Polishing after thermal spraying

On this page, we will explain thermal spraying and polishing after thermal spraying.

What is thermal spraying

Thermal spraying is a processing technology that sprays materials such as ceramics, metals, and cermets that have been melted or semi-molten by applying heat to form a functional coating on the substrate surface.

Purpose and application of thermal spraying

Thermal spraying can form the following functional coatings by selecting the materials used.

• rust prevention
  … It is a treatment that can prevent rusting, which also affects durability.
• Corrosion protection
  … It is a treatment that can prevent oxidation and corrosion due to high temperatures and various corrosive environments.
• Wear resistance
  … It can be more resistant to all types of wear, such as rubbing and scuffing.
• Heat resistance/heat insulation
  … It is a treatment that can maintain the shape and function in a high temperature environment.
• Shock resistance
  … It can increase the durability against external impacts.
• Chemical resistance
  … Prevents chemical reactions when the object comes into contact with chemicals.
• Electrical insulation
  … It is possible to impart a property that does not allow electricity to pass through, which is called electrical insulation.
• Dimensional restoration
  … It is to repair and restore the dimensions of worn, damaged or worn parts.

Thermal spraying is a technology used in a variety of fields, including semiconductors, space, aviation, power generation, printing, and automotive parts.

It is a technology that can serve as a foundation in the manufacturing industry, and new coating technologies are still being developed every day.

Thermal spray type

Thermal spraying is broadly classified into “gas thermal spraying” and “electrical thermal spraying” depending on the type of heat source that applies heat.

Furthermore, it is subdivided according to the heating method, and the most suitable method is selected according to the material and form used for thermal spraying, the type of object, purpose, etc.

Typical forms of heating are as follows.

Heat source type	heating form	overview
gas spraying	Flame spraying	It is a method of forming a film by heat using a combustion flame of fuel and oxygen gas as a heat source.
	High speed flame spraying	In this method, the combustion energy pressure of flame spraying is strengthened and a high-density coating is formed by colliding with the base material at high speed.
	Explosive spraying	It is a method of forming a highly adhesive film by explosively burning a fuel gas consisting of acetylene and oxygen.
electric thermal spray	Arc spraying	It is a thermal spraying method in which an arc discharge is generated at the tip of two metal wires/wires, and the material melted by the discharge energy is sprayed with compressed air.
	Plasma spraying	It is a thermal spraying method that uses a high-temperature plasma jet to spray the thermal spray material at a speed exceeding the speed of sound.

Process of thermal spraying

1．Cleaning of objects to be sprayed

For the purpose of making it easier to bond the object and the thermal spray material and to prevent the object from getting dirty, the cleaning work is performed as a pre-process.

For cleaning, “solvent cleaning” and “water-soluble cleaning” are used to remove dirt such as mineral oil, and oils and fats are removed by heating.

2．Surface roughening treatment (blasting)

Roughening treatment (blasting) is, as the name suggests, a process that creates a rough surface on the surface of an object.

An oxide film, rust, paint film, etc. adhere to the surface of the object.

Scraping off these roughens the surface, making it easier to adhere and fix with the thermal spray material.

3．Coating/thermal spraying

Depending on the purpose and application, the above-mentioned “gas spraying” and “electric spraying” are performed.

4．Heat treatment

This is not an essential process, it may be performed for the purpose of improving properties such as strength, density, corrosion resistance, and hardness of the film.

5．Sealing treatment

Pore-sealing is a process that fills the fine pores contained in the film.

Pores can lead to large defects during thermal spraying for purposes such as corrosion protection.

In addition, since the pores are sealed by the sealing agent, the surface becomes smooth, and the effect of keeping the thermal spray coating for a long time can be expected.

6．finishing

The coating surface as it is thermally sprayed is rough and rough.

Depending on the purpose of use, precision finishing, more accurate dimensional accuracy, and in order to increase smoothness, cutting, abrasive processing, and polishing are performed.

Need for polishing after thermal spraying

After thermal spraying, the surface becomes rough, but it can be polished to a mirror finish.

• After thermal spraying, the surface becomes rough, but it can be polished to a mirror finish.
• In addition to mirror finishing, polishing is also effective for the purpose of finishing to the desired thickness, such as suppressing variations in the thickness of the thermal spray coating.
• By preparing the flatness and parallelism of the base material in advance, we can achieve a higher level of combined precision such as flatness, parallelism, dimensional tolerance, and surface roughness in the polishing process after thermal spraying. Finished to perfection.

Thermal spray coating material with a proven track record

Al2O3
Forsterite
cordierite
steatite
Inconel
Monel
Spinel
Hastelloy
WC Carbide
Yttrium fluoride (YF3)
Yttrium oxide (Y2O3)
MCrAlY thermal spray
Dozens of other types

We have a track record of processing various types of thermal spray products.

Please consult TDC for precision polishing after thermal spraying.

As mentioned above, it is common to perform polishing in the post-process of thermal spraying.

In recent years, the number of customers and needs that require even higher precision surface roughness for polishing after thermal spraying has increased, and the number of cases where we are asked to do so is also increasing.

If you require precision polishing after thermal spraying, please feel free to contact us.

Related page