New Ceramic Coating in Jet Engines To Protect Damage From Volcanic Ash

Last year, the whole of the European air got filled with the volcanic ash from the volcanic eruption at Eyjafjallajökull in Iceland. The airline industry came to a standstill as the flights all across the continent were stalled. A lot of people were left stranded in foreign countries and away from home in the festive season. The main reason for canceling the flights was that the clouds of volcanic ash damaged the jet engines making them dysfunctional in the middle of the journey. Lots of people believed that low visibility was the major challenge faced by the pilots in these conditions. But it is not true as visibility is not so much responsible for the huge amount of revenue losses incurred on the airlines. The ash can jam the engines causing the planes to crash. The European aerospace shutdown loss was estimated to be more than $ 2 billion!

Now, the scientists have created a new type of ceramic coating that can be used to save the #-Link-Snipped-#engines from the volcanic gases. In a recent study that was published in the online version of science journal Advanced Materials, the team of scientists experimented with two classes of ceramic coating which had been previously used for securing the engines against the sand particles that accumulate in the aircraft turbines. And guess what, the thing works similarly for the volcanic ash clouds also! The group of scientists is led by Dr. Nitin Padture, College of Engineering Distinguished Professor at the Ohio State University. He feels that prevention is the best cure. But when it is not feasible to take preventive measures, the ceramic coating can check the damage done due to the ash particles deposited on the inside of engines.

The basic principle behind the engine damage to ceramic heat barrier coatings is that when the temperature inside the engine very high (nearly 2500ºF), then the ceramic layer insulates the metal parts from the extreme heat. If volcanic ash is ingested, it melts at such great temperatures and penetrates the coating. On cooling, the ash particles turn into a glass like substance which corrodes off the engine surface along with the coating.

Ash has a chemical composition similar to sand as both have silica as a dominant component. But the difference in their composition arises because ash from different volcanoes has different chemical structure. The main reason behind the study was to check whether the ceramic layer reacts in the same way on these particles and how efficient is this defense mechanism. For the purpose, post graduate students Julie Drexler and Andrew Gledhill coated three metal parts with different ceramic layers. One was coated with the normal ceramic heat barrier coating. Next one used the special formulated layer by Padture consisting of Zirconia and Alumina and the last piece was treated with a coating which is commercially available (Gadolinium Zirconate).All the sample parts were heated in a furnace to high temperature so as to simulate the heat in a jet engine. It was observed that the first sample got damaged while the remaining two were able to sustain the ash. When the cross sections of all the three samples were seen under the microscope, it was seen that the ash particles had penetrated deep into the normal ceramic coating but couldn’t penetrate the other two sand resisting coatings to that much extent. This is the reason behind the protective action is that there is a chemical reaction in the ceramic layer which prevents the ash particles from entering into the layer. Due to the open pores, the layer retains its expansion and contraction when it is heated and cooled. The scientists are confident that these silicate resistive coatings will help solve the problems of a lot of aircraft engines.

Image Credit: Christian Science Monitor - CSMonitor.com