Ceramic Coatings

Ceramic coatings are are available in several various types, consisting of different compositions and exhibiting different mechanical and metallurgical properties. These coatings offer superior properties over most materials when used for coatings. The application method is also significant, as it affects the properties of the material. When applied through thermal spray techniques including flame, electric arc, vacuum or plasma assisted thermal spraying or high velocity oxy-fuel (HVOF), the ceramic coatings usually possess good adhesion with the base material, due to the associated high temperature or high velocity, offering superior diffusion and strong bonding respectively. In addition, a dense coating is obtained with minimal waste of coating material.

Selection Criteria

The use of any ceramic coating depends on the desired performance properties. Different ceramic coatings offer different properties, found below. Using these properties, the proper coating material can be selected. Another key parameter for selection is the budget and economic consideration for any coating application.

Properties of Ceramic Coatings

Good durability
Superior hardness
Excellent resistance to wear, scratching and abrasion
Good oxidation resistance due to formation of high melting temperature oxides
Superior UV protection
Good corrosion resistance due to formation of passive oxide layer
Prevention from chemical attack
Low porosity

Specific Types of Ceramic Coatings

Chrome Oxide (Cr₂O₃) coatings usually offer good resistance to wear and corrosion.
Zirconia (ZrO₂) offers superior thermal barrier properties due to the presence of thermally stable oxide. Hence, it is especially beneficial for high temperature applications. It also drastically improves the fatigue and creep life of the part resulting in extended service life.
Alumina (Al₂O₃) coatings, or quartz coatings, are inexpensive and can be applied to any material for thermal or electrical insulation and has good a combination of wear and corrosion resistance.
Titania (TiO₂) coatings offer excellent wear resistance while being inexpensive and chemically stable. They are often applied in when hard surfaces and wearing are involved.
Alumina-Titania (Al₂O₃/TiO₂) composite coatings, usually consisting of a small composition of Titania, offers a combination of good corrosion and chemical resistance in many applications including underwater and marine environments. The addition of Titania (approx. 3%) considerably imparts greater toughness to the coating.

Potential Benefits

They enhance the life span of the part by imparting their specified properties and hence, improve the service life.
Provide good thermal and electrical insulation.
Reduces the need for part replacement and frequent maintenance.

Uses and Applications

The uses and applications of ceramic coatings greatly depends on the type of ceramic coating. Different coatings have different applications which are widespread across various industries. Some areas include:

In the textile industry for use in heating plates and rollers where good wear resistance is required.
In the automobile industry for coating of the vehicle frame to impart wear and scratch resistance and hydrophobicity. High end coatings are used on race cars.
In the defense sector for underwater applications where good chemical and corrosion resistance is required.