatings to the preparation of various functional
coatings, such as wear-resistant, anti-corrosion, oxidation-resistant, heat
insulation, electrical conductivity, insulation, friction reduction,
lubrication, radiation protection and so on. Thermal spraying can be used for
both repair and manufacture. Because the performance of the coating material is
better than that of the substrate, the product quality can be greatly improved
by coating the surface of the parts with the coating material.

Selection of thermal spraying coating
materials:

(1) It is better for the thermal spraying
material to have a wide liquid region, which can keep the droplet of the
coating material in liquid phase for a long time.

(2) Good thermal stability, no sublimation
and no decomposition in high temperature flame. If the material is easy to decompose
at the temperature of thermal spraying, it is not suitable for thermal
spraying.

(3) The spraying material should have good
wettability with the substrate in the molten state, so as to ensure a good
bonding performance between the coating and the substrate.

(4) It has the similar coefficient of
thermal expansion with the base material, so as to prevent the larger thermal
stress due to the large difference of the coefficient of thermal expansion.

The formation process of thermal spraying
coating is as follows

(1) The spray material is heated to a
molten state.

(2) When the spray material is atomized
into tiny droplets and impinges on the surface of the substrate at high speed,
the greater the kinetic energy of the particles impinging on the substrate and
the greater the impact deformation, the better the coating bonding.

(3) The molten high-speed particles deform
after impacting the surface of the substrate and condense to form a coating.

Thermal spraying has become an important
method for the preparation of wear-resistant coating, which is widely used in
various fields of national economy. The porous layered structure of the coating
makes its wear-resistant service behavior significantly different from that of
the same kind of block. The most important feature is the influence of load.
Under low stress service conditions, the thermal spraying coating shows good
wear resistance, but when the stress is higher than a certain level, due to the
accelerated propagation of cracks along the interface of deposited particles,
the wear is accelerated, especially under the conditions of erosion,
cavitation, fretting, fatigue and abrasive wear, the potential of the coating
material can only play 10% - 30%. Therefore, it is an important way to make
full use of the material potential, improve the service efficiency of thermal
spraying coating and save resources and energy to establish the basic research
on the systematic relationship between the coating structure, performance,
service conditions and service efficiency, and to establish the database to
guide the design and use of wear-resistant coating.

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