To make aircrafts more economical, environmentally friendly and robust, Fraunhofer engineers from Dresden have developed a new ceramic heat shield technology. In this process, a powder of yttrium-stabilized zirconium oxide (YSZ) is added to water to form a suspension. Quickly and cost-effectively this liquid powder mixture can be sprayed onto turbine blades or other aircraft parts. Such and similar thermal barrier coatings (TBCs) facilitate aircraft engines, which consume less fuel and do not contaminate the atmosphere as much. Headed by Dr. Maria Barbosa a team from the Fraunhofer Institute for Material and Beam Technology IWS Dresden has now implemented the new technology into industrial application together with the Swiss plant manufacturer AMT. The IWS researchers see great potential for their suspension spraying process in the aerospace industry, but also in the semiconductor industry and many other sectors. “This allows high-quality and durable protective coatings even on large components at comparatively low cost,” emphasizes IWS engineer Dr. Barbosa. “By spraying suspensions instead of powder, we can use materials with very small particles, not previously suitable for this purpose. At this point, we establish a bridge between the state-of-the-art coating processes, all of which have their advantages and disadvantages. In the future, it will also be possible to process novel material compositions.” In order to generate such thermal barrier coatings, two technology paths are mainly used so far: Some companies process the components with electron beam evaporators (“EB-PVD”) in vacuum chambers. This results in very high-quality and durable coatings. But this process is expensive, especially for coating very large components. The second technology path involves atmospheric plasma spraying (APS). Powder is melted in a plasma jet and sprayed onto the component. APS is rather inexpensive because it does not require vacuum chambers. But the protective layers produced in this way are not as resistant.
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Source: Frauhofer IWS