Abradable Coating

Definition - What does Abradable Coating mean?

Abradable coatings are a type of coating made using abradable substances. This means that they have the tendency to wear when rubbed against a highly abrasive material, while leaving the underlying material damage free.

The main function of abradable coatings is to make automatic clearances adjustments possible in order to account for thermal fluctuations and other physical occurrences present in the operational lifespan of a certain device. This type of coating is widely used in settings involving turbo jet machinery. The clearance that exits between the casing and turbine fans or fan blade tips should account for concentricity variances and thermal expansion. In order to protect catastrophic tip-against-casing contact, large clearances should be facilitated.

Corrosionpedia explains Abradable Coating

Since the 1990s, the volume of air traffic has increased significantly, while the total volume of fuel consumed remains constant. Manufacturers of jet engines provide solutions by enhancing power generation and engine efficiency. This has been made possible by increasing operating temperatures with the aid of lightweight materials and improved aerodynamic design. The best solution to further improve efficiency is to lessen the clearance between the casing and turbine fans. With abradable coatings, this is achieved along with improving the surge margin, leading to increased engine flow safety and stability.

However, abradable coatings are not limited to aviation engines. They can be applied in almost any type of rotating equipment such as:

  • Radial compressors
  • Gas turbines
  • Pumps
  • Turbo chargers

In terms of aviation engine applications, abradable coatings work by reducing the clearance between the fan blade tip and casing. This can cause the turbine fans to rub next to the shroud. By using abradable coatings to cover the shroud, this phenomenon can be highly tolerated. These coatings are made to release all types of fine wear dirt and debris without causing blade wear.

Improvements in abradable coatings require various tests, extending from powder fabrication up to choosing the maximum thermal spray procedure. All of these are done in order to simulate field trials and laboratory testing. This results in abradable coating recognition by engine manufacturers. The objective is to create a protective seal that does not result in blade wear. Ideally, the abradables should work to preserve a smooth shroud facade that will remain intact for years.

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