Jet engines are one of the most astonishing achievements in human engineering history. However, Ben Beake, head of materials research at “Micro Materials,” a testing instrument company, pointed out that jet engines were not supposed to exist. “The temperature of the air entering is higher than the melting point of the metal – this is clearly not a good thing,” he said, noting that the air temperature can reach over 1,000°C.
Designers of jet engines have addressed this issue by applying heat-resistant ceramic coatings to the engine blades. Today, researchers are developing even stronger coatings to allow engines to operate at higher temperatures.
“If we can make the engine operate at higher temperatures, it will significantly save fuel and reduce carbon dioxide emissions,” Dr. Beake stated. He estimated that simply raising the temperature by about 30°C could save 8% of fuel.
This is the advantage of coatings, as they completely change the performance of the materials they protect. While few realize their importance, these coatings and films provide strong support for high-performance machinery and ensure expensive equipment operates smoothly in harsh environments.
Dr. Beake and his colleagues’ mission is to push coatings to their limits to test and evaluate their durability and effectiveness. Not all of their clients always get the test results they hope for. He recalled telling a missile manufacturer a few years ago, “We’ve destroyed your coating.” “They stormed out,” Dr. Beake said.
In addition to exposing coatings to high temperatures, Micro Materials also has a “woodpecker” device, a tiny diamond pen tip that randomly taps on different areas of the coating to test its durability.
Recently, the company collaborated with the UK’s Teer Coatings to test a product that can be applied to satellite components, including gears and bearings for various moving parts.
Xiaoling Zhang from the company stated that the challenge lies in the fact that coatings must resist dust particles and radiation in space after being exposed to atmospheric humidity on the ground before launch. However, she claimed that the company has achieved the expected results.
Besides protecting spacecraft, coatings can also prevent astronauts from getting sick.
Biofilms are viscous bacterial accumulations inside pipelines that grow faster in low gravity environments, posing potential issues for water sources on space stations or mechanical components transporting fluids on future spacecraft.
“We know that biofilms can lead to mechanical failures,” said Kripa Varanasi from the Massachusetts Institute of Technology. “This is something we want to avoid.”
Professor Varanasi and his colleagues developed a series of coatings that make surfaces smooth to resist biofilm formation. An experiment conducted on the International Space Station confirmed the effectiveness of one such coating.
The idea behind these coatings is to mix solid materials with lubricants, then spray them inside pipelines to make the internal surfaces extremely smooth.
Professor Varanasi gained attention for developing similar coatings used inside toothpaste packaging to allow users to squeeze out every drop of toothpaste. He and his colleagues commercialized this technology through their derivative company, LiquiGlide.
Slipperiness may be an underrated quality. Nuria Esparagas and her colleagues at the Norwegian University of Science and Technology developed a silicon carbide-based coating specifically for aluminum manufacturing or repair equipment.
This coating, similar to the effect of a non-stick pan, prevents molten aluminum from sticking to expensive equipment. However, the exact operation of this specific coating remains somewhat mysterious.
“Honestly, we don’t know how it works, its mechanism is still unknown,” Professor Esparagas stated.
Nonetheless, this coating has been commercialized through her derivative company, Seram Coatings. Atlas Machine and Supply in the US, specializing in manufacturing and repairing industrial machinery, has tested this coating.
“The real benefit is extending the life of tools and improving product quality,” Chief Innovation Officer Jeremy Redberg said.
He noted that without this coating, Atlas had to rebuild roller tools used for processing aluminum every two days, costing $4.5 million annually. With the new coating, the tools’ lifespan has extended to a whole week, reducing rebuilding costs to around $1.3 million per year.
Coatings can achieve remarkable effects but don’t always work as expected, noted Andy Hopkinson, Managing Director of the Safinah Group, a company often called in to investigate coating failures.
“We’re seeing a lot of issues in car parks right now, their passive fire protection systems are peeling off,” he referred to fire-resistant coatings applied to concrete structures.
His company has also found that coatings applied to commercial vessels don’t always prevent barnacles and other marine organisms from attaching to the hull. This problem, known as biofouling, increases friction, meaning the vessel’s engines have to work harder and consume more fuel.
While coatings can help solve such problems, ship owners don’t always choose the right coatings for their vessels. Dr. Hopkinson stated that this decision should depend on factors such as the vessel’s sailing location, expected idle time, rather than operating time.
The cost of repairing such problems can amount to thousands or even millions of pounds. “Usually, the cost of paint is 1% to 2% of the total project cost. The issue is when it goes wrong, the cost exponentially increases,” Mr. Hopkinson said.
Nevertheless, researchers in the field point out that there are still many opportunities to improve existing coatings and develop new ones, which have the potential to significantly enhance the performance of machinery or infrastructure in the future.