Frequently Asked Questions
Coatings are generally used to confer a desired functionality to a substrate that fails to exhibit the function unaided. Ceramic coatings are usually applied to make the component:
- chemically more inert (corrosion resistant)
- impervious to liquids and gases
- harder
- more wear resistant
- insulating (electrically and thermally)
- more decorative
The type of coating and the method of deposition depend on a number of factors including:
- desired thickness
- substrate material and properties
- function of coating
- operating parameters of component
- geometry of area to be coated
- economic considerations
Ceramic coatings can be categorised in terms of thickness. Thick coatings can be deposited in numerous ways but the most common are thermal spraying and enamelling. Examples would be thermally sprayed alumina or tungsten carbide, or the enamel coatings on whitewares.
Thin coatings are usually deposited by vapour deposition (chemical and physical vapour deposition; CVD and PVD respectively). An example would be titanium nitride coatings on cutting tools; very distinctive because the coatings look like gold - but unlike gold, they are extremely hard (~2500Hv).
In addition, there is a wide range of other coating methods mostly based on the deposition and sintering of slurries. However, these 'wet' methods are 'small' on the industrial scene compared with the two main families.
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