Last year's shutdown of European airspace following a volcanic eruption in Iceland alerted everyone to the danger that ash clouds can pose to aircraft engines.
Now, researchers have discovered that a new class of ceramic coatings could offer jet engines special protection against volcanic ash damage in the future.
In a study led by Nitin Padture, a professor at the Ohio State University College of Engineering, researchers tested two coatings that originally were developed to keep airborne sand from damaging jet engines and found that the coatings also resist damage caused by small amounts of ash deposits.
However, large amounts of ash can temporarily jam a jet engine and cause it to stall, and these coatings would not be useful in those circumstances, Padture says.
Temperatures inside an engine can reach 2,500°F, and ceramic thermal-barrier coatings insulate metallic engine parts from that heat. Ingested ash melts onto and penetrates the coating. Upon cooling, the molten ash forms a brittle glass that flakes off, taking the coating with it.
Padture previously invented a coating composition to prevent similar engine damage caused by sand. Like sand, ash is made mostly of silica, and when the Icelandic volcano erupted in April 2010, it billowed clouds of silicate ash.
The research team experimented with a typical jet engine coating and two sand-resistant coatings, including Padture's formula (containing zirconia and alumina) and a commercially available formula based on gadolinium zirconate. In that test, the ash badly damaged the typical coating, while coatings made of Padture's formula and the gadolinium zirconate formula retained their overall structure. Both sand-resistant coatings are more expensive than the typical coating, but the researchers say that the benefits outweigh the cost.