Reserch & Development

Thermal spraying

Thermal spraying is a surface modification technology in which metals and ceramics are heated to a molten or semi-molten state and then made to collide with and accumulate on the surface of a substrate thereby forming a coating.

Thermal spraying means to cause a molten material to collide with and accumulate on the surface of a substrate. Accordingly, in order to create a good thermal spray coating, a high-temperature state to create a sufficient molten state and a high-speed state to spray particles are required. In the film-creation process in thermal spraying, molten particles collide with the substrate and simultaneously become flattened. Some particles become a spray and are scattered. Particles of the raw material that have melted and become a liquid, build up rapidly to form a film.

Various Thermal spraying Methods

Water plasma spraying

Gas plasma spraying

High-velocity oxygen fuel spraying

Arc spraying

Flame spraying

Details of each thermal spraying method

Characteristics of Thermal spraying Methods

Thermal spraying, which involves the unique process of melting and projecting a solid feedstock, has characteristics that are unlike other surface modification technologies. This section provides descriptions of various surface modification technologies including thermal spraying.

Comparison of surface modification technologies

Method	Coating materials	Substrate materials	Degree of adhesion
Thermal spraying	Metals, alloys, ceramics, plastics, glass, Cermet	Metals, ceramics, plastics, wood, paper products	Excellent
Plating	Metals, alloys	Materials that cannot be soaked in the plating solution	Good
CVD (Chemical Vapor Deposition)	Heat-resistant metals, ceramics, sulfides, selenium compounds, and others	Materials capable of withstanding 500～2000℃and chemical corrosion by deposits	Good
Vacuum deposition	Pure metals, alloys, compounds	Any non-gas-emitting surface	Good Good when substrate heated. Excellent when substrate sputtered.
Ion plating	Pure metals, alloys, carbides, nitrides, oxides	Same as above	Excellent

Advantages and Disadvantages of thermal spraying

Advantages of thermal spraying

Wide selection of spray materials.
Wide selection of substrate materials.
Speed of coating formation is fast.
Wide range of substrate dimensions.
On-site work possible.
Coating can be formed while keeping substrate at low temperature.
Spraying is a dry process so environmental impact is low.

Disadvantages of thermal spraying

Thermal spray coating does not always indicate the characteristics of the original material.
Thick coatings are difficult to achieve.
Low degree of adhesion (spray efficiency) on small substrates and substrates with small curvature.
The coating formation process is not sufficiently clear and the relationship between the causes (parameters) of the application process and coating characteristics is also unexplained.
There is no evaluation method (testing method) for assessing how well the coating has adhered to the substrate.
Requires measures to combat noise, light, dust, fumes, and other issues.

F A Q

Frequently asked questions
related to our R&D(Thermal spraying).

Can you perform thermal spraying on-site at heat power plants outside Japan?

What kind of substrate materials can thermal spraying be used on?

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